1 /*-------------------------------------------------------------------------
4 * Selectivity functions and index cost estimation functions for
5 * standard operators and index access methods.
7 * Selectivity routines are registered in the pg_operator catalog
8 * in the "oprrest" and "oprjoin" attributes.
10 * Index cost functions are located via the index AM's API struct,
11 * which is obtained from the handler function registered in pg_am.
13 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
14 * Portions Copyright (c) 1994, Regents of the University of California
18 * src/backend/utils/adt/selfuncs.c
20 *-------------------------------------------------------------------------
24 * Operator selectivity estimation functions are called to estimate the
25 * selectivity of WHERE clauses whose top-level operator is their operator.
26 * We divide the problem into two cases:
27 * Restriction clause estimation: the clause involves vars of just
29 * Join clause estimation: the clause involves vars of multiple rels.
30 * Join selectivity estimation is far more difficult and usually less accurate
31 * than restriction estimation.
33 * When dealing with the inner scan of a nestloop join, we consider the
34 * join's joinclauses as restriction clauses for the inner relation, and
35 * treat vars of the outer relation as parameters (a/k/a constants of unknown
36 * values). So, restriction estimators need to be able to accept an argument
37 * telling which relation is to be treated as the variable.
39 * The call convention for a restriction estimator (oprrest function) is
41 * Selectivity oprrest (PlannerInfo *root,
46 * root: general information about the query (rtable and RelOptInfo lists
47 * are particularly important for the estimator).
48 * operator: OID of the specific operator in question.
49 * args: argument list from the operator clause.
50 * varRelid: if not zero, the relid (rtable index) of the relation to
51 * be treated as the variable relation. May be zero if the args list
52 * is known to contain vars of only one relation.
54 * This is represented at the SQL level (in pg_proc) as
56 * float8 oprrest (internal, oid, internal, int4);
58 * The result is a selectivity, that is, a fraction (0 to 1) of the rows
59 * of the relation that are expected to produce a TRUE result for the
62 * The call convention for a join estimator (oprjoin function) is similar
63 * except that varRelid is not needed, and instead join information is
66 * Selectivity oprjoin (PlannerInfo *root,
70 * SpecialJoinInfo *sjinfo);
72 * float8 oprjoin (internal, oid, internal, int2, internal);
74 * (Before Postgres 8.4, join estimators had only the first four of these
75 * parameters. That signature is still allowed, but deprecated.) The
76 * relationship between jointype and sjinfo is explained in the comments for
77 * clause_selectivity() --- the short version is that jointype is usually
78 * best ignored in favor of examining sjinfo.
80 * Join selectivity for regular inner and outer joins is defined as the
81 * fraction (0 to 1) of the cross product of the relations that is expected
82 * to produce a TRUE result for the given operator. For both semi and anti
83 * joins, however, the selectivity is defined as the fraction of the left-hand
84 * side relation's rows that are expected to have a match (ie, at least one
85 * row with a TRUE result) in the right-hand side.
87 * For both oprrest and oprjoin functions, the operator's input collation OID
88 * (if any) is passed using the standard fmgr mechanism, so that the estimator
89 * function can fetch it with PG_GET_COLLATION(). Note, however, that all
90 * statistics in pg_statistic are currently built using the database's default
91 * collation. Thus, in most cases where we are looking at statistics, we
92 * should ignore the actual operator collation and use DEFAULT_COLLATION_OID.
93 * We expect that the error induced by doing this is usually not large enough
94 * to justify complicating matters.
103 #include "access/gin.h"
104 #include "access/htup_details.h"
105 #include "access/sysattr.h"
106 #include "catalog/index.h"
107 #include "catalog/pg_am.h"
108 #include "catalog/pg_collation.h"
109 #include "catalog/pg_operator.h"
110 #include "catalog/pg_opfamily.h"
111 #include "catalog/pg_statistic.h"
112 #include "catalog/pg_type.h"
113 #include "executor/executor.h"
114 #include "mb/pg_wchar.h"
115 #include "nodes/makefuncs.h"
116 #include "nodes/nodeFuncs.h"
117 #include "optimizer/clauses.h"
118 #include "optimizer/cost.h"
119 #include "optimizer/pathnode.h"
120 #include "optimizer/paths.h"
121 #include "optimizer/plancat.h"
122 #include "optimizer/predtest.h"
123 #include "optimizer/restrictinfo.h"
124 #include "optimizer/var.h"
125 #include "parser/parse_clause.h"
126 #include "parser/parse_coerce.h"
127 #include "parser/parsetree.h"
128 #include "utils/builtins.h"
129 #include "utils/bytea.h"
130 #include "utils/date.h"
131 #include "utils/datum.h"
132 #include "utils/fmgroids.h"
133 #include "utils/index_selfuncs.h"
134 #include "utils/lsyscache.h"
135 #include "utils/nabstime.h"
136 #include "utils/pg_locale.h"
137 #include "utils/rel.h"
138 #include "utils/selfuncs.h"
139 #include "utils/spccache.h"
140 #include "utils/syscache.h"
141 #include "utils/timestamp.h"
142 #include "utils/tqual.h"
143 #include "utils/typcache.h"
146 /* Hooks for plugins to get control when we ask for stats */
147 get_relation_stats_hook_type get_relation_stats_hook = NULL;
148 get_index_stats_hook_type get_index_stats_hook = NULL;
150 static double var_eq_const(VariableStatData *vardata, Oid operator,
151 Datum constval, bool constisnull,
153 static double var_eq_non_const(VariableStatData *vardata, Oid operator,
156 static double ineq_histogram_selectivity(PlannerInfo *root,
157 VariableStatData *vardata,
158 FmgrInfo *opproc, bool isgt,
159 Datum constval, Oid consttype);
160 static double eqjoinsel_inner(Oid operator,
161 VariableStatData *vardata1, VariableStatData *vardata2);
162 static double eqjoinsel_semi(Oid operator,
163 VariableStatData *vardata1, VariableStatData *vardata2,
164 RelOptInfo *inner_rel);
165 static bool convert_to_scalar(Datum value, Oid valuetypid, double *scaledvalue,
166 Datum lobound, Datum hibound, Oid boundstypid,
167 double *scaledlobound, double *scaledhibound);
168 static double convert_numeric_to_scalar(Datum value, Oid typid);
169 static void convert_string_to_scalar(char *value,
172 double *scaledlobound,
174 double *scaledhibound);
175 static void convert_bytea_to_scalar(Datum value,
178 double *scaledlobound,
180 double *scaledhibound);
181 static double convert_one_string_to_scalar(char *value,
182 int rangelo, int rangehi);
183 static double convert_one_bytea_to_scalar(unsigned char *value, int valuelen,
184 int rangelo, int rangehi);
185 static char *convert_string_datum(Datum value, Oid typid);
186 static double convert_timevalue_to_scalar(Datum value, Oid typid);
187 static void examine_simple_variable(PlannerInfo *root, Var *var,
188 VariableStatData *vardata);
189 static bool get_variable_range(PlannerInfo *root, VariableStatData *vardata,
190 Oid sortop, Datum *min, Datum *max);
191 static bool get_actual_variable_range(PlannerInfo *root,
192 VariableStatData *vardata,
194 Datum *min, Datum *max);
195 static RelOptInfo *find_join_input_rel(PlannerInfo *root, Relids relids);
196 static Selectivity prefix_selectivity(PlannerInfo *root,
197 VariableStatData *vardata,
198 Oid vartype, Oid opfamily, Const *prefixcon);
199 static Selectivity like_selectivity(const char *patt, int pattlen,
200 bool case_insensitive);
201 static Selectivity regex_selectivity(const char *patt, int pattlen,
202 bool case_insensitive,
203 int fixed_prefix_len);
204 static Datum string_to_datum(const char *str, Oid datatype);
205 static Const *string_to_const(const char *str, Oid datatype);
206 static Const *string_to_bytea_const(const char *str, size_t str_len);
207 static List *add_predicate_to_quals(IndexOptInfo *index, List *indexQuals);
211 * eqsel - Selectivity of "=" for any data types.
213 * Note: this routine is also used to estimate selectivity for some
214 * operators that are not "=" but have comparable selectivity behavior,
215 * such as "~=" (geometric approximate-match). Even for "=", we must
216 * keep in mind that the left and right datatypes may differ.
219 eqsel(PG_FUNCTION_ARGS)
221 PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
222 Oid operator = PG_GETARG_OID(1);
223 List *args = (List *) PG_GETARG_POINTER(2);
224 int varRelid = PG_GETARG_INT32(3);
225 VariableStatData vardata;
231 * If expression is not variable = something or something = variable, then
232 * punt and return a default estimate.
234 if (!get_restriction_variable(root, args, varRelid,
235 &vardata, &other, &varonleft))
236 PG_RETURN_FLOAT8(DEFAULT_EQ_SEL);
239 * We can do a lot better if the something is a constant. (Note: the
240 * Const might result from estimation rather than being a simple constant
243 if (IsA(other, Const))
244 selec = var_eq_const(&vardata, operator,
245 ((Const *) other)->constvalue,
246 ((Const *) other)->constisnull,
249 selec = var_eq_non_const(&vardata, operator, other,
252 ReleaseVariableStats(vardata);
254 PG_RETURN_FLOAT8((float8) selec);
258 * var_eq_const --- eqsel for var = const case
260 * This is split out so that some other estimation functions can use it.
263 var_eq_const(VariableStatData *vardata, Oid operator,
264 Datum constval, bool constisnull,
271 * If the constant is NULL, assume operator is strict and return zero, ie,
272 * operator will never return TRUE.
278 * If we matched the var to a unique index or DISTINCT clause, assume
279 * there is exactly one match regardless of anything else. (This is
280 * slightly bogus, since the index or clause's equality operator might be
281 * different from ours, but it's much more likely to be right than
282 * ignoring the information.)
284 if (vardata->isunique && vardata->rel && vardata->rel->tuples >= 1.0)
285 return 1.0 / vardata->rel->tuples;
287 if (HeapTupleIsValid(vardata->statsTuple))
289 Form_pg_statistic stats;
297 stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
300 * Is the constant "=" to any of the column's most common values?
301 * (Although the given operator may not really be "=", we will assume
302 * that seeing whether it returns TRUE is an appropriate test. If you
303 * don't like this, maybe you shouldn't be using eqsel for your
306 if (get_attstatsslot(vardata->statsTuple,
307 vardata->atttype, vardata->atttypmod,
308 STATISTIC_KIND_MCV, InvalidOid,
311 &numbers, &nnumbers))
315 fmgr_info(get_opcode(operator), &eqproc);
317 for (i = 0; i < nvalues; i++)
319 /* be careful to apply operator right way 'round */
321 match = DatumGetBool(FunctionCall2Coll(&eqproc,
322 DEFAULT_COLLATION_OID,
326 match = DatumGetBool(FunctionCall2Coll(&eqproc,
327 DEFAULT_COLLATION_OID,
336 /* no most-common-value info available */
339 i = nvalues = nnumbers = 0;
345 * Constant is "=" to this common value. We know selectivity
346 * exactly (or as exactly as ANALYZE could calculate it, anyway).
353 * Comparison is against a constant that is neither NULL nor any
354 * of the common values. Its selectivity cannot be more than
357 double sumcommon = 0.0;
358 double otherdistinct;
360 for (i = 0; i < nnumbers; i++)
361 sumcommon += numbers[i];
362 selec = 1.0 - sumcommon - stats->stanullfrac;
363 CLAMP_PROBABILITY(selec);
366 * and in fact it's probably a good deal less. We approximate that
367 * all the not-common values share this remaining fraction
368 * equally, so we divide by the number of other distinct values.
370 otherdistinct = get_variable_numdistinct(vardata, &isdefault) - nnumbers;
371 if (otherdistinct > 1)
372 selec /= otherdistinct;
375 * Another cross-check: selectivity shouldn't be estimated as more
376 * than the least common "most common value".
378 if (nnumbers > 0 && selec > numbers[nnumbers - 1])
379 selec = numbers[nnumbers - 1];
382 free_attstatsslot(vardata->atttype, values, nvalues,
388 * No ANALYZE stats available, so make a guess using estimated number
389 * of distinct values and assuming they are equally common. (The guess
390 * is unlikely to be very good, but we do know a few special cases.)
392 selec = 1.0 / get_variable_numdistinct(vardata, &isdefault);
395 /* result should be in range, but make sure... */
396 CLAMP_PROBABILITY(selec);
402 * var_eq_non_const --- eqsel for var = something-other-than-const case
405 var_eq_non_const(VariableStatData *vardata, Oid operator,
413 * If we matched the var to a unique index or DISTINCT clause, assume
414 * there is exactly one match regardless of anything else. (This is
415 * slightly bogus, since the index or clause's equality operator might be
416 * different from ours, but it's much more likely to be right than
417 * ignoring the information.)
419 if (vardata->isunique && vardata->rel && vardata->rel->tuples >= 1.0)
420 return 1.0 / vardata->rel->tuples;
422 if (HeapTupleIsValid(vardata->statsTuple))
424 Form_pg_statistic stats;
429 stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
432 * Search is for a value that we do not know a priori, but we will
433 * assume it is not NULL. Estimate the selectivity as non-null
434 * fraction divided by number of distinct values, so that we get a
435 * result averaged over all possible values whether common or
436 * uncommon. (Essentially, we are assuming that the not-yet-known
437 * comparison value is equally likely to be any of the possible
438 * values, regardless of their frequency in the table. Is that a good
441 selec = 1.0 - stats->stanullfrac;
442 ndistinct = get_variable_numdistinct(vardata, &isdefault);
447 * Cross-check: selectivity should never be estimated as more than the
448 * most common value's.
450 if (get_attstatsslot(vardata->statsTuple,
451 vardata->atttype, vardata->atttypmod,
452 STATISTIC_KIND_MCV, InvalidOid,
455 &numbers, &nnumbers))
457 if (nnumbers > 0 && selec > numbers[0])
459 free_attstatsslot(vardata->atttype, NULL, 0, numbers, nnumbers);
465 * No ANALYZE stats available, so make a guess using estimated number
466 * of distinct values and assuming they are equally common. (The guess
467 * is unlikely to be very good, but we do know a few special cases.)
469 selec = 1.0 / get_variable_numdistinct(vardata, &isdefault);
472 /* result should be in range, but make sure... */
473 CLAMP_PROBABILITY(selec);
479 * neqsel - Selectivity of "!=" for any data types.
481 * This routine is also used for some operators that are not "!="
482 * but have comparable selectivity behavior. See above comments
486 neqsel(PG_FUNCTION_ARGS)
488 PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
489 Oid operator = PG_GETARG_OID(1);
490 List *args = (List *) PG_GETARG_POINTER(2);
491 int varRelid = PG_GETARG_INT32(3);
496 * We want 1 - eqsel() where the equality operator is the one associated
497 * with this != operator, that is, its negator.
499 eqop = get_negator(operator);
502 result = DatumGetFloat8(DirectFunctionCall4(eqsel,
503 PointerGetDatum(root),
504 ObjectIdGetDatum(eqop),
505 PointerGetDatum(args),
506 Int32GetDatum(varRelid)));
510 /* Use default selectivity (should we raise an error instead?) */
511 result = DEFAULT_EQ_SEL;
513 result = 1.0 - result;
514 PG_RETURN_FLOAT8(result);
518 * scalarineqsel - Selectivity of "<", "<=", ">", ">=" for scalars.
520 * This is the guts of both scalarltsel and scalargtsel. The caller has
521 * commuted the clause, if necessary, so that we can treat the variable as
522 * being on the left. The caller must also make sure that the other side
523 * of the clause is a non-null Const, and dissect same into a value and
526 * This routine works for any datatype (or pair of datatypes) known to
527 * convert_to_scalar(). If it is applied to some other datatype,
528 * it will return a default estimate.
531 scalarineqsel(PlannerInfo *root, Oid operator, bool isgt,
532 VariableStatData *vardata, Datum constval, Oid consttype)
534 Form_pg_statistic stats;
541 if (!HeapTupleIsValid(vardata->statsTuple))
543 /* no stats available, so default result */
544 return DEFAULT_INEQ_SEL;
546 stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
548 fmgr_info(get_opcode(operator), &opproc);
551 * If we have most-common-values info, add up the fractions of the MCV
552 * entries that satisfy MCV OP CONST. These fractions contribute directly
553 * to the result selectivity. Also add up the total fraction represented
556 mcv_selec = mcv_selectivity(vardata, &opproc, constval, true,
560 * If there is a histogram, determine which bin the constant falls in, and
561 * compute the resulting contribution to selectivity.
563 hist_selec = ineq_histogram_selectivity(root, vardata, &opproc, isgt,
564 constval, consttype);
567 * Now merge the results from the MCV and histogram calculations,
568 * realizing that the histogram covers only the non-null values that are
571 selec = 1.0 - stats->stanullfrac - sumcommon;
573 if (hist_selec >= 0.0)
578 * If no histogram but there are values not accounted for by MCV,
579 * arbitrarily assume half of them will match.
586 /* result should be in range, but make sure... */
587 CLAMP_PROBABILITY(selec);
593 * mcv_selectivity - Examine the MCV list for selectivity estimates
595 * Determine the fraction of the variable's MCV population that satisfies
596 * the predicate (VAR OP CONST), or (CONST OP VAR) if !varonleft. Also
597 * compute the fraction of the total column population represented by the MCV
598 * list. This code will work for any boolean-returning predicate operator.
600 * The function result is the MCV selectivity, and the fraction of the
601 * total population is returned into *sumcommonp. Zeroes are returned
602 * if there is no MCV list.
605 mcv_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
606 Datum constval, bool varonleft,
620 if (HeapTupleIsValid(vardata->statsTuple) &&
621 get_attstatsslot(vardata->statsTuple,
622 vardata->atttype, vardata->atttypmod,
623 STATISTIC_KIND_MCV, InvalidOid,
626 &numbers, &nnumbers))
628 for (i = 0; i < nvalues; i++)
631 DatumGetBool(FunctionCall2Coll(opproc,
632 DEFAULT_COLLATION_OID,
635 DatumGetBool(FunctionCall2Coll(opproc,
636 DEFAULT_COLLATION_OID,
639 mcv_selec += numbers[i];
640 sumcommon += numbers[i];
642 free_attstatsslot(vardata->atttype, values, nvalues,
646 *sumcommonp = sumcommon;
651 * histogram_selectivity - Examine the histogram for selectivity estimates
653 * Determine the fraction of the variable's histogram entries that satisfy
654 * the predicate (VAR OP CONST), or (CONST OP VAR) if !varonleft.
656 * This code will work for any boolean-returning predicate operator, whether
657 * or not it has anything to do with the histogram sort operator. We are
658 * essentially using the histogram just as a representative sample. However,
659 * small histograms are unlikely to be all that representative, so the caller
660 * should be prepared to fall back on some other estimation approach when the
661 * histogram is missing or very small. It may also be prudent to combine this
662 * approach with another one when the histogram is small.
664 * If the actual histogram size is not at least min_hist_size, we won't bother
665 * to do the calculation at all. Also, if the n_skip parameter is > 0, we
666 * ignore the first and last n_skip histogram elements, on the grounds that
667 * they are outliers and hence not very representative. Typical values for
668 * these parameters are 10 and 1.
670 * The function result is the selectivity, or -1 if there is no histogram
671 * or it's smaller than min_hist_size.
673 * The output parameter *hist_size receives the actual histogram size,
674 * or zero if no histogram. Callers may use this number to decide how
675 * much faith to put in the function result.
677 * Note that the result disregards both the most-common-values (if any) and
678 * null entries. The caller is expected to combine this result with
679 * statistics for those portions of the column population. It may also be
680 * prudent to clamp the result range, ie, disbelieve exact 0 or 1 outputs.
683 histogram_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
684 Datum constval, bool varonleft,
685 int min_hist_size, int n_skip,
692 /* check sanity of parameters */
694 Assert(min_hist_size > 2 * n_skip);
696 if (HeapTupleIsValid(vardata->statsTuple) &&
697 get_attstatsslot(vardata->statsTuple,
698 vardata->atttype, vardata->atttypmod,
699 STATISTIC_KIND_HISTOGRAM, InvalidOid,
704 *hist_size = nvalues;
705 if (nvalues >= min_hist_size)
710 for (i = n_skip; i < nvalues - n_skip; i++)
713 DatumGetBool(FunctionCall2Coll(opproc,
714 DEFAULT_COLLATION_OID,
717 DatumGetBool(FunctionCall2Coll(opproc,
718 DEFAULT_COLLATION_OID,
723 result = ((double) nmatch) / ((double) (nvalues - 2 * n_skip));
727 free_attstatsslot(vardata->atttype, values, nvalues, NULL, 0);
739 * ineq_histogram_selectivity - Examine the histogram for scalarineqsel
741 * Determine the fraction of the variable's histogram population that
742 * satisfies the inequality condition, ie, VAR < CONST or VAR > CONST.
744 * Returns -1 if there is no histogram (valid results will always be >= 0).
746 * Note that the result disregards both the most-common-values (if any) and
747 * null entries. The caller is expected to combine this result with
748 * statistics for those portions of the column population.
751 ineq_histogram_selectivity(PlannerInfo *root,
752 VariableStatData *vardata,
753 FmgrInfo *opproc, bool isgt,
754 Datum constval, Oid consttype)
764 * Someday, ANALYZE might store more than one histogram per rel/att,
765 * corresponding to more than one possible sort ordering defined for the
766 * column type. However, to make that work we will need to figure out
767 * which staop to search for --- it's not necessarily the one we have at
768 * hand! (For example, we might have a '<=' operator rather than the '<'
769 * operator that will appear in staop.) For now, assume that whatever
770 * appears in pg_statistic is sorted the same way our operator sorts, or
771 * the reverse way if isgt is TRUE.
773 if (HeapTupleIsValid(vardata->statsTuple) &&
774 get_attstatsslot(vardata->statsTuple,
775 vardata->atttype, vardata->atttypmod,
776 STATISTIC_KIND_HISTOGRAM, InvalidOid,
784 * Use binary search to find proper location, ie, the first slot
785 * at which the comparison fails. (If the given operator isn't
786 * actually sort-compatible with the histogram, you'll get garbage
787 * results ... but probably not any more garbage-y than you would
788 * from the old linear search.)
790 * If the binary search accesses the first or last histogram
791 * entry, we try to replace that endpoint with the true column min
792 * or max as found by get_actual_variable_range(). This
793 * ameliorates misestimates when the min or max is moving as a
794 * result of changes since the last ANALYZE. Note that this could
795 * result in effectively including MCVs into the histogram that
796 * weren't there before, but we don't try to correct for that.
799 int lobound = 0; /* first possible slot to search */
800 int hibound = nvalues; /* last+1 slot to search */
801 bool have_end = false;
804 * If there are only two histogram entries, we'll want up-to-date
805 * values for both. (If there are more than two, we need at most
806 * one of them to be updated, so we deal with that within the
810 have_end = get_actual_variable_range(root,
816 while (lobound < hibound)
818 int probe = (lobound + hibound) / 2;
822 * If we find ourselves about to compare to the first or last
823 * histogram entry, first try to replace it with the actual
824 * current min or max (unless we already did so above).
826 if (probe == 0 && nvalues > 2)
827 have_end = get_actual_variable_range(root,
832 else if (probe == nvalues - 1 && nvalues > 2)
833 have_end = get_actual_variable_range(root,
839 ltcmp = DatumGetBool(FunctionCall2Coll(opproc,
840 DEFAULT_COLLATION_OID,
853 /* Constant is below lower histogram boundary. */
856 else if (lobound >= nvalues)
858 /* Constant is above upper histogram boundary. */
870 * We have values[i-1] <= constant <= values[i].
872 * Convert the constant and the two nearest bin boundary
873 * values to a uniform comparison scale, and do a linear
874 * interpolation within this bin.
876 if (convert_to_scalar(constval, consttype, &val,
877 values[i - 1], values[i],
883 /* cope if bin boundaries appear identical */
888 else if (val >= high)
892 binfrac = (val - low) / (high - low);
895 * Watch out for the possibility that we got a NaN or
896 * Infinity from the division. This can happen
897 * despite the previous checks, if for example "low"
900 if (isnan(binfrac) ||
901 binfrac < 0.0 || binfrac > 1.0)
908 * Ideally we'd produce an error here, on the grounds that
909 * the given operator shouldn't have scalarXXsel
910 * registered as its selectivity func unless we can deal
911 * with its operand types. But currently, all manner of
912 * stuff is invoking scalarXXsel, so give a default
913 * estimate until that can be fixed.
919 * Now, compute the overall selectivity across the values
920 * represented by the histogram. We have i-1 full bins and
921 * binfrac partial bin below the constant.
923 histfrac = (double) (i - 1) + binfrac;
924 histfrac /= (double) (nvalues - 1);
928 * Now histfrac = fraction of histogram entries below the
931 * Account for "<" vs ">"
933 hist_selec = isgt ? (1.0 - histfrac) : histfrac;
936 * The histogram boundaries are only approximate to begin with,
937 * and may well be out of date anyway. Therefore, don't believe
938 * extremely small or large selectivity estimates --- unless we
939 * got actual current endpoint values from the table.
942 CLAMP_PROBABILITY(hist_selec);
945 if (hist_selec < 0.0001)
947 else if (hist_selec > 0.9999)
952 free_attstatsslot(vardata->atttype, values, nvalues, NULL, 0);
959 * scalarltsel - Selectivity of "<" (also "<=") for scalars.
962 scalarltsel(PG_FUNCTION_ARGS)
964 PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
965 Oid operator = PG_GETARG_OID(1);
966 List *args = (List *) PG_GETARG_POINTER(2);
967 int varRelid = PG_GETARG_INT32(3);
968 VariableStatData vardata;
977 * If expression is not variable op something or something op variable,
978 * then punt and return a default estimate.
980 if (!get_restriction_variable(root, args, varRelid,
981 &vardata, &other, &varonleft))
982 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
985 * Can't do anything useful if the something is not a constant, either.
987 if (!IsA(other, Const))
989 ReleaseVariableStats(vardata);
990 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
994 * If the constant is NULL, assume operator is strict and return zero, ie,
995 * operator will never return TRUE.
997 if (((Const *) other)->constisnull)
999 ReleaseVariableStats(vardata);
1000 PG_RETURN_FLOAT8(0.0);
1002 constval = ((Const *) other)->constvalue;
1003 consttype = ((Const *) other)->consttype;
1006 * Force the var to be on the left to simplify logic in scalarineqsel.
1010 /* we have var < other */
1015 /* we have other < var, commute to make var > other */
1016 operator = get_commutator(operator);
1019 /* Use default selectivity (should we raise an error instead?) */
1020 ReleaseVariableStats(vardata);
1021 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
1026 selec = scalarineqsel(root, operator, isgt, &vardata, constval, consttype);
1028 ReleaseVariableStats(vardata);
1030 PG_RETURN_FLOAT8((float8) selec);
1034 * scalargtsel - Selectivity of ">" (also ">=") for integers.
1037 scalargtsel(PG_FUNCTION_ARGS)
1039 PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
1040 Oid operator = PG_GETARG_OID(1);
1041 List *args = (List *) PG_GETARG_POINTER(2);
1042 int varRelid = PG_GETARG_INT32(3);
1043 VariableStatData vardata;
1052 * If expression is not variable op something or something op variable,
1053 * then punt and return a default estimate.
1055 if (!get_restriction_variable(root, args, varRelid,
1056 &vardata, &other, &varonleft))
1057 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
1060 * Can't do anything useful if the something is not a constant, either.
1062 if (!IsA(other, Const))
1064 ReleaseVariableStats(vardata);
1065 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
1069 * If the constant is NULL, assume operator is strict and return zero, ie,
1070 * operator will never return TRUE.
1072 if (((Const *) other)->constisnull)
1074 ReleaseVariableStats(vardata);
1075 PG_RETURN_FLOAT8(0.0);
1077 constval = ((Const *) other)->constvalue;
1078 consttype = ((Const *) other)->consttype;
1081 * Force the var to be on the left to simplify logic in scalarineqsel.
1085 /* we have var > other */
1090 /* we have other > var, commute to make var < other */
1091 operator = get_commutator(operator);
1094 /* Use default selectivity (should we raise an error instead?) */
1095 ReleaseVariableStats(vardata);
1096 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
1101 selec = scalarineqsel(root, operator, isgt, &vardata, constval, consttype);
1103 ReleaseVariableStats(vardata);
1105 PG_RETURN_FLOAT8((float8) selec);
1109 * patternsel - Generic code for pattern-match selectivity.
1112 patternsel(PG_FUNCTION_ARGS, Pattern_Type ptype, bool negate)
1114 PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
1115 Oid operator = PG_GETARG_OID(1);
1116 List *args = (List *) PG_GETARG_POINTER(2);
1117 int varRelid = PG_GETARG_INT32(3);
1118 Oid collation = PG_GET_COLLATION();
1119 VariableStatData vardata;
1126 Pattern_Prefix_Status pstatus;
1128 Const *prefix = NULL;
1129 Selectivity rest_selec = 0;
1133 * If this is for a NOT LIKE or similar operator, get the corresponding
1134 * positive-match operator and work with that. Set result to the correct
1135 * default estimate, too.
1139 operator = get_negator(operator);
1140 if (!OidIsValid(operator))
1141 elog(ERROR, "patternsel called for operator without a negator");
1142 result = 1.0 - DEFAULT_MATCH_SEL;
1146 result = DEFAULT_MATCH_SEL;
1150 * If expression is not variable op constant, then punt and return a
1153 if (!get_restriction_variable(root, args, varRelid,
1154 &vardata, &other, &varonleft))
1156 if (!varonleft || !IsA(other, Const))
1158 ReleaseVariableStats(vardata);
1163 * If the constant is NULL, assume operator is strict and return zero, ie,
1164 * operator will never return TRUE. (It's zero even for a negator op.)
1166 if (((Const *) other)->constisnull)
1168 ReleaseVariableStats(vardata);
1171 constval = ((Const *) other)->constvalue;
1172 consttype = ((Const *) other)->consttype;
1175 * The right-hand const is type text or bytea for all supported operators.
1176 * We do not expect to see binary-compatible types here, since
1177 * const-folding should have relabeled the const to exactly match the
1178 * operator's declared type.
1180 if (consttype != TEXTOID && consttype != BYTEAOID)
1182 ReleaseVariableStats(vardata);
1187 * Similarly, the exposed type of the left-hand side should be one of
1188 * those we know. (Do not look at vardata.atttype, which might be
1189 * something binary-compatible but different.) We can use it to choose
1190 * the index opfamily from which we must draw the comparison operators.
1192 * NOTE: It would be more correct to use the PATTERN opfamilies than the
1193 * simple ones, but at the moment ANALYZE will not generate statistics for
1194 * the PATTERN operators. But our results are so approximate anyway that
1195 * it probably hardly matters.
1197 vartype = vardata.vartype;
1202 opfamily = TEXT_BTREE_FAM_OID;
1205 opfamily = BPCHAR_BTREE_FAM_OID;
1208 opfamily = NAME_BTREE_FAM_OID;
1211 opfamily = BYTEA_BTREE_FAM_OID;
1214 ReleaseVariableStats(vardata);
1219 * Pull out any fixed prefix implied by the pattern, and estimate the
1220 * fractional selectivity of the remainder of the pattern. Unlike many of
1221 * the other functions in this file, we use the pattern operator's actual
1222 * collation for this step. This is not because we expect the collation
1223 * to make a big difference in the selectivity estimate (it seldom would),
1224 * but because we want to be sure we cache compiled regexps under the
1225 * right cache key, so that they can be re-used at runtime.
1227 patt = (Const *) other;
1228 pstatus = pattern_fixed_prefix(patt, ptype, collation,
1229 &prefix, &rest_selec);
1232 * If necessary, coerce the prefix constant to the right type.
1234 if (prefix && prefix->consttype != vartype)
1238 switch (prefix->consttype)
1241 prefixstr = TextDatumGetCString(prefix->constvalue);
1244 prefixstr = DatumGetCString(DirectFunctionCall1(byteaout,
1245 prefix->constvalue));
1248 elog(ERROR, "unrecognized consttype: %u",
1250 ReleaseVariableStats(vardata);
1253 prefix = string_to_const(prefixstr, vartype);
1257 if (pstatus == Pattern_Prefix_Exact)
1260 * Pattern specifies an exact match, so pretend operator is '='
1262 Oid eqopr = get_opfamily_member(opfamily, vartype, vartype,
1263 BTEqualStrategyNumber);
1265 if (eqopr == InvalidOid)
1266 elog(ERROR, "no = operator for opfamily %u", opfamily);
1267 result = var_eq_const(&vardata, eqopr, prefix->constvalue,
1273 * Not exact-match pattern. If we have a sufficiently large
1274 * histogram, estimate selectivity for the histogram part of the
1275 * population by counting matches in the histogram. If not, estimate
1276 * selectivity of the fixed prefix and remainder of pattern
1277 * separately, then combine the two to get an estimate of the
1278 * selectivity for the part of the column population represented by
1279 * the histogram. (For small histograms, we combine these
1282 * We then add up data for any most-common-values values; these are
1283 * not in the histogram population, and we can get exact answers for
1284 * them by applying the pattern operator, so there's no reason to
1285 * approximate. (If the MCVs cover a significant part of the total
1286 * population, this gives us a big leg up in accuracy.)
1295 /* Try to use the histogram entries to get selectivity */
1296 fmgr_info(get_opcode(operator), &opproc);
1298 selec = histogram_selectivity(&vardata, &opproc, constval, true,
1301 /* If not at least 100 entries, use the heuristic method */
1302 if (hist_size < 100)
1304 Selectivity heursel;
1305 Selectivity prefixsel;
1307 if (pstatus == Pattern_Prefix_Partial)
1308 prefixsel = prefix_selectivity(root, &vardata, vartype,
1312 heursel = prefixsel * rest_selec;
1314 if (selec < 0) /* fewer than 10 histogram entries? */
1319 * For histogram sizes from 10 to 100, we combine the
1320 * histogram and heuristic selectivities, putting increasingly
1321 * more trust in the histogram for larger sizes.
1323 double hist_weight = hist_size / 100.0;
1325 selec = selec * hist_weight + heursel * (1.0 - hist_weight);
1329 /* In any case, don't believe extremely small or large estimates. */
1332 else if (selec > 0.9999)
1336 * If we have most-common-values info, add up the fractions of the MCV
1337 * entries that satisfy MCV OP PATTERN. These fractions contribute
1338 * directly to the result selectivity. Also add up the total fraction
1339 * represented by MCV entries.
1341 mcv_selec = mcv_selectivity(&vardata, &opproc, constval, true,
1344 if (HeapTupleIsValid(vardata.statsTuple))
1345 nullfrac = ((Form_pg_statistic) GETSTRUCT(vardata.statsTuple))->stanullfrac;
1350 * Now merge the results from the MCV and histogram calculations,
1351 * realizing that the histogram covers only the non-null values that
1352 * are not listed in MCV.
1354 selec *= 1.0 - nullfrac - sumcommon;
1357 /* result should be in range, but make sure... */
1358 CLAMP_PROBABILITY(selec);
1364 pfree(DatumGetPointer(prefix->constvalue));
1368 ReleaseVariableStats(vardata);
1370 return negate ? (1.0 - result) : result;
1374 * regexeqsel - Selectivity of regular-expression pattern match.
1377 regexeqsel(PG_FUNCTION_ARGS)
1379 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Regex, false));
1383 * icregexeqsel - Selectivity of case-insensitive regex match.
1386 icregexeqsel(PG_FUNCTION_ARGS)
1388 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Regex_IC, false));
1392 * likesel - Selectivity of LIKE pattern match.
1395 likesel(PG_FUNCTION_ARGS)
1397 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Like, false));
1401 * iclikesel - Selectivity of ILIKE pattern match.
1404 iclikesel(PG_FUNCTION_ARGS)
1406 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Like_IC, false));
1410 * regexnesel - Selectivity of regular-expression pattern non-match.
1413 regexnesel(PG_FUNCTION_ARGS)
1415 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Regex, true));
1419 * icregexnesel - Selectivity of case-insensitive regex non-match.
1422 icregexnesel(PG_FUNCTION_ARGS)
1424 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Regex_IC, true));
1428 * nlikesel - Selectivity of LIKE pattern non-match.
1431 nlikesel(PG_FUNCTION_ARGS)
1433 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Like, true));
1437 * icnlikesel - Selectivity of ILIKE pattern non-match.
1440 icnlikesel(PG_FUNCTION_ARGS)
1442 PG_RETURN_FLOAT8(patternsel(fcinfo, Pattern_Type_Like_IC, true));
1446 * boolvarsel - Selectivity of Boolean variable.
1448 * This can actually be called on any boolean-valued expression. If it
1449 * involves only Vars of the specified relation, and if there are statistics
1450 * about the Var or expression (the latter is possible if it's indexed) then
1451 * we'll produce a real estimate; otherwise it's just a default.
1454 boolvarsel(PlannerInfo *root, Node *arg, int varRelid)
1456 VariableStatData vardata;
1459 examine_variable(root, arg, varRelid, &vardata);
1460 if (HeapTupleIsValid(vardata.statsTuple))
1463 * A boolean variable V is equivalent to the clause V = 't', so we
1464 * compute the selectivity as if that is what we have.
1466 selec = var_eq_const(&vardata, BooleanEqualOperator,
1467 BoolGetDatum(true), false, true);
1469 else if (is_funcclause(arg))
1472 * If we have no stats and it's a function call, estimate 0.3333333.
1473 * This seems a pretty unprincipled choice, but Postgres has been
1474 * using that estimate for function calls since 1992. The hoariness
1475 * of this behavior suggests that we should not be in too much hurry
1476 * to use another value.
1482 /* Otherwise, the default estimate is 0.5 */
1485 ReleaseVariableStats(vardata);
1490 * booltestsel - Selectivity of BooleanTest Node.
1493 booltestsel(PlannerInfo *root, BoolTestType booltesttype, Node *arg,
1494 int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo)
1496 VariableStatData vardata;
1499 examine_variable(root, arg, varRelid, &vardata);
1501 if (HeapTupleIsValid(vardata.statsTuple))
1503 Form_pg_statistic stats;
1510 stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
1511 freq_null = stats->stanullfrac;
1513 if (get_attstatsslot(vardata.statsTuple,
1514 vardata.atttype, vardata.atttypmod,
1515 STATISTIC_KIND_MCV, InvalidOid,
1518 &numbers, &nnumbers)
1525 * Get first MCV frequency and derive frequency for true.
1527 if (DatumGetBool(values[0]))
1528 freq_true = numbers[0];
1530 freq_true = 1.0 - numbers[0] - freq_null;
1533 * Next derive frequency for false. Then use these as appropriate
1534 * to derive frequency for each case.
1536 freq_false = 1.0 - freq_true - freq_null;
1538 switch (booltesttype)
1541 /* select only NULL values */
1544 case IS_NOT_UNKNOWN:
1545 /* select non-NULL values */
1546 selec = 1.0 - freq_null;
1549 /* select only TRUE values */
1553 /* select non-TRUE values */
1554 selec = 1.0 - freq_true;
1557 /* select only FALSE values */
1561 /* select non-FALSE values */
1562 selec = 1.0 - freq_false;
1565 elog(ERROR, "unrecognized booltesttype: %d",
1566 (int) booltesttype);
1567 selec = 0.0; /* Keep compiler quiet */
1571 free_attstatsslot(vardata.atttype, values, nvalues,
1577 * No most-common-value info available. Still have null fraction
1578 * information, so use it for IS [NOT] UNKNOWN. Otherwise adjust
1579 * for null fraction and assume a 50-50 split of TRUE and FALSE.
1581 switch (booltesttype)
1584 /* select only NULL values */
1587 case IS_NOT_UNKNOWN:
1588 /* select non-NULL values */
1589 selec = 1.0 - freq_null;
1593 /* Assume we select half of the non-NULL values */
1594 selec = (1.0 - freq_null) / 2.0;
1598 /* Assume we select NULLs plus half of the non-NULLs */
1599 /* equiv. to freq_null + (1.0 - freq_null) / 2.0 */
1600 selec = (freq_null + 1.0) / 2.0;
1603 elog(ERROR, "unrecognized booltesttype: %d",
1604 (int) booltesttype);
1605 selec = 0.0; /* Keep compiler quiet */
1613 * If we can't get variable statistics for the argument, perhaps
1614 * clause_selectivity can do something with it. We ignore the
1615 * possibility of a NULL value when using clause_selectivity, and just
1616 * assume the value is either TRUE or FALSE.
1618 switch (booltesttype)
1621 selec = DEFAULT_UNK_SEL;
1623 case IS_NOT_UNKNOWN:
1624 selec = DEFAULT_NOT_UNK_SEL;
1628 selec = (double) clause_selectivity(root, arg,
1634 selec = 1.0 - (double) clause_selectivity(root, arg,
1639 elog(ERROR, "unrecognized booltesttype: %d",
1640 (int) booltesttype);
1641 selec = 0.0; /* Keep compiler quiet */
1646 ReleaseVariableStats(vardata);
1648 /* result should be in range, but make sure... */
1649 CLAMP_PROBABILITY(selec);
1651 return (Selectivity) selec;
1655 * nulltestsel - Selectivity of NullTest Node.
1658 nulltestsel(PlannerInfo *root, NullTestType nulltesttype, Node *arg,
1659 int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo)
1661 VariableStatData vardata;
1664 examine_variable(root, arg, varRelid, &vardata);
1666 if (HeapTupleIsValid(vardata.statsTuple))
1668 Form_pg_statistic stats;
1671 stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
1672 freq_null = stats->stanullfrac;
1674 switch (nulltesttype)
1679 * Use freq_null directly.
1686 * Select not unknown (not null) values. Calculate from
1689 selec = 1.0 - freq_null;
1692 elog(ERROR, "unrecognized nulltesttype: %d",
1693 (int) nulltesttype);
1694 return (Selectivity) 0; /* keep compiler quiet */
1700 * No ANALYZE stats available, so make a guess
1702 switch (nulltesttype)
1705 selec = DEFAULT_UNK_SEL;
1708 selec = DEFAULT_NOT_UNK_SEL;
1711 elog(ERROR, "unrecognized nulltesttype: %d",
1712 (int) nulltesttype);
1713 return (Selectivity) 0; /* keep compiler quiet */
1717 ReleaseVariableStats(vardata);
1719 /* result should be in range, but make sure... */
1720 CLAMP_PROBABILITY(selec);
1722 return (Selectivity) selec;
1726 * strip_array_coercion - strip binary-compatible relabeling from an array expr
1728 * For array values, the parser normally generates ArrayCoerceExpr conversions,
1729 * but it seems possible that RelabelType might show up. Also, the planner
1730 * is not currently tense about collapsing stacked ArrayCoerceExpr nodes,
1731 * so we need to be ready to deal with more than one level.
1734 strip_array_coercion(Node *node)
1738 if (node && IsA(node, ArrayCoerceExpr) &&
1739 ((ArrayCoerceExpr *) node)->elemfuncid == InvalidOid)
1741 node = (Node *) ((ArrayCoerceExpr *) node)->arg;
1743 else if (node && IsA(node, RelabelType))
1745 /* We don't really expect this case, but may as well cope */
1746 node = (Node *) ((RelabelType *) node)->arg;
1755 * scalararraysel - Selectivity of ScalarArrayOpExpr Node.
1758 scalararraysel(PlannerInfo *root,
1759 ScalarArrayOpExpr *clause,
1760 bool is_join_clause,
1763 SpecialJoinInfo *sjinfo)
1765 Oid operator = clause->opno;
1766 bool useOr = clause->useOr;
1767 bool isEquality = false;
1768 bool isInequality = false;
1771 Oid nominal_element_type;
1772 Oid nominal_element_collation;
1773 TypeCacheEntry *typentry;
1774 RegProcedure oprsel;
1775 FmgrInfo oprselproc;
1777 Selectivity s1disjoint;
1779 /* First, deconstruct the expression */
1780 Assert(list_length(clause->args) == 2);
1781 leftop = (Node *) linitial(clause->args);
1782 rightop = (Node *) lsecond(clause->args);
1784 /* aggressively reduce both sides to constants */
1785 leftop = estimate_expression_value(root, leftop);
1786 rightop = estimate_expression_value(root, rightop);
1788 /* get nominal (after relabeling) element type of rightop */
1789 nominal_element_type = get_base_element_type(exprType(rightop));
1790 if (!OidIsValid(nominal_element_type))
1791 return (Selectivity) 0.5; /* probably shouldn't happen */
1792 /* get nominal collation, too, for generating constants */
1793 nominal_element_collation = exprCollation(rightop);
1795 /* look through any binary-compatible relabeling of rightop */
1796 rightop = strip_array_coercion(rightop);
1799 * Detect whether the operator is the default equality or inequality
1800 * operator of the array element type.
1802 typentry = lookup_type_cache(nominal_element_type, TYPECACHE_EQ_OPR);
1803 if (OidIsValid(typentry->eq_opr))
1805 if (operator == typentry->eq_opr)
1807 else if (get_negator(operator) == typentry->eq_opr)
1808 isInequality = true;
1812 * If it is equality or inequality, we might be able to estimate this as a
1813 * form of array containment; for instance "const = ANY(column)" can be
1814 * treated as "ARRAY[const] <@ column". scalararraysel_containment tries
1815 * that, and returns the selectivity estimate if successful, or -1 if not.
1817 if ((isEquality || isInequality) && !is_join_clause)
1819 s1 = scalararraysel_containment(root, leftop, rightop,
1820 nominal_element_type,
1821 isEquality, useOr, varRelid);
1827 * Look up the underlying operator's selectivity estimator. Punt if it
1831 oprsel = get_oprjoin(operator);
1833 oprsel = get_oprrest(operator);
1835 return (Selectivity) 0.5;
1836 fmgr_info(oprsel, &oprselproc);
1839 * In the array-containment check above, we must only believe that an
1840 * operator is equality or inequality if it is the default btree equality
1841 * operator (or its negator) for the element type, since those are the
1842 * operators that array containment will use. But in what follows, we can
1843 * be a little laxer, and also believe that any operators using eqsel() or
1844 * neqsel() as selectivity estimator act like equality or inequality.
1846 if (oprsel == F_EQSEL || oprsel == F_EQJOINSEL)
1848 else if (oprsel == F_NEQSEL || oprsel == F_NEQJOINSEL)
1849 isInequality = true;
1852 * We consider three cases:
1854 * 1. rightop is an Array constant: deconstruct the array, apply the
1855 * operator's selectivity function for each array element, and merge the
1856 * results in the same way that clausesel.c does for AND/OR combinations.
1858 * 2. rightop is an ARRAY[] construct: apply the operator's selectivity
1859 * function for each element of the ARRAY[] construct, and merge.
1861 * 3. otherwise, make a guess ...
1863 if (rightop && IsA(rightop, Const))
1865 Datum arraydatum = ((Const *) rightop)->constvalue;
1866 bool arrayisnull = ((Const *) rightop)->constisnull;
1867 ArrayType *arrayval;
1876 if (arrayisnull) /* qual can't succeed if null array */
1877 return (Selectivity) 0.0;
1878 arrayval = DatumGetArrayTypeP(arraydatum);
1879 get_typlenbyvalalign(ARR_ELEMTYPE(arrayval),
1880 &elmlen, &elmbyval, &elmalign);
1881 deconstruct_array(arrayval,
1882 ARR_ELEMTYPE(arrayval),
1883 elmlen, elmbyval, elmalign,
1884 &elem_values, &elem_nulls, &num_elems);
1887 * For generic operators, we assume the probability of success is
1888 * independent for each array element. But for "= ANY" or "<> ALL",
1889 * if the array elements are distinct (which'd typically be the case)
1890 * then the probabilities are disjoint, and we should just sum them.
1892 * If we were being really tense we would try to confirm that the
1893 * elements are all distinct, but that would be expensive and it
1894 * doesn't seem to be worth the cycles; it would amount to penalizing
1895 * well-written queries in favor of poorly-written ones. However, we
1896 * do protect ourselves a little bit by checking whether the
1897 * disjointness assumption leads to an impossible (out of range)
1898 * probability; if so, we fall back to the normal calculation.
1900 s1 = s1disjoint = (useOr ? 0.0 : 1.0);
1902 for (i = 0; i < num_elems; i++)
1907 args = list_make2(leftop,
1908 makeConst(nominal_element_type,
1910 nominal_element_collation,
1916 s2 = DatumGetFloat8(FunctionCall5Coll(&oprselproc,
1917 clause->inputcollid,
1918 PointerGetDatum(root),
1919 ObjectIdGetDatum(operator),
1920 PointerGetDatum(args),
1921 Int16GetDatum(jointype),
1922 PointerGetDatum(sjinfo)));
1924 s2 = DatumGetFloat8(FunctionCall4Coll(&oprselproc,
1925 clause->inputcollid,
1926 PointerGetDatum(root),
1927 ObjectIdGetDatum(operator),
1928 PointerGetDatum(args),
1929 Int32GetDatum(varRelid)));
1933 s1 = s1 + s2 - s1 * s2;
1941 s1disjoint += s2 - 1.0;
1945 /* accept disjoint-probability estimate if in range */
1946 if ((useOr ? isEquality : isInequality) &&
1947 s1disjoint >= 0.0 && s1disjoint <= 1.0)
1950 else if (rightop && IsA(rightop, ArrayExpr) &&
1951 !((ArrayExpr *) rightop)->multidims)
1953 ArrayExpr *arrayexpr = (ArrayExpr *) rightop;
1958 get_typlenbyval(arrayexpr->element_typeid,
1959 &elmlen, &elmbyval);
1962 * We use the assumption of disjoint probabilities here too, although
1963 * the odds of equal array elements are rather higher if the elements
1964 * are not all constants (which they won't be, else constant folding
1965 * would have reduced the ArrayExpr to a Const). In this path it's
1966 * critical to have the sanity check on the s1disjoint estimate.
1968 s1 = s1disjoint = (useOr ? 0.0 : 1.0);
1970 foreach(l, arrayexpr->elements)
1972 Node *elem = (Node *) lfirst(l);
1977 * Theoretically, if elem isn't of nominal_element_type we should
1978 * insert a RelabelType, but it seems unlikely that any operator
1979 * estimation function would really care ...
1981 args = list_make2(leftop, elem);
1983 s2 = DatumGetFloat8(FunctionCall5Coll(&oprselproc,
1984 clause->inputcollid,
1985 PointerGetDatum(root),
1986 ObjectIdGetDatum(operator),
1987 PointerGetDatum(args),
1988 Int16GetDatum(jointype),
1989 PointerGetDatum(sjinfo)));
1991 s2 = DatumGetFloat8(FunctionCall4Coll(&oprselproc,
1992 clause->inputcollid,
1993 PointerGetDatum(root),
1994 ObjectIdGetDatum(operator),
1995 PointerGetDatum(args),
1996 Int32GetDatum(varRelid)));
2000 s1 = s1 + s2 - s1 * s2;
2008 s1disjoint += s2 - 1.0;
2012 /* accept disjoint-probability estimate if in range */
2013 if ((useOr ? isEquality : isInequality) &&
2014 s1disjoint >= 0.0 && s1disjoint <= 1.0)
2019 CaseTestExpr *dummyexpr;
2025 * We need a dummy rightop to pass to the operator selectivity
2026 * routine. It can be pretty much anything that doesn't look like a
2027 * constant; CaseTestExpr is a convenient choice.
2029 dummyexpr = makeNode(CaseTestExpr);
2030 dummyexpr->typeId = nominal_element_type;
2031 dummyexpr->typeMod = -1;
2032 dummyexpr->collation = clause->inputcollid;
2033 args = list_make2(leftop, dummyexpr);
2035 s2 = DatumGetFloat8(FunctionCall5Coll(&oprselproc,
2036 clause->inputcollid,
2037 PointerGetDatum(root),
2038 ObjectIdGetDatum(operator),
2039 PointerGetDatum(args),
2040 Int16GetDatum(jointype),
2041 PointerGetDatum(sjinfo)));
2043 s2 = DatumGetFloat8(FunctionCall4Coll(&oprselproc,
2044 clause->inputcollid,
2045 PointerGetDatum(root),
2046 ObjectIdGetDatum(operator),
2047 PointerGetDatum(args),
2048 Int32GetDatum(varRelid)));
2049 s1 = useOr ? 0.0 : 1.0;
2052 * Arbitrarily assume 10 elements in the eventual array value (see
2053 * also estimate_array_length). We don't risk an assumption of
2054 * disjoint probabilities here.
2056 for (i = 0; i < 10; i++)
2059 s1 = s1 + s2 - s1 * s2;
2065 /* result should be in range, but make sure... */
2066 CLAMP_PROBABILITY(s1);
2072 * Estimate number of elements in the array yielded by an expression.
2074 * It's important that this agree with scalararraysel.
2077 estimate_array_length(Node *arrayexpr)
2079 /* look through any binary-compatible relabeling of arrayexpr */
2080 arrayexpr = strip_array_coercion(arrayexpr);
2082 if (arrayexpr && IsA(arrayexpr, Const))
2084 Datum arraydatum = ((Const *) arrayexpr)->constvalue;
2085 bool arrayisnull = ((Const *) arrayexpr)->constisnull;
2086 ArrayType *arrayval;
2090 arrayval = DatumGetArrayTypeP(arraydatum);
2091 return ArrayGetNItems(ARR_NDIM(arrayval), ARR_DIMS(arrayval));
2093 else if (arrayexpr && IsA(arrayexpr, ArrayExpr) &&
2094 !((ArrayExpr *) arrayexpr)->multidims)
2096 return list_length(((ArrayExpr *) arrayexpr)->elements);
2100 /* default guess --- see also scalararraysel */
2106 * rowcomparesel - Selectivity of RowCompareExpr Node.
2108 * We estimate RowCompare selectivity by considering just the first (high
2109 * order) columns, which makes it equivalent to an ordinary OpExpr. While
2110 * this estimate could be refined by considering additional columns, it
2111 * seems unlikely that we could do a lot better without multi-column
2115 rowcomparesel(PlannerInfo *root,
2116 RowCompareExpr *clause,
2117 int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo)
2120 Oid opno = linitial_oid(clause->opnos);
2121 Oid inputcollid = linitial_oid(clause->inputcollids);
2123 bool is_join_clause;
2125 /* Build equivalent arg list for single operator */
2126 opargs = list_make2(linitial(clause->largs), linitial(clause->rargs));
2129 * Decide if it's a join clause. This should match clausesel.c's
2130 * treat_as_join_clause(), except that we intentionally consider only the
2131 * leading columns and not the rest of the clause.
2136 * Caller is forcing restriction mode (eg, because we are examining an
2137 * inner indexscan qual).
2139 is_join_clause = false;
2141 else if (sjinfo == NULL)
2144 * It must be a restriction clause, since it's being evaluated at a
2147 is_join_clause = false;
2152 * Otherwise, it's a join if there's more than one relation used.
2154 is_join_clause = (NumRelids((Node *) opargs) > 1);
2159 /* Estimate selectivity for a join clause. */
2160 s1 = join_selectivity(root, opno,
2168 /* Estimate selectivity for a restriction clause. */
2169 s1 = restriction_selectivity(root, opno,
2179 * eqjoinsel - Join selectivity of "="
2182 eqjoinsel(PG_FUNCTION_ARGS)
2184 PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
2185 Oid operator = PG_GETARG_OID(1);
2186 List *args = (List *) PG_GETARG_POINTER(2);
2189 JoinType jointype = (JoinType) PG_GETARG_INT16(3);
2191 SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) PG_GETARG_POINTER(4);
2193 VariableStatData vardata1;
2194 VariableStatData vardata2;
2195 bool join_is_reversed;
2196 RelOptInfo *inner_rel;
2198 get_join_variables(root, args, sjinfo,
2199 &vardata1, &vardata2, &join_is_reversed);
2201 switch (sjinfo->jointype)
2206 selec = eqjoinsel_inner(operator, &vardata1, &vardata2);
2212 * Look up the join's inner relation. min_righthand is sufficient
2213 * information because neither SEMI nor ANTI joins permit any
2214 * reassociation into or out of their RHS, so the righthand will
2215 * always be exactly that set of rels.
2217 inner_rel = find_join_input_rel(root, sjinfo->min_righthand);
2219 if (!join_is_reversed)
2220 selec = eqjoinsel_semi(operator, &vardata1, &vardata2,
2223 selec = eqjoinsel_semi(get_commutator(operator),
2224 &vardata2, &vardata1,
2228 /* other values not expected here */
2229 elog(ERROR, "unrecognized join type: %d",
2230 (int) sjinfo->jointype);
2231 selec = 0; /* keep compiler quiet */
2235 ReleaseVariableStats(vardata1);
2236 ReleaseVariableStats(vardata2);
2238 CLAMP_PROBABILITY(selec);
2240 PG_RETURN_FLOAT8((float8) selec);
2244 * eqjoinsel_inner --- eqjoinsel for normal inner join
2246 * We also use this for LEFT/FULL outer joins; it's not presently clear
2247 * that it's worth trying to distinguish them here.
2250 eqjoinsel_inner(Oid operator,
2251 VariableStatData *vardata1, VariableStatData *vardata2)
2258 Form_pg_statistic stats1 = NULL;
2259 Form_pg_statistic stats2 = NULL;
2260 bool have_mcvs1 = false;
2261 Datum *values1 = NULL;
2263 float4 *numbers1 = NULL;
2265 bool have_mcvs2 = false;
2266 Datum *values2 = NULL;
2268 float4 *numbers2 = NULL;
2271 nd1 = get_variable_numdistinct(vardata1, &isdefault1);
2272 nd2 = get_variable_numdistinct(vardata2, &isdefault2);
2274 if (HeapTupleIsValid(vardata1->statsTuple))
2276 stats1 = (Form_pg_statistic) GETSTRUCT(vardata1->statsTuple);
2277 have_mcvs1 = get_attstatsslot(vardata1->statsTuple,
2279 vardata1->atttypmod,
2283 &values1, &nvalues1,
2284 &numbers1, &nnumbers1);
2287 if (HeapTupleIsValid(vardata2->statsTuple))
2289 stats2 = (Form_pg_statistic) GETSTRUCT(vardata2->statsTuple);
2290 have_mcvs2 = get_attstatsslot(vardata2->statsTuple,
2292 vardata2->atttypmod,
2296 &values2, &nvalues2,
2297 &numbers2, &nnumbers2);
2300 if (have_mcvs1 && have_mcvs2)
2303 * We have most-common-value lists for both relations. Run through
2304 * the lists to see which MCVs actually join to each other with the
2305 * given operator. This allows us to determine the exact join
2306 * selectivity for the portion of the relations represented by the MCV
2307 * lists. We still have to estimate for the remaining population, but
2308 * in a skewed distribution this gives us a big leg up in accuracy.
2309 * For motivation see the analysis in Y. Ioannidis and S.
2310 * Christodoulakis, "On the propagation of errors in the size of join
2311 * results", Technical Report 1018, Computer Science Dept., University
2312 * of Wisconsin, Madison, March 1991 (available from ftp.cs.wisc.edu).
2317 double nullfrac1 = stats1->stanullfrac;
2318 double nullfrac2 = stats2->stanullfrac;
2319 double matchprodfreq,
2331 fmgr_info(get_opcode(operator), &eqproc);
2332 hasmatch1 = (bool *) palloc0(nvalues1 * sizeof(bool));
2333 hasmatch2 = (bool *) palloc0(nvalues2 * sizeof(bool));
2336 * Note we assume that each MCV will match at most one member of the
2337 * other MCV list. If the operator isn't really equality, there could
2338 * be multiple matches --- but we don't look for them, both for speed
2339 * and because the math wouldn't add up...
2341 matchprodfreq = 0.0;
2343 for (i = 0; i < nvalues1; i++)
2347 for (j = 0; j < nvalues2; j++)
2351 if (DatumGetBool(FunctionCall2Coll(&eqproc,
2352 DEFAULT_COLLATION_OID,
2356 hasmatch1[i] = hasmatch2[j] = true;
2357 matchprodfreq += numbers1[i] * numbers2[j];
2363 CLAMP_PROBABILITY(matchprodfreq);
2364 /* Sum up frequencies of matched and unmatched MCVs */
2365 matchfreq1 = unmatchfreq1 = 0.0;
2366 for (i = 0; i < nvalues1; i++)
2369 matchfreq1 += numbers1[i];
2371 unmatchfreq1 += numbers1[i];
2373 CLAMP_PROBABILITY(matchfreq1);
2374 CLAMP_PROBABILITY(unmatchfreq1);
2375 matchfreq2 = unmatchfreq2 = 0.0;
2376 for (i = 0; i < nvalues2; i++)
2379 matchfreq2 += numbers2[i];
2381 unmatchfreq2 += numbers2[i];
2383 CLAMP_PROBABILITY(matchfreq2);
2384 CLAMP_PROBABILITY(unmatchfreq2);
2389 * Compute total frequency of non-null values that are not in the MCV
2392 otherfreq1 = 1.0 - nullfrac1 - matchfreq1 - unmatchfreq1;
2393 otherfreq2 = 1.0 - nullfrac2 - matchfreq2 - unmatchfreq2;
2394 CLAMP_PROBABILITY(otherfreq1);
2395 CLAMP_PROBABILITY(otherfreq2);
2398 * We can estimate the total selectivity from the point of view of
2399 * relation 1 as: the known selectivity for matched MCVs, plus
2400 * unmatched MCVs that are assumed to match against random members of
2401 * relation 2's non-MCV population, plus non-MCV values that are
2402 * assumed to match against random members of relation 2's unmatched
2403 * MCVs plus non-MCV values.
2405 totalsel1 = matchprodfreq;
2407 totalsel1 += unmatchfreq1 * otherfreq2 / (nd2 - nvalues2);
2409 totalsel1 += otherfreq1 * (otherfreq2 + unmatchfreq2) /
2411 /* Same estimate from the point of view of relation 2. */
2412 totalsel2 = matchprodfreq;
2414 totalsel2 += unmatchfreq2 * otherfreq1 / (nd1 - nvalues1);
2416 totalsel2 += otherfreq2 * (otherfreq1 + unmatchfreq1) /
2420 * Use the smaller of the two estimates. This can be justified in
2421 * essentially the same terms as given below for the no-stats case: to
2422 * a first approximation, we are estimating from the point of view of
2423 * the relation with smaller nd.
2425 selec = (totalsel1 < totalsel2) ? totalsel1 : totalsel2;
2430 * We do not have MCV lists for both sides. Estimate the join
2431 * selectivity as MIN(1/nd1,1/nd2)*(1-nullfrac1)*(1-nullfrac2). This
2432 * is plausible if we assume that the join operator is strict and the
2433 * non-null values are about equally distributed: a given non-null
2434 * tuple of rel1 will join to either zero or N2*(1-nullfrac2)/nd2 rows
2435 * of rel2, so total join rows are at most
2436 * N1*(1-nullfrac1)*N2*(1-nullfrac2)/nd2 giving a join selectivity of
2437 * not more than (1-nullfrac1)*(1-nullfrac2)/nd2. By the same logic it
2438 * is not more than (1-nullfrac1)*(1-nullfrac2)/nd1, so the expression
2439 * with MIN() is an upper bound. Using the MIN() means we estimate
2440 * from the point of view of the relation with smaller nd (since the
2441 * larger nd is determining the MIN). It is reasonable to assume that
2442 * most tuples in this rel will have join partners, so the bound is
2443 * probably reasonably tight and should be taken as-is.
2445 * XXX Can we be smarter if we have an MCV list for just one side? It
2446 * seems that if we assume equal distribution for the other side, we
2447 * end up with the same answer anyway.
2449 double nullfrac1 = stats1 ? stats1->stanullfrac : 0.0;
2450 double nullfrac2 = stats2 ? stats2->stanullfrac : 0.0;
2452 selec = (1.0 - nullfrac1) * (1.0 - nullfrac2);
2460 free_attstatsslot(vardata1->atttype, values1, nvalues1,
2461 numbers1, nnumbers1);
2463 free_attstatsslot(vardata2->atttype, values2, nvalues2,
2464 numbers2, nnumbers2);
2470 * eqjoinsel_semi --- eqjoinsel for semi join
2472 * (Also used for anti join, which we are supposed to estimate the same way.)
2473 * Caller has ensured that vardata1 is the LHS variable.
2476 eqjoinsel_semi(Oid operator,
2477 VariableStatData *vardata1, VariableStatData *vardata2,
2478 RelOptInfo *inner_rel)
2485 Form_pg_statistic stats1 = NULL;
2486 bool have_mcvs1 = false;
2487 Datum *values1 = NULL;
2489 float4 *numbers1 = NULL;
2491 bool have_mcvs2 = false;
2492 Datum *values2 = NULL;
2494 float4 *numbers2 = NULL;
2497 nd1 = get_variable_numdistinct(vardata1, &isdefault1);
2498 nd2 = get_variable_numdistinct(vardata2, &isdefault2);
2501 * We clamp nd2 to be not more than what we estimate the inner relation's
2502 * size to be. This is intuitively somewhat reasonable since obviously
2503 * there can't be more than that many distinct values coming from the
2504 * inner rel. The reason for the asymmetry (ie, that we don't clamp nd1
2505 * likewise) is that this is the only pathway by which restriction clauses
2506 * applied to the inner rel will affect the join result size estimate,
2507 * since set_joinrel_size_estimates will multiply SEMI/ANTI selectivity by
2508 * only the outer rel's size. If we clamped nd1 we'd be double-counting
2509 * the selectivity of outer-rel restrictions.
2511 * We can apply this clamping both with respect to the base relation from
2512 * which the join variable comes (if there is just one), and to the
2513 * immediate inner input relation of the current join.
2516 nd2 = Min(nd2, vardata2->rel->rows);
2517 nd2 = Min(nd2, inner_rel->rows);
2519 if (HeapTupleIsValid(vardata1->statsTuple))
2521 stats1 = (Form_pg_statistic) GETSTRUCT(vardata1->statsTuple);
2522 have_mcvs1 = get_attstatsslot(vardata1->statsTuple,
2524 vardata1->atttypmod,
2528 &values1, &nvalues1,
2529 &numbers1, &nnumbers1);
2532 if (HeapTupleIsValid(vardata2->statsTuple))
2534 have_mcvs2 = get_attstatsslot(vardata2->statsTuple,
2536 vardata2->atttypmod,
2540 &values2, &nvalues2,
2541 &numbers2, &nnumbers2);
2544 if (have_mcvs1 && have_mcvs2 && OidIsValid(operator))
2547 * We have most-common-value lists for both relations. Run through
2548 * the lists to see which MCVs actually join to each other with the
2549 * given operator. This allows us to determine the exact join
2550 * selectivity for the portion of the relations represented by the MCV
2551 * lists. We still have to estimate for the remaining population, but
2552 * in a skewed distribution this gives us a big leg up in accuracy.
2557 double nullfrac1 = stats1->stanullfrac;
2566 * The clamping above could have resulted in nd2 being less than
2567 * nvalues2; in which case, we assume that precisely the nd2 most
2568 * common values in the relation will appear in the join input, and so
2569 * compare to only the first nd2 members of the MCV list. Of course
2570 * this is frequently wrong, but it's the best bet we can make.
2572 clamped_nvalues2 = Min(nvalues2, nd2);
2574 fmgr_info(get_opcode(operator), &eqproc);
2575 hasmatch1 = (bool *) palloc0(nvalues1 * sizeof(bool));
2576 hasmatch2 = (bool *) palloc0(clamped_nvalues2 * sizeof(bool));
2579 * Note we assume that each MCV will match at most one member of the
2580 * other MCV list. If the operator isn't really equality, there could
2581 * be multiple matches --- but we don't look for them, both for speed
2582 * and because the math wouldn't add up...
2585 for (i = 0; i < nvalues1; i++)
2589 for (j = 0; j < clamped_nvalues2; j++)
2593 if (DatumGetBool(FunctionCall2Coll(&eqproc,
2594 DEFAULT_COLLATION_OID,
2598 hasmatch1[i] = hasmatch2[j] = true;
2604 /* Sum up frequencies of matched MCVs */
2606 for (i = 0; i < nvalues1; i++)
2609 matchfreq1 += numbers1[i];
2611 CLAMP_PROBABILITY(matchfreq1);
2616 * Now we need to estimate the fraction of relation 1 that has at
2617 * least one join partner. We know for certain that the matched MCVs
2618 * do, so that gives us a lower bound, but we're really in the dark
2619 * about everything else. Our crude approach is: if nd1 <= nd2 then
2620 * assume all non-null rel1 rows have join partners, else assume for
2621 * the uncertain rows that a fraction nd2/nd1 have join partners. We
2622 * can discount the known-matched MCVs from the distinct-values counts
2623 * before doing the division.
2625 * Crude as the above is, it's completely useless if we don't have
2626 * reliable ndistinct values for both sides. Hence, if either nd1 or
2627 * nd2 is default, punt and assume half of the uncertain rows have
2630 if (!isdefault1 && !isdefault2)
2634 if (nd1 <= nd2 || nd2 < 0)
2635 uncertainfrac = 1.0;
2637 uncertainfrac = nd2 / nd1;
2640 uncertainfrac = 0.5;
2641 uncertain = 1.0 - matchfreq1 - nullfrac1;
2642 CLAMP_PROBABILITY(uncertain);
2643 selec = matchfreq1 + uncertainfrac * uncertain;
2648 * Without MCV lists for both sides, we can only use the heuristic
2651 double nullfrac1 = stats1 ? stats1->stanullfrac : 0.0;
2653 if (!isdefault1 && !isdefault2)
2655 if (nd1 <= nd2 || nd2 < 0)
2656 selec = 1.0 - nullfrac1;
2658 selec = (nd2 / nd1) * (1.0 - nullfrac1);
2661 selec = 0.5 * (1.0 - nullfrac1);
2665 free_attstatsslot(vardata1->atttype, values1, nvalues1,
2666 numbers1, nnumbers1);
2668 free_attstatsslot(vardata2->atttype, values2, nvalues2,
2669 numbers2, nnumbers2);
2675 * neqjoinsel - Join selectivity of "!="
2678 neqjoinsel(PG_FUNCTION_ARGS)
2680 PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
2681 Oid operator = PG_GETARG_OID(1);
2682 List *args = (List *) PG_GETARG_POINTER(2);
2683 JoinType jointype = (JoinType) PG_GETARG_INT16(3);
2684 SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) PG_GETARG_POINTER(4);
2689 * We want 1 - eqjoinsel() where the equality operator is the one
2690 * associated with this != operator, that is, its negator.
2692 eqop = get_negator(operator);
2695 result = DatumGetFloat8(DirectFunctionCall5(eqjoinsel,
2696 PointerGetDatum(root),
2697 ObjectIdGetDatum(eqop),
2698 PointerGetDatum(args),
2699 Int16GetDatum(jointype),
2700 PointerGetDatum(sjinfo)));
2704 /* Use default selectivity (should we raise an error instead?) */
2705 result = DEFAULT_EQ_SEL;
2707 result = 1.0 - result;
2708 PG_RETURN_FLOAT8(result);
2712 * scalarltjoinsel - Join selectivity of "<" and "<=" for scalars
2715 scalarltjoinsel(PG_FUNCTION_ARGS)
2717 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
2721 * scalargtjoinsel - Join selectivity of ">" and ">=" for scalars
2724 scalargtjoinsel(PG_FUNCTION_ARGS)
2726 PG_RETURN_FLOAT8(DEFAULT_INEQ_SEL);
2730 * patternjoinsel - Generic code for pattern-match join selectivity.
2733 patternjoinsel(PG_FUNCTION_ARGS, Pattern_Type ptype, bool negate)
2735 /* For the moment we just punt. */
2736 return negate ? (1.0 - DEFAULT_MATCH_SEL) : DEFAULT_MATCH_SEL;
2740 * regexeqjoinsel - Join selectivity of regular-expression pattern match.
2743 regexeqjoinsel(PG_FUNCTION_ARGS)
2745 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Regex, false));
2749 * icregexeqjoinsel - Join selectivity of case-insensitive regex match.
2752 icregexeqjoinsel(PG_FUNCTION_ARGS)
2754 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Regex_IC, false));
2758 * likejoinsel - Join selectivity of LIKE pattern match.
2761 likejoinsel(PG_FUNCTION_ARGS)
2763 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Like, false));
2767 * iclikejoinsel - Join selectivity of ILIKE pattern match.
2770 iclikejoinsel(PG_FUNCTION_ARGS)
2772 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Like_IC, false));
2776 * regexnejoinsel - Join selectivity of regex non-match.
2779 regexnejoinsel(PG_FUNCTION_ARGS)
2781 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Regex, true));
2785 * icregexnejoinsel - Join selectivity of case-insensitive regex non-match.
2788 icregexnejoinsel(PG_FUNCTION_ARGS)
2790 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Regex_IC, true));
2794 * nlikejoinsel - Join selectivity of LIKE pattern non-match.
2797 nlikejoinsel(PG_FUNCTION_ARGS)
2799 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Like, true));
2803 * icnlikejoinsel - Join selectivity of ILIKE pattern non-match.
2806 icnlikejoinsel(PG_FUNCTION_ARGS)
2808 PG_RETURN_FLOAT8(patternjoinsel(fcinfo, Pattern_Type_Like_IC, true));
2812 * mergejoinscansel - Scan selectivity of merge join.
2814 * A merge join will stop as soon as it exhausts either input stream.
2815 * Therefore, if we can estimate the ranges of both input variables,
2816 * we can estimate how much of the input will actually be read. This
2817 * can have a considerable impact on the cost when using indexscans.
2819 * Also, we can estimate how much of each input has to be read before the
2820 * first join pair is found, which will affect the join's startup time.
2822 * clause should be a clause already known to be mergejoinable. opfamily,
2823 * strategy, and nulls_first specify the sort ordering being used.
2826 * *leftstart is set to the fraction of the left-hand variable expected
2827 * to be scanned before the first join pair is found (0 to 1).
2828 * *leftend is set to the fraction of the left-hand variable expected
2829 * to be scanned before the join terminates (0 to 1).
2830 * *rightstart, *rightend similarly for the right-hand variable.
2833 mergejoinscansel(PlannerInfo *root, Node *clause,
2834 Oid opfamily, int strategy, bool nulls_first,
2835 Selectivity *leftstart, Selectivity *leftend,
2836 Selectivity *rightstart, Selectivity *rightend)
2840 VariableStatData leftvar,
2861 /* Set default results if we can't figure anything out. */
2862 /* XXX should default "start" fraction be a bit more than 0? */
2863 *leftstart = *rightstart = 0.0;
2864 *leftend = *rightend = 1.0;
2866 /* Deconstruct the merge clause */
2867 if (!is_opclause(clause))
2868 return; /* shouldn't happen */
2869 opno = ((OpExpr *) clause)->opno;
2870 left = get_leftop((Expr *) clause);
2871 right = get_rightop((Expr *) clause);
2873 return; /* shouldn't happen */
2875 /* Look for stats for the inputs */
2876 examine_variable(root, left, 0, &leftvar);
2877 examine_variable(root, right, 0, &rightvar);
2879 /* Extract the operator's declared left/right datatypes */
2880 get_op_opfamily_properties(opno, opfamily, false,
2884 Assert(op_strategy == BTEqualStrategyNumber);
2887 * Look up the various operators we need. If we don't find them all, it
2888 * probably means the opfamily is broken, but we just fail silently.
2890 * Note: we expect that pg_statistic histograms will be sorted by the '<'
2891 * operator, regardless of which sort direction we are considering.
2895 case BTLessStrategyNumber:
2897 if (op_lefttype == op_righttype)
2900 ltop = get_opfamily_member(opfamily,
2901 op_lefttype, op_righttype,
2902 BTLessStrategyNumber);
2903 leop = get_opfamily_member(opfamily,
2904 op_lefttype, op_righttype,
2905 BTLessEqualStrategyNumber);
2915 ltop = get_opfamily_member(opfamily,
2916 op_lefttype, op_righttype,
2917 BTLessStrategyNumber);
2918 leop = get_opfamily_member(opfamily,
2919 op_lefttype, op_righttype,
2920 BTLessEqualStrategyNumber);
2921 lsortop = get_opfamily_member(opfamily,
2922 op_lefttype, op_lefttype,
2923 BTLessStrategyNumber);
2924 rsortop = get_opfamily_member(opfamily,
2925 op_righttype, op_righttype,
2926 BTLessStrategyNumber);
2929 revltop = get_opfamily_member(opfamily,
2930 op_righttype, op_lefttype,
2931 BTLessStrategyNumber);
2932 revleop = get_opfamily_member(opfamily,
2933 op_righttype, op_lefttype,
2934 BTLessEqualStrategyNumber);
2937 case BTGreaterStrategyNumber:
2938 /* descending-order case */
2940 if (op_lefttype == op_righttype)
2943 ltop = get_opfamily_member(opfamily,
2944 op_lefttype, op_righttype,
2945 BTGreaterStrategyNumber);
2946 leop = get_opfamily_member(opfamily,
2947 op_lefttype, op_righttype,
2948 BTGreaterEqualStrategyNumber);
2951 lstatop = get_opfamily_member(opfamily,
2952 op_lefttype, op_lefttype,
2953 BTLessStrategyNumber);
2960 ltop = get_opfamily_member(opfamily,
2961 op_lefttype, op_righttype,
2962 BTGreaterStrategyNumber);
2963 leop = get_opfamily_member(opfamily,
2964 op_lefttype, op_righttype,
2965 BTGreaterEqualStrategyNumber);
2966 lsortop = get_opfamily_member(opfamily,
2967 op_lefttype, op_lefttype,
2968 BTGreaterStrategyNumber);
2969 rsortop = get_opfamily_member(opfamily,
2970 op_righttype, op_righttype,
2971 BTGreaterStrategyNumber);
2972 lstatop = get_opfamily_member(opfamily,
2973 op_lefttype, op_lefttype,
2974 BTLessStrategyNumber);
2975 rstatop = get_opfamily_member(opfamily,
2976 op_righttype, op_righttype,
2977 BTLessStrategyNumber);
2978 revltop = get_opfamily_member(opfamily,
2979 op_righttype, op_lefttype,
2980 BTGreaterStrategyNumber);
2981 revleop = get_opfamily_member(opfamily,
2982 op_righttype, op_lefttype,
2983 BTGreaterEqualStrategyNumber);
2987 goto fail; /* shouldn't get here */
2990 if (!OidIsValid(lsortop) ||
2991 !OidIsValid(rsortop) ||
2992 !OidIsValid(lstatop) ||
2993 !OidIsValid(rstatop) ||
2994 !OidIsValid(ltop) ||
2995 !OidIsValid(leop) ||
2996 !OidIsValid(revltop) ||
2997 !OidIsValid(revleop))
2998 goto fail; /* insufficient info in catalogs */
3000 /* Try to get ranges of both inputs */
3003 if (!get_variable_range(root, &leftvar, lstatop,
3004 &leftmin, &leftmax))
3005 goto fail; /* no range available from stats */
3006 if (!get_variable_range(root, &rightvar, rstatop,
3007 &rightmin, &rightmax))
3008 goto fail; /* no range available from stats */
3012 /* need to swap the max and min */
3013 if (!get_variable_range(root, &leftvar, lstatop,
3014 &leftmax, &leftmin))
3015 goto fail; /* no range available from stats */
3016 if (!get_variable_range(root, &rightvar, rstatop,
3017 &rightmax, &rightmin))
3018 goto fail; /* no range available from stats */
3022 * Now, the fraction of the left variable that will be scanned is the
3023 * fraction that's <= the right-side maximum value. But only believe
3024 * non-default estimates, else stick with our 1.0.
3026 selec = scalarineqsel(root, leop, isgt, &leftvar,
3027 rightmax, op_righttype);
3028 if (selec != DEFAULT_INEQ_SEL)
3031 /* And similarly for the right variable. */
3032 selec = scalarineqsel(root, revleop, isgt, &rightvar,
3033 leftmax, op_lefttype);
3034 if (selec != DEFAULT_INEQ_SEL)
3038 * Only one of the two "end" fractions can really be less than 1.0;
3039 * believe the smaller estimate and reset the other one to exactly 1.0. If
3040 * we get exactly equal estimates (as can easily happen with self-joins),
3043 if (*leftend > *rightend)
3045 else if (*leftend < *rightend)
3048 *leftend = *rightend = 1.0;
3051 * Also, the fraction of the left variable that will be scanned before the
3052 * first join pair is found is the fraction that's < the right-side
3053 * minimum value. But only believe non-default estimates, else stick with
3056 selec = scalarineqsel(root, ltop, isgt, &leftvar,
3057 rightmin, op_righttype);
3058 if (selec != DEFAULT_INEQ_SEL)
3061 /* And similarly for the right variable. */
3062 selec = scalarineqsel(root, revltop, isgt, &rightvar,
3063 leftmin, op_lefttype);
3064 if (selec != DEFAULT_INEQ_SEL)
3065 *rightstart = selec;
3068 * Only one of the two "start" fractions can really be more than zero;
3069 * believe the larger estimate and reset the other one to exactly 0.0. If
3070 * we get exactly equal estimates (as can easily happen with self-joins),
3073 if (*leftstart < *rightstart)
3075 else if (*leftstart > *rightstart)
3078 *leftstart = *rightstart = 0.0;
3081 * If the sort order is nulls-first, we're going to have to skip over any
3082 * nulls too. These would not have been counted by scalarineqsel, and we
3083 * can safely add in this fraction regardless of whether we believe
3084 * scalarineqsel's results or not. But be sure to clamp the sum to 1.0!
3088 Form_pg_statistic stats;
3090 if (HeapTupleIsValid(leftvar.statsTuple))
3092 stats = (Form_pg_statistic) GETSTRUCT(leftvar.statsTuple);
3093 *leftstart += stats->stanullfrac;
3094 CLAMP_PROBABILITY(*leftstart);
3095 *leftend += stats->stanullfrac;
3096 CLAMP_PROBABILITY(*leftend);
3098 if (HeapTupleIsValid(rightvar.statsTuple))
3100 stats = (Form_pg_statistic) GETSTRUCT(rightvar.statsTuple);
3101 *rightstart += stats->stanullfrac;
3102 CLAMP_PROBABILITY(*rightstart);
3103 *rightend += stats->stanullfrac;
3104 CLAMP_PROBABILITY(*rightend);
3108 /* Disbelieve start >= end, just in case that can happen */
3109 if (*leftstart >= *leftend)
3114 if (*rightstart >= *rightend)
3121 ReleaseVariableStats(leftvar);
3122 ReleaseVariableStats(rightvar);
3127 * Helper routine for estimate_num_groups: add an item to a list of
3128 * GroupVarInfos, but only if it's not known equal to any of the existing
3133 Node *var; /* might be an expression, not just a Var */
3134 RelOptInfo *rel; /* relation it belongs to */
3135 double ndistinct; /* # distinct values */
3139 add_unique_group_var(PlannerInfo *root, List *varinfos,
3140 Node *var, VariableStatData *vardata)
3142 GroupVarInfo *varinfo;
3147 ndistinct = get_variable_numdistinct(vardata, &isdefault);
3149 /* cannot use foreach here because of possible list_delete */
3150 lc = list_head(varinfos);
3153 varinfo = (GroupVarInfo *) lfirst(lc);
3155 /* must advance lc before list_delete possibly pfree's it */
3158 /* Drop exact duplicates */
3159 if (equal(var, varinfo->var))
3163 * Drop known-equal vars, but only if they belong to different
3164 * relations (see comments for estimate_num_groups)
3166 if (vardata->rel != varinfo->rel &&
3167 exprs_known_equal(root, var, varinfo->var))
3169 if (varinfo->ndistinct <= ndistinct)
3171 /* Keep older item, forget new one */
3176 /* Delete the older item */
3177 varinfos = list_delete_ptr(varinfos, varinfo);
3182 varinfo = (GroupVarInfo *) palloc(sizeof(GroupVarInfo));
3185 varinfo->rel = vardata->rel;
3186 varinfo->ndistinct = ndistinct;
3187 varinfos = lappend(varinfos, varinfo);
3192 * estimate_num_groups - Estimate number of groups in a grouped query
3194 * Given a query having a GROUP BY clause, estimate how many groups there
3195 * will be --- ie, the number of distinct combinations of the GROUP BY
3198 * This routine is also used to estimate the number of rows emitted by
3199 * a DISTINCT filtering step; that is an isomorphic problem. (Note:
3200 * actually, we only use it for DISTINCT when there's no grouping or
3201 * aggregation ahead of the DISTINCT.)
3205 * groupExprs - list of expressions being grouped by
3206 * input_rows - number of rows estimated to arrive at the group/unique
3208 * pgset - NULL, or a List** pointing to a grouping set to filter the
3209 * groupExprs against
3211 * Given the lack of any cross-correlation statistics in the system, it's
3212 * impossible to do anything really trustworthy with GROUP BY conditions
3213 * involving multiple Vars. We should however avoid assuming the worst
3214 * case (all possible cross-product terms actually appear as groups) since
3215 * very often the grouped-by Vars are highly correlated. Our current approach
3217 * 1. Expressions yielding boolean are assumed to contribute two groups,
3218 * independently of their content, and are ignored in the subsequent
3219 * steps. This is mainly because tests like "col IS NULL" break the
3220 * heuristic used in step 2 especially badly.
3221 * 2. Reduce the given expressions to a list of unique Vars used. For
3222 * example, GROUP BY a, a + b is treated the same as GROUP BY a, b.
3223 * It is clearly correct not to count the same Var more than once.
3224 * It is also reasonable to treat f(x) the same as x: f() cannot
3225 * increase the number of distinct values (unless it is volatile,
3226 * which we consider unlikely for grouping), but it probably won't
3227 * reduce the number of distinct values much either.
3228 * As a special case, if a GROUP BY expression can be matched to an
3229 * expressional index for which we have statistics, then we treat the
3230 * whole expression as though it were just a Var.
3231 * 3. If the list contains Vars of different relations that are known equal
3232 * due to equivalence classes, then drop all but one of the Vars from each
3233 * known-equal set, keeping the one with smallest estimated # of values
3234 * (since the extra values of the others can't appear in joined rows).
3235 * Note the reason we only consider Vars of different relations is that
3236 * if we considered ones of the same rel, we'd be double-counting the
3237 * restriction selectivity of the equality in the next step.
3238 * 4. For Vars within a single source rel, we multiply together the numbers
3239 * of values, clamp to the number of rows in the rel (divided by 10 if
3240 * more than one Var), and then multiply by a factor based on the
3241 * selectivity of the restriction clauses for that rel. When there's
3242 * more than one Var, the initial product is probably too high (it's the
3243 * worst case) but clamping to a fraction of the rel's rows seems to be a
3244 * helpful heuristic for not letting the estimate get out of hand. (The
3245 * factor of 10 is derived from pre-Postgres-7.4 practice.) The factor
3246 * we multiply by to adjust for the restriction selectivity assumes that
3247 * the restriction clauses are independent of the grouping, which may not
3248 * be a valid assumption, but it's hard to do better.
3249 * 5. If there are Vars from multiple rels, we repeat step 4 for each such
3250 * rel, and multiply the results together.
3251 * Note that rels not containing grouped Vars are ignored completely, as are
3252 * join clauses. Such rels cannot increase the number of groups, and we
3253 * assume such clauses do not reduce the number either (somewhat bogus,
3254 * but we don't have the info to do better).
3257 estimate_num_groups(PlannerInfo *root, List *groupExprs, double input_rows,
3260 List *varinfos = NIL;
3266 * We don't ever want to return an estimate of zero groups, as that tends
3267 * to lead to division-by-zero and other unpleasantness. The input_rows
3268 * estimate is usually already at least 1, but clamp it just in case it
3271 input_rows = clamp_row_est(input_rows);
3274 * If no grouping columns, there's exactly one group. (This can't happen
3275 * for normal cases with GROUP BY or DISTINCT, but it is possible for
3276 * corner cases with set operations.)
3278 if (groupExprs == NIL || (pgset && list_length(*pgset) < 1))
3282 * Count groups derived from boolean grouping expressions. For other
3283 * expressions, find the unique Vars used, treating an expression as a Var
3284 * if we can find stats for it. For each one, record the statistical
3285 * estimate of number of distinct values (total in its table, without
3286 * regard for filtering).
3291 foreach(l, groupExprs)
3293 Node *groupexpr = (Node *) lfirst(l);
3294 VariableStatData vardata;
3298 /* is expression in this grouping set? */
3299 if (pgset && !list_member_int(*pgset, i++))
3302 /* Short-circuit for expressions returning boolean */
3303 if (exprType(groupexpr) == BOOLOID)
3310 * If examine_variable is able to deduce anything about the GROUP BY
3311 * expression, treat it as a single variable even if it's really more
3314 examine_variable(root, groupexpr, 0, &vardata);
3315 if (HeapTupleIsValid(vardata.statsTuple) || vardata.isunique)
3317 varinfos = add_unique_group_var(root, varinfos,
3318 groupexpr, &vardata);
3319 ReleaseVariableStats(vardata);
3322 ReleaseVariableStats(vardata);
3325 * Else pull out the component Vars. Handle PlaceHolderVars by
3326 * recursing into their arguments (effectively assuming that the
3327 * PlaceHolderVar doesn't change the number of groups, which boils
3328 * down to ignoring the possible addition of nulls to the result set).
3330 varshere = pull_var_clause(groupexpr,
3331 PVC_RECURSE_AGGREGATES |
3332 PVC_RECURSE_WINDOWFUNCS |
3333 PVC_RECURSE_PLACEHOLDERS);
3336 * If we find any variable-free GROUP BY item, then either it is a
3337 * constant (and we can ignore it) or it contains a volatile function;
3338 * in the latter case we punt and assume that each input row will
3339 * yield a distinct group.
3341 if (varshere == NIL)
3343 if (contain_volatile_functions(groupexpr))
3349 * Else add variables to varinfos list
3351 foreach(l2, varshere)
3353 Node *var = (Node *) lfirst(l2);
3355 examine_variable(root, var, 0, &vardata);
3356 varinfos = add_unique_group_var(root, varinfos, var, &vardata);
3357 ReleaseVariableStats(vardata);
3362 * If now no Vars, we must have an all-constant or all-boolean GROUP BY
3365 if (varinfos == NIL)
3367 /* Guard against out-of-range answers */
3368 if (numdistinct > input_rows)
3369 numdistinct = input_rows;
3374 * Group Vars by relation and estimate total numdistinct.
3376 * For each iteration of the outer loop, we process the frontmost Var in
3377 * varinfos, plus all other Vars in the same relation. We remove these
3378 * Vars from the newvarinfos list for the next iteration. This is the
3379 * easiest way to group Vars of same rel together.
3383 GroupVarInfo *varinfo1 = (GroupVarInfo *) linitial(varinfos);
3384 RelOptInfo *rel = varinfo1->rel;
3385 double reldistinct = varinfo1->ndistinct;
3386 double relmaxndistinct = reldistinct;
3387 int relvarcount = 1;
3388 List *newvarinfos = NIL;
3391 * Get the product of numdistinct estimates of the Vars for this rel.
3392 * Also, construct new varinfos list of remaining Vars.
3394 for_each_cell(l, lnext(list_head(varinfos)))
3396 GroupVarInfo *varinfo2 = (GroupVarInfo *) lfirst(l);
3398 if (varinfo2->rel == varinfo1->rel)
3400 reldistinct *= varinfo2->ndistinct;
3401 if (relmaxndistinct < varinfo2->ndistinct)
3402 relmaxndistinct = varinfo2->ndistinct;
3407 /* not time to process varinfo2 yet */
3408 newvarinfos = lcons(varinfo2, newvarinfos);
3413 * Sanity check --- don't divide by zero if empty relation.
3415 Assert(rel->reloptkind == RELOPT_BASEREL);
3416 if (rel->tuples > 0)
3419 * Clamp to size of rel, or size of rel / 10 if multiple Vars. The
3420 * fudge factor is because the Vars are probably correlated but we
3421 * don't know by how much. We should never clamp to less than the
3422 * largest ndistinct value for any of the Vars, though, since
3423 * there will surely be at least that many groups.
3425 double clamp = rel->tuples;
3427 if (relvarcount > 1)
3430 if (clamp < relmaxndistinct)
3432 clamp = relmaxndistinct;
3433 /* for sanity in case some ndistinct is too large: */
3434 if (clamp > rel->tuples)
3435 clamp = rel->tuples;
3438 if (reldistinct > clamp)
3439 reldistinct = clamp;
3442 * Update the estimate based on the restriction selectivity,
3443 * guarding against division by zero when reldistinct is zero.
3444 * Also skip this if we know that we are returning all rows.
3446 if (reldistinct > 0 && rel->rows < rel->tuples)
3449 * Given a table containing N rows with n distinct values in a
3450 * uniform distribution, if we select p rows at random then
3451 * the expected number of distinct values selected is
3453 * n * (1 - product((N-N/n-i)/(N-i), i=0..p-1))
3455 * = n * (1 - (N-N/n)! / (N-N/n-p)! * (N-p)! / N!)
3457 * See "Approximating block accesses in database
3458 * organizations", S. B. Yao, Communications of the ACM,
3459 * Volume 20 Issue 4, April 1977 Pages 260-261.
3461 * Alternatively, re-arranging the terms from the factorials,
3462 * this may be written as
3464 * n * (1 - product((N-p-i)/(N-i), i=0..N/n-1))
3466 * This form of the formula is more efficient to compute in
3467 * the common case where p is larger than N/n. Additionally,
3468 * as pointed out by Dell'Era, if i << N for all terms in the
3469 * product, it can be approximated by
3471 * n * (1 - ((N-p)/N)^(N/n))
3473 * See "Expected distinct values when selecting from a bag
3474 * without replacement", Alberto Dell'Era,
3475 * http://www.adellera.it/investigations/distinct_balls/.
3477 * The condition i << N is equivalent to n >> 1, so this is a
3478 * good approximation when the number of distinct values in
3479 * the table is large. It turns out that this formula also
3480 * works well even when n is small.
3483 (1 - pow((rel->tuples - rel->rows) / rel->tuples,
3484 rel->tuples / reldistinct));
3486 reldistinct = clamp_row_est(reldistinct);
3489 * Update estimate of total distinct groups.
3491 numdistinct *= reldistinct;
3494 varinfos = newvarinfos;
3495 } while (varinfos != NIL);
3497 numdistinct = ceil(numdistinct);
3499 /* Guard against out-of-range answers */
3500 if (numdistinct > input_rows)
3501 numdistinct = input_rows;
3502 if (numdistinct < 1.0)
3509 * Estimate hash bucketsize fraction (ie, number of entries in a bucket
3510 * divided by total tuples in relation) if the specified expression is used
3513 * XXX This is really pretty bogus since we're effectively assuming that the
3514 * distribution of hash keys will be the same after applying restriction
3515 * clauses as it was in the underlying relation. However, we are not nearly
3516 * smart enough to figure out how the restrict clauses might change the
3517 * distribution, so this will have to do for now.
3519 * We are passed the number of buckets the executor will use for the given
3520 * input relation. If the data were perfectly distributed, with the same
3521 * number of tuples going into each available bucket, then the bucketsize
3522 * fraction would be 1/nbuckets. But this happy state of affairs will occur
3523 * only if (a) there are at least nbuckets distinct data values, and (b)
3524 * we have a not-too-skewed data distribution. Otherwise the buckets will
3525 * be nonuniformly occupied. If the other relation in the join has a key
3526 * distribution similar to this one's, then the most-loaded buckets are
3527 * exactly those that will be probed most often. Therefore, the "average"
3528 * bucket size for costing purposes should really be taken as something close
3529 * to the "worst case" bucket size. We try to estimate this by adjusting the
3530 * fraction if there are too few distinct data values, and then scaling up
3531 * by the ratio of the most common value's frequency to the average frequency.
3533 * If no statistics are available, use a default estimate of 0.1. This will
3534 * discourage use of a hash rather strongly if the inner relation is large,
3535 * which is what we want. We do not want to hash unless we know that the
3536 * inner rel is well-dispersed (or the alternatives seem much worse).
3539 estimate_hash_bucketsize(PlannerInfo *root, Node *hashkey, double nbuckets)
3541 VariableStatData vardata;
3551 examine_variable(root, hashkey, 0, &vardata);
3553 /* Get number of distinct values */
3554 ndistinct = get_variable_numdistinct(&vardata, &isdefault);
3556 /* If ndistinct isn't real, punt and return 0.1, per comments above */
3559 ReleaseVariableStats(vardata);
3560 return (Selectivity) 0.1;
3563 /* Get fraction that are null */
3564 if (HeapTupleIsValid(vardata.statsTuple))
3566 Form_pg_statistic stats;
3568 stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
3569 stanullfrac = stats->stanullfrac;
3574 /* Compute avg freq of all distinct data values in raw relation */
3575 avgfreq = (1.0 - stanullfrac) / ndistinct;
3578 * Adjust ndistinct to account for restriction clauses. Observe we are
3579 * assuming that the data distribution is affected uniformly by the
3580 * restriction clauses!
3582 * XXX Possibly better way, but much more expensive: multiply by
3583 * selectivity of rel's restriction clauses that mention the target Var.
3585 if (vardata.rel && vardata.rel->tuples > 0)
3587 ndistinct *= vardata.rel->rows / vardata.rel->tuples;
3588 ndistinct = clamp_row_est(ndistinct);
3592 * Initial estimate of bucketsize fraction is 1/nbuckets as long as the
3593 * number of buckets is less than the expected number of distinct values;
3594 * otherwise it is 1/ndistinct.
3596 if (ndistinct > nbuckets)
3597 estfract = 1.0 / nbuckets;
3599 estfract = 1.0 / ndistinct;
3602 * Look up the frequency of the most common value, if available.
3606 if (HeapTupleIsValid(vardata.statsTuple))
3608 if (get_attstatsslot(vardata.statsTuple,
3609 vardata.atttype, vardata.atttypmod,
3610 STATISTIC_KIND_MCV, InvalidOid,
3613 &numbers, &nnumbers))
3616 * The first MCV stat is for the most common value.
3619 mcvfreq = numbers[0];
3620 free_attstatsslot(vardata.atttype, NULL, 0,
3626 * Adjust estimated bucketsize upward to account for skewed distribution.
3628 if (avgfreq > 0.0 && mcvfreq > avgfreq)
3629 estfract *= mcvfreq / avgfreq;
3632 * Clamp bucketsize to sane range (the above adjustment could easily
3633 * produce an out-of-range result). We set the lower bound a little above
3634 * zero, since zero isn't a very sane result.
3636 if (estfract < 1.0e-6)
3638 else if (estfract > 1.0)
3641 ReleaseVariableStats(vardata);
3643 return (Selectivity) estfract;
3647 /*-------------------------------------------------------------------------
3651 *-------------------------------------------------------------------------
3656 * Convert non-NULL values of the indicated types to the comparison
3657 * scale needed by scalarineqsel().
3658 * Returns "true" if successful.
3660 * XXX this routine is a hack: ideally we should look up the conversion
3661 * subroutines in pg_type.
3663 * All numeric datatypes are simply converted to their equivalent
3664 * "double" values. (NUMERIC values that are outside the range of "double"
3665 * are clamped to +/- HUGE_VAL.)
3667 * String datatypes are converted by convert_string_to_scalar(),
3668 * which is explained below. The reason why this routine deals with
3669 * three values at a time, not just one, is that we need it for strings.
3671 * The bytea datatype is just enough different from strings that it has
3672 * to be treated separately.
3674 * The several datatypes representing absolute times are all converted
3675 * to Timestamp, which is actually a double, and then we just use that
3676 * double value. Note this will give correct results even for the "special"
3677 * values of Timestamp, since those are chosen to compare correctly;
3678 * see timestamp_cmp.
3680 * The several datatypes representing relative times (intervals) are all
3681 * converted to measurements expressed in seconds.
3684 convert_to_scalar(Datum value, Oid valuetypid, double *scaledvalue,
3685 Datum lobound, Datum hibound, Oid boundstypid,
3686 double *scaledlobound, double *scaledhibound)
3689 * Both the valuetypid and the boundstypid should exactly match the
3690 * declared input type(s) of the operator we are invoked for, so we just
3691 * error out if either is not recognized.
3693 * XXX The histogram we are interpolating between points of could belong
3694 * to a column that's only binary-compatible with the declared type. In
3695 * essence we are assuming that the semantics of binary-compatible types
3696 * are enough alike that we can use a histogram generated with one type's
3697 * operators to estimate selectivity for the other's. This is outright
3698 * wrong in some cases --- in particular signed versus unsigned
3699 * interpretation could trip us up. But it's useful enough in the
3700 * majority of cases that we do it anyway. Should think about more
3701 * rigorous ways to do it.
3706 * Built-in numeric types
3717 case REGPROCEDUREOID:
3719 case REGOPERATOROID:
3723 case REGDICTIONARYOID:
3725 case REGNAMESPACEOID:
3726 *scaledvalue = convert_numeric_to_scalar(value, valuetypid);
3727 *scaledlobound = convert_numeric_to_scalar(lobound, boundstypid);
3728 *scaledhibound = convert_numeric_to_scalar(hibound, boundstypid);
3732 * Built-in string types
3740 char *valstr = convert_string_datum(value, valuetypid);
3741 char *lostr = convert_string_datum(lobound, boundstypid);
3742 char *histr = convert_string_datum(hibound, boundstypid);
3744 convert_string_to_scalar(valstr, scaledvalue,
3745 lostr, scaledlobound,
3746 histr, scaledhibound);
3754 * Built-in bytea type
3758 convert_bytea_to_scalar(value, scaledvalue,
3759 lobound, scaledlobound,
3760 hibound, scaledhibound);
3765 * Built-in time types
3768 case TIMESTAMPTZOID:
3776 *scaledvalue = convert_timevalue_to_scalar(value, valuetypid);
3777 *scaledlobound = convert_timevalue_to_scalar(lobound, boundstypid);
3778 *scaledhibound = convert_timevalue_to_scalar(hibound, boundstypid);
3782 * Built-in network types
3787 *scaledvalue = convert_network_to_scalar(value, valuetypid);
3788 *scaledlobound = convert_network_to_scalar(lobound, boundstypid);
3789 *scaledhibound = convert_network_to_scalar(hibound, boundstypid);
3792 /* Don't know how to convert */
3793 *scaledvalue = *scaledlobound = *scaledhibound = 0;
3798 * Do convert_to_scalar()'s work for any numeric data type.
3801 convert_numeric_to_scalar(Datum value, Oid typid)
3806 return (double) DatumGetBool(value);
3808 return (double) DatumGetInt16(value);
3810 return (double) DatumGetInt32(value);
3812 return (double) DatumGetInt64(value);
3814 return (double) DatumGetFloat4(value);
3816 return (double) DatumGetFloat8(value);
3818 /* Note: out-of-range values will be clamped to +-HUGE_VAL */
3820 DatumGetFloat8(DirectFunctionCall1(numeric_float8_no_overflow,
3824 case REGPROCEDUREOID:
3826 case REGOPERATOROID:
3830 case REGDICTIONARYOID:
3832 case REGNAMESPACEOID:
3833 /* we can treat OIDs as integers... */
3834 return (double) DatumGetObjectId(value);
3838 * Can't get here unless someone tries to use scalarltsel/scalargtsel on
3839 * an operator with one numeric and one non-numeric operand.
3841 elog(ERROR, "unsupported type: %u", typid);
3846 * Do convert_to_scalar()'s work for any character-string data type.
3848 * String datatypes are converted to a scale that ranges from 0 to 1,
3849 * where we visualize the bytes of the string as fractional digits.
3851 * We do not want the base to be 256, however, since that tends to
3852 * generate inflated selectivity estimates; few databases will have
3853 * occurrences of all 256 possible byte values at each position.
3854 * Instead, use the smallest and largest byte values seen in the bounds
3855 * as the estimated range for each byte, after some fudging to deal with
3856 * the fact that we probably aren't going to see the full range that way.
3858 * An additional refinement is that we discard any common prefix of the
3859 * three strings before computing the scaled values. This allows us to
3860 * "zoom in" when we encounter a narrow data range. An example is a phone
3861 * number database where all the values begin with the same area code.
3862 * (Actually, the bounds will be adjacent histogram-bin-boundary values,
3863 * so this is more likely to happen than you might think.)
3866 convert_string_to_scalar(char *value,
3867 double *scaledvalue,
3869 double *scaledlobound,
3871 double *scaledhibound)
3877 rangelo = rangehi = (unsigned char) hibound[0];
3878 for (sptr = lobound; *sptr; sptr++)
3880 if (rangelo > (unsigned char) *sptr)
3881 rangelo = (unsigned char) *sptr;
3882 if (rangehi < (unsigned char) *sptr)
3883 rangehi = (unsigned char) *sptr;
3885 for (sptr = hibound; *sptr; sptr++)
3887 if (rangelo > (unsigned char) *sptr)
3888 rangelo = (unsigned char) *sptr;
3889 if (rangehi < (unsigned char) *sptr)
3890 rangehi = (unsigned char) *sptr;
3892 /* If range includes any upper-case ASCII chars, make it include all */
3893 if (rangelo <= 'Z' && rangehi >= 'A')
3900 /* Ditto lower-case */
3901 if (rangelo <= 'z' && rangehi >= 'a')
3909 if (rangelo <= '9' && rangehi >= '0')
3918 * If range includes less than 10 chars, assume we have not got enough
3919 * data, and make it include regular ASCII set.
3921 if (rangehi - rangelo < 9)
3928 * Now strip any common prefix of the three strings.
3932 if (*lobound != *hibound || *lobound != *value)
3934 lobound++, hibound++, value++;
3938 * Now we can do the conversions.
3940 *scaledvalue = convert_one_string_to_scalar(value, rangelo, rangehi);
3941 *scaledlobound = convert_one_string_to_scalar(lobound, rangelo, rangehi);
3942 *scaledhibound = convert_one_string_to_scalar(hibound, rangelo, rangehi);
3946 convert_one_string_to_scalar(char *value, int rangelo, int rangehi)
3948 int slen = strlen(value);
3954 return 0.0; /* empty string has scalar value 0 */
3957 * There seems little point in considering more than a dozen bytes from
3958 * the string. Since base is at least 10, that will give us nominal
3959 * resolution of at least 12 decimal digits, which is surely far more
3960 * precision than this estimation technique has got anyway (especially in
3961 * non-C locales). Also, even with the maximum possible base of 256, this
3962 * ensures denom cannot grow larger than 256^13 = 2.03e31, which will not
3963 * overflow on any known machine.
3968 /* Convert initial characters to fraction */
3969 base = rangehi - rangelo + 1;
3974 int ch = (unsigned char) *value++;
3978 else if (ch > rangehi)
3980 num += ((double) (ch - rangelo)) / denom;
3988 * Convert a string-type Datum into a palloc'd, null-terminated string.
3990 * When using a non-C locale, we must pass the string through strxfrm()
3991 * before continuing, so as to generate correct locale-specific results.
3994 convert_string_datum(Datum value, Oid typid)
4001 val = (char *) palloc(2);
4002 val[0] = DatumGetChar(value);
4008 val = TextDatumGetCString(value);
4012 NameData *nm = (NameData *) DatumGetPointer(value);
4014 val = pstrdup(NameStr(*nm));
4020 * Can't get here unless someone tries to use scalarltsel on an
4021 * operator with one string and one non-string operand.
4023 elog(ERROR, "unsupported type: %u", typid);
4027 if (!lc_collate_is_c(DEFAULT_COLLATION_OID))
4031 size_t xfrmlen2 PG_USED_FOR_ASSERTS_ONLY;
4034 * XXX: We could guess at a suitable output buffer size and only call
4035 * strxfrm twice if our guess is too small.
4037 * XXX: strxfrm doesn't support UTF-8 encoding on Win32, it can return
4038 * bogus data or set an error. This is not really a problem unless it
4039 * crashes since it will only give an estimation error and nothing
4042 #if _MSC_VER == 1400 /* VS.Net 2005 */
4046 * http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?
4047 * FeedbackID=99694 */
4051 xfrmlen = strxfrm(x, val, 0);
4054 xfrmlen = strxfrm(NULL, val, 0);
4059 * On Windows, strxfrm returns INT_MAX when an error occurs. Instead
4060 * of trying to allocate this much memory (and fail), just return the
4061 * original string unmodified as if we were in the C locale.
4063 if (xfrmlen == INT_MAX)
4066 xfrmstr = (char *) palloc(xfrmlen + 1);
4067 xfrmlen2 = strxfrm(xfrmstr, val, xfrmlen + 1);
4070 * Some systems (e.g., glibc) can return a smaller value from the
4071 * second call than the first; thus the Assert must be <= not ==.
4073 Assert(xfrmlen2 <= xfrmlen);
4082 * Do convert_to_scalar()'s work for any bytea data type.
4084 * Very similar to convert_string_to_scalar except we can't assume
4085 * null-termination and therefore pass explicit lengths around.
4087 * Also, assumptions about likely "normal" ranges of characters have been
4088 * removed - a data range of 0..255 is always used, for now. (Perhaps
4089 * someday we will add information about actual byte data range to
4093 convert_bytea_to_scalar(Datum value,
4094 double *scaledvalue,
4096 double *scaledlobound,
4098 double *scaledhibound)
4102 valuelen = VARSIZE(DatumGetPointer(value)) - VARHDRSZ,
4103 loboundlen = VARSIZE(DatumGetPointer(lobound)) - VARHDRSZ,
4104 hiboundlen = VARSIZE(DatumGetPointer(hibound)) - VARHDRSZ,
4107 unsigned char *valstr = (unsigned char *) VARDATA(DatumGetPointer(value)),
4108 *lostr = (unsigned char *) VARDATA(DatumGetPointer(lobound)),
4109 *histr = (unsigned char *) VARDATA(DatumGetPointer(hibound));
4112 * Assume bytea data is uniformly distributed across all byte values.
4118 * Now strip any common prefix of the three strings.
4120 minlen = Min(Min(valuelen, loboundlen), hiboundlen);
4121 for (i = 0; i < minlen; i++)
4123 if (*lostr != *histr || *lostr != *valstr)
4125 lostr++, histr++, valstr++;
4126 loboundlen--, hiboundlen--, valuelen--;
4130 * Now we can do the conversions.
4132 *scaledvalue = convert_one_bytea_to_scalar(valstr, valuelen, rangelo, rangehi);
4133 *scaledlobound = convert_one_bytea_to_scalar(lostr, loboundlen, rangelo, rangehi);
4134 *scaledhibound = convert_one_bytea_to_scalar(histr, hiboundlen, rangelo, rangehi);
4138 convert_one_bytea_to_scalar(unsigned char *value, int valuelen,
4139 int rangelo, int rangehi)
4146 return 0.0; /* empty string has scalar value 0 */
4149 * Since base is 256, need not consider more than about 10 chars (even
4150 * this many seems like overkill)
4155 /* Convert initial characters to fraction */
4156 base = rangehi - rangelo + 1;
4159 while (valuelen-- > 0)
4165 else if (ch > rangehi)
4167 num += ((double) (ch - rangelo)) / denom;
4175 * Do convert_to_scalar()'s work for any timevalue data type.
4178 convert_timevalue_to_scalar(Datum value, Oid typid)
4183 return DatumGetTimestamp(value);
4184 case TIMESTAMPTZOID:
4185 return DatumGetTimestampTz(value);
4187 return DatumGetTimestamp(DirectFunctionCall1(abstime_timestamp,
4190 return date2timestamp_no_overflow(DatumGetDateADT(value));
4193 Interval *interval = DatumGetIntervalP(value);
4196 * Convert the month part of Interval to days using assumed
4197 * average month length of 365.25/12.0 days. Not too
4198 * accurate, but plenty good enough for our purposes.
4200 #ifdef HAVE_INT64_TIMESTAMP
4201 return interval->time + interval->day * (double) USECS_PER_DAY +
4202 interval->month * ((DAYS_PER_YEAR / (double) MONTHS_PER_YEAR) * USECS_PER_DAY);
4204 return interval->time + interval->day * SECS_PER_DAY +
4205 interval->month * ((DAYS_PER_YEAR / (double) MONTHS_PER_YEAR) * (double) SECS_PER_DAY);
4209 #ifdef HAVE_INT64_TIMESTAMP
4210 return (DatumGetRelativeTime(value) * 1000000.0);
4212 return DatumGetRelativeTime(value);
4216 TimeInterval tinterval = DatumGetTimeInterval(value);
4218 #ifdef HAVE_INT64_TIMESTAMP
4219 if (tinterval->status != 0)
4220 return ((tinterval->data[1] - tinterval->data[0]) * 1000000.0);
4222 if (tinterval->status != 0)
4223 return tinterval->data[1] - tinterval->data[0];
4225 return 0; /* for lack of a better idea */
4228 return DatumGetTimeADT(value);
4231 TimeTzADT *timetz = DatumGetTimeTzADTP(value);
4233 /* use GMT-equivalent time */
4234 #ifdef HAVE_INT64_TIMESTAMP
4235 return (double) (timetz->time + (timetz->zone * 1000000.0));
4237 return (double) (timetz->time + timetz->zone);
4243 * Can't get here unless someone tries to use scalarltsel/scalargtsel on
4244 * an operator with one timevalue and one non-timevalue operand.
4246 elog(ERROR, "unsupported type: %u", typid);
4252 * get_restriction_variable
4253 * Examine the args of a restriction clause to see if it's of the
4254 * form (variable op pseudoconstant) or (pseudoconstant op variable),
4255 * where "variable" could be either a Var or an expression in vars of a
4256 * single relation. If so, extract information about the variable,
4257 * and also indicate which side it was on and the other argument.
4260 * root: the planner info
4261 * args: clause argument list
4262 * varRelid: see specs for restriction selectivity functions
4264 * Outputs: (these are valid only if TRUE is returned)
4265 * *vardata: gets information about variable (see examine_variable)
4266 * *other: gets other clause argument, aggressively reduced to a constant
4267 * *varonleft: set TRUE if variable is on the left, FALSE if on the right
4269 * Returns TRUE if a variable is identified, otherwise FALSE.
4271 * Note: if there are Vars on both sides of the clause, we must fail, because
4272 * callers are expecting that the other side will act like a pseudoconstant.
4275 get_restriction_variable(PlannerInfo *root, List *args, int varRelid,
4276 VariableStatData *vardata, Node **other,
4281 VariableStatData rdata;
4283 /* Fail if not a binary opclause (probably shouldn't happen) */
4284 if (list_length(args) != 2)
4287 left = (Node *) linitial(args);
4288 right = (Node *) lsecond(args);
4291 * Examine both sides. Note that when varRelid is nonzero, Vars of other
4292 * relations will be treated as pseudoconstants.
4294 examine_variable(root, left, varRelid, vardata);
4295 examine_variable(root, right, varRelid, &rdata);
4298 * If one side is a variable and the other not, we win.
4300 if (vardata->rel && rdata.rel == NULL)
4303 *other = estimate_expression_value(root, rdata.var);
4304 /* Assume we need no ReleaseVariableStats(rdata) here */
4308 if (vardata->rel == NULL && rdata.rel)
4311 *other = estimate_expression_value(root, vardata->var);
4312 /* Assume we need no ReleaseVariableStats(*vardata) here */
4317 /* Ooops, clause has wrong structure (probably var op var) */
4318 ReleaseVariableStats(*vardata);
4319 ReleaseVariableStats(rdata);
4325 * get_join_variables
4326 * Apply examine_variable() to each side of a join clause.
4327 * Also, attempt to identify whether the join clause has the same
4328 * or reversed sense compared to the SpecialJoinInfo.
4330 * We consider the join clause "normal" if it is "lhs_var OP rhs_var",
4331 * or "reversed" if it is "rhs_var OP lhs_var". In complicated cases
4332 * where we can't tell for sure, we default to assuming it's normal.
4335 get_join_variables(PlannerInfo *root, List *args, SpecialJoinInfo *sjinfo,
4336 VariableStatData *vardata1, VariableStatData *vardata2,
4337 bool *join_is_reversed)
4342 if (list_length(args) != 2)
4343 elog(ERROR, "join operator should take two arguments");
4345 left = (Node *) linitial(args);
4346 right = (Node *) lsecond(args);
4348 examine_variable(root, left, 0, vardata1);
4349 examine_variable(root, right, 0, vardata2);
4351 if (vardata1->rel &&
4352 bms_is_subset(vardata1->rel->relids, sjinfo->syn_righthand))
4353 *join_is_reversed = true; /* var1 is on RHS */
4354 else if (vardata2->rel &&
4355 bms_is_subset(vardata2->rel->relids, sjinfo->syn_lefthand))
4356 *join_is_reversed = true; /* var2 is on LHS */
4358 *join_is_reversed = false;
4363 * Try to look up statistical data about an expression.
4364 * Fill in a VariableStatData struct to describe the expression.
4367 * root: the planner info
4368 * node: the expression tree to examine
4369 * varRelid: see specs for restriction selectivity functions
4371 * Outputs: *vardata is filled as follows:
4372 * var: the input expression (with any binary relabeling stripped, if
4373 * it is or contains a variable; but otherwise the type is preserved)
4374 * rel: RelOptInfo for relation containing variable; NULL if expression
4375 * contains no Vars (NOTE this could point to a RelOptInfo of a
4376 * subquery, not one in the current query).
4377 * statsTuple: the pg_statistic entry for the variable, if one exists;
4379 * freefunc: pointer to a function to release statsTuple with.
4380 * vartype: exposed type of the expression; this should always match
4381 * the declared input type of the operator we are estimating for.
4382 * atttype, atttypmod: type data to pass to get_attstatsslot(). This is
4383 * commonly the same as the exposed type of the variable argument,
4384 * but can be different in binary-compatible-type cases.
4385 * isunique: TRUE if we were able to match the var to a unique index or a
4386 * single-column DISTINCT clause, implying its values are unique for
4387 * this query. (Caution: this should be trusted for statistical
4388 * purposes only, since we do not check indimmediate nor verify that
4389 * the exact same definition of equality applies.)
4391 * Caller is responsible for doing ReleaseVariableStats() before exiting.
4394 examine_variable(PlannerInfo *root, Node *node, int varRelid,
4395 VariableStatData *vardata)
4401 /* Make sure we don't return dangling pointers in vardata */
4402 MemSet(vardata, 0, sizeof(VariableStatData));
4404 /* Save the exposed type of the expression */
4405 vardata->vartype = exprType(node);
4407 /* Look inside any binary-compatible relabeling */
4409 if (IsA(node, RelabelType))
4410 basenode = (Node *) ((RelabelType *) node)->arg;
4414 /* Fast path for a simple Var */
4416 if (IsA(basenode, Var) &&
4417 (varRelid == 0 || varRelid == ((Var *) basenode)->varno))
4419 Var *var = (Var *) basenode;
4421 /* Set up result fields other than the stats tuple */
4422 vardata->var = basenode; /* return Var without relabeling */
4423 vardata->rel = find_base_rel(root, var->varno);
4424 vardata->atttype = var->vartype;
4425 vardata->atttypmod = var->vartypmod;
4426 vardata->isunique = has_unique_index(vardata->rel, var->varattno);
4428 /* Try to locate some stats */
4429 examine_simple_variable(root, var, vardata);
4435 * Okay, it's a more complicated expression. Determine variable
4436 * membership. Note that when varRelid isn't zero, only vars of that
4437 * relation are considered "real" vars.
4439 varnos = pull_varnos(basenode);
4443 switch (bms_membership(varnos))
4446 /* No Vars at all ... must be pseudo-constant clause */
4449 if (varRelid == 0 || bms_is_member(varRelid, varnos))
4451 onerel = find_base_rel(root,
4452 (varRelid ? varRelid : bms_singleton_member(varnos)));
4453 vardata->rel = onerel;
4454 node = basenode; /* strip any relabeling */
4456 /* else treat it as a constant */
4461 /* treat it as a variable of a join relation */
4462 vardata->rel = find_join_rel(root, varnos);
4463 node = basenode; /* strip any relabeling */
4465 else if (bms_is_member(varRelid, varnos))
4467 /* ignore the vars belonging to other relations */
4468 vardata->rel = find_base_rel(root, varRelid);
4469 node = basenode; /* strip any relabeling */
4470 /* note: no point in expressional-index search here */
4472 /* else treat it as a constant */
4478 vardata->var = node;
4479 vardata->atttype = exprType(node);
4480 vardata->atttypmod = exprTypmod(node);
4485 * We have an expression in vars of a single relation. Try to match
4486 * it to expressional index columns, in hopes of finding some
4489 * XXX it's conceivable that there are multiple matches with different
4490 * index opfamilies; if so, we need to pick one that matches the
4491 * operator we are estimating for. FIXME later.
4495 foreach(ilist, onerel->indexlist)
4497 IndexOptInfo *index = (IndexOptInfo *) lfirst(ilist);
4498 ListCell *indexpr_item;
4501 indexpr_item = list_head(index->indexprs);
4502 if (indexpr_item == NULL)
4503 continue; /* no expressions here... */
4505 for (pos = 0; pos < index->ncolumns; pos++)
4507 if (index->indexkeys[pos] == 0)
4511 if (indexpr_item == NULL)
4512 elog(ERROR, "too few entries in indexprs list");
4513 indexkey = (Node *) lfirst(indexpr_item);
4514 if (indexkey && IsA(indexkey, RelabelType))
4515 indexkey = (Node *) ((RelabelType *) indexkey)->arg;
4516 if (equal(node, indexkey))
4519 * Found a match ... is it a unique index? Tests here
4520 * should match has_unique_index().
4522 if (index->unique &&
4523 index->ncolumns == 1 &&
4524 (index->indpred == NIL || index->predOK))
4525 vardata->isunique = true;
4528 * Has it got stats? We only consider stats for
4529 * non-partial indexes, since partial indexes probably
4530 * don't reflect whole-relation statistics; the above
4531 * check for uniqueness is the only info we take from
4534 * An index stats hook, however, must make its own
4535 * decisions about what to do with partial indexes.
4537 if (get_index_stats_hook &&
4538 (*get_index_stats_hook) (root, index->indexoid,
4542 * The hook took control of acquiring a stats
4543 * tuple. If it did supply a tuple, it'd better
4544 * have supplied a freefunc.
4546 if (HeapTupleIsValid(vardata->statsTuple) &&
4548 elog(ERROR, "no function provided to release variable stats with");
4550 else if (index->indpred == NIL)
4552 vardata->statsTuple =
4553 SearchSysCache3(STATRELATTINH,
4554 ObjectIdGetDatum(index->indexoid),
4555 Int16GetDatum(pos + 1),
4556 BoolGetDatum(false));
4557 vardata->freefunc = ReleaseSysCache;
4559 if (vardata->statsTuple)
4562 indexpr_item = lnext(indexpr_item);
4565 if (vardata->statsTuple)
4572 * examine_simple_variable
4573 * Handle a simple Var for examine_variable
4575 * This is split out as a subroutine so that we can recurse to deal with
4576 * Vars referencing subqueries.
4578 * We already filled in all the fields of *vardata except for the stats tuple.
4581 examine_simple_variable(PlannerInfo *root, Var *var,
4582 VariableStatData *vardata)
4584 RangeTblEntry *rte = root->simple_rte_array[var->varno];
4586 Assert(IsA(rte, RangeTblEntry));
4588 if (get_relation_stats_hook &&
4589 (*get_relation_stats_hook) (root, rte, var->varattno, vardata))
4592 * The hook took control of acquiring a stats tuple. If it did supply
4593 * a tuple, it'd better have supplied a freefunc.
4595 if (HeapTupleIsValid(vardata->statsTuple) &&
4597 elog(ERROR, "no function provided to release variable stats with");
4599 else if (rte->rtekind == RTE_RELATION)
4602 * Plain table or parent of an inheritance appendrel, so look up the
4603 * column in pg_statistic
4605 vardata->statsTuple = SearchSysCache3(STATRELATTINH,
4606 ObjectIdGetDatum(rte->relid),
4607 Int16GetDatum(var->varattno),
4608 BoolGetDatum(rte->inh));
4609 vardata->freefunc = ReleaseSysCache;
4611 else if (rte->rtekind == RTE_SUBQUERY && !rte->inh)
4614 * Plain subquery (not one that was converted to an appendrel).
4616 Query *subquery = rte->subquery;
4621 * Punt if it's a whole-row var rather than a plain column reference.
4623 if (var->varattno == InvalidAttrNumber)
4627 * Punt if subquery uses set operations or GROUP BY, as these will
4628 * mash underlying columns' stats beyond recognition. (Set ops are
4629 * particularly nasty; if we forged ahead, we would return stats
4630 * relevant to only the leftmost subselect...) DISTINCT is also
4631 * problematic, but we check that later because there is a possibility
4632 * of learning something even with it.
4634 if (subquery->setOperations ||
4635 subquery->groupClause)
4639 * OK, fetch RelOptInfo for subquery. Note that we don't change the
4640 * rel returned in vardata, since caller expects it to be a rel of the
4641 * caller's query level. Because we might already be recursing, we
4642 * can't use that rel pointer either, but have to look up the Var's
4645 rel = find_base_rel(root, var->varno);
4647 /* If the subquery hasn't been planned yet, we have to punt */
4648 if (rel->subroot == NULL)
4650 Assert(IsA(rel->subroot, PlannerInfo));
4653 * Switch our attention to the subquery as mangled by the planner. It
4654 * was okay to look at the pre-planning version for the tests above,
4655 * but now we need a Var that will refer to the subroot's live
4656 * RelOptInfos. For instance, if any subquery pullup happened during
4657 * planning, Vars in the targetlist might have gotten replaced, and we
4658 * need to see the replacement expressions.
4660 subquery = rel->subroot->parse;
4661 Assert(IsA(subquery, Query));
4663 /* Get the subquery output expression referenced by the upper Var */
4664 ste = get_tle_by_resno(subquery->targetList, var->varattno);
4665 if (ste == NULL || ste->resjunk)
4666 elog(ERROR, "subquery %s does not have attribute %d",
4667 rte->eref->aliasname, var->varattno);
4668 var = (Var *) ste->expr;
4671 * If subquery uses DISTINCT, we can't make use of any stats for the
4672 * variable ... but, if it's the only DISTINCT column, we are entitled
4673 * to consider it unique. We do the test this way so that it works
4674 * for cases involving DISTINCT ON.
4676 if (subquery->distinctClause)
4678 if (list_length(subquery->distinctClause) == 1 &&
4679 targetIsInSortList(ste, InvalidOid, subquery->distinctClause))
4680 vardata->isunique = true;
4681 /* cannot go further */
4686 * If the sub-query originated from a view with the security_barrier
4687 * attribute, we must not look at the variable's statistics, though it
4688 * seems all right to notice the existence of a DISTINCT clause. So
4691 * This is probably a harsher restriction than necessary; it's
4692 * certainly OK for the selectivity estimator (which is a C function,
4693 * and therefore omnipotent anyway) to look at the statistics. But
4694 * many selectivity estimators will happily *invoke the operator
4695 * function* to try to work out a good estimate - and that's not OK.
4696 * So for now, don't dig down for stats.
4698 if (rte->security_barrier)
4701 /* Can only handle a simple Var of subquery's query level */
4702 if (var && IsA(var, Var) &&
4703 var->varlevelsup == 0)
4706 * OK, recurse into the subquery. Note that the original setting
4707 * of vardata->isunique (which will surely be false) is left
4708 * unchanged in this situation. That's what we want, since even
4709 * if the underlying column is unique, the subquery may have
4710 * joined to other tables in a way that creates duplicates.
4712 examine_simple_variable(rel->subroot, var, vardata);
4718 * Otherwise, the Var comes from a FUNCTION, VALUES, or CTE RTE. (We
4719 * won't see RTE_JOIN here because join alias Vars have already been
4720 * flattened.) There's not much we can do with function outputs, but
4721 * maybe someday try to be smarter about VALUES and/or CTEs.
4727 * get_variable_numdistinct
4728 * Estimate the number of distinct values of a variable.
4730 * vardata: results of examine_variable
4731 * *isdefault: set to TRUE if the result is a default rather than based on
4732 * anything meaningful.
4734 * NB: be careful to produce a positive integral result, since callers may
4735 * compare the result to exact integer counts, or might divide by it.
4738 get_variable_numdistinct(VariableStatData *vardata, bool *isdefault)
4741 double stanullfrac = 0.0;
4747 * Determine the stadistinct value to use. There are cases where we can
4748 * get an estimate even without a pg_statistic entry, or can get a better
4749 * value than is in pg_statistic. Grab stanullfrac too if we can find it
4750 * (otherwise, assume no nulls, for lack of any better idea).
4752 if (HeapTupleIsValid(vardata->statsTuple))
4754 /* Use the pg_statistic entry */
4755 Form_pg_statistic stats;
4757 stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
4758 stadistinct = stats->stadistinct;
4759 stanullfrac = stats->stanullfrac;
4761 else if (vardata->vartype == BOOLOID)
4764 * Special-case boolean columns: presumably, two distinct values.
4766 * Are there any other datatypes we should wire in special estimates
4774 * We don't keep statistics for system columns, but in some cases we
4775 * can infer distinctness anyway.
4777 if (vardata->var && IsA(vardata->var, Var))
4779 switch (((Var *) vardata->var)->varattno)
4781 case ObjectIdAttributeNumber:
4782 case SelfItemPointerAttributeNumber:
4783 stadistinct = -1.0; /* unique (and all non null) */
4785 case TableOidAttributeNumber:
4786 stadistinct = 1.0; /* only 1 value */
4789 stadistinct = 0.0; /* means "unknown" */
4794 stadistinct = 0.0; /* means "unknown" */
4797 * XXX consider using estimate_num_groups on expressions?
4802 * If there is a unique index or DISTINCT clause for the variable, assume
4803 * it is unique no matter what pg_statistic says; the statistics could be
4804 * out of date, or we might have found a partial unique index that proves
4805 * the var is unique for this query. However, we'd better still believe
4806 * the null-fraction statistic.
4808 if (vardata->isunique)
4809 stadistinct = -1.0 * (1.0 - stanullfrac);
4812 * If we had an absolute estimate, use that.
4814 if (stadistinct > 0.0)
4815 return clamp_row_est(stadistinct);
4818 * Otherwise we need to get the relation size; punt if not available.
4820 if (vardata->rel == NULL)
4823 return DEFAULT_NUM_DISTINCT;
4825 ntuples = vardata->rel->tuples;
4829 return DEFAULT_NUM_DISTINCT;
4833 * If we had a relative estimate, use that.
4835 if (stadistinct < 0.0)
4836 return clamp_row_est(-stadistinct * ntuples);
4839 * With no data, estimate ndistinct = ntuples if the table is small, else
4840 * use default. We use DEFAULT_NUM_DISTINCT as the cutoff for "small" so
4841 * that the behavior isn't discontinuous.
4843 if (ntuples < DEFAULT_NUM_DISTINCT)
4844 return clamp_row_est(ntuples);
4847 return DEFAULT_NUM_DISTINCT;
4851 * get_variable_range
4852 * Estimate the minimum and maximum value of the specified variable.
4853 * If successful, store values in *min and *max, and return TRUE.
4854 * If no data available, return FALSE.
4856 * sortop is the "<" comparison operator to use. This should generally
4857 * be "<" not ">", as only the former is likely to be found in pg_statistic.
4860 get_variable_range(PlannerInfo *root, VariableStatData *vardata, Oid sortop,
4861 Datum *min, Datum *max)
4865 bool have_data = false;
4873 * XXX It's very tempting to try to use the actual column min and max, if
4874 * we can get them relatively-cheaply with an index probe. However, since
4875 * this function is called many times during join planning, that could
4876 * have unpleasant effects on planning speed. Need more investigation
4877 * before enabling this.
4880 if (get_actual_variable_range(root, vardata, sortop, min, max))
4884 if (!HeapTupleIsValid(vardata->statsTuple))
4886 /* no stats available, so default result */
4890 get_typlenbyval(vardata->atttype, &typLen, &typByVal);
4893 * If there is a histogram, grab the first and last values.
4895 * If there is a histogram that is sorted with some other operator than
4896 * the one we want, fail --- this suggests that there is data we can't
4899 if (get_attstatsslot(vardata->statsTuple,
4900 vardata->atttype, vardata->atttypmod,
4901 STATISTIC_KIND_HISTOGRAM, sortop,
4908 tmin = datumCopy(values[0], typByVal, typLen);
4909 tmax = datumCopy(values[nvalues - 1], typByVal, typLen);
4912 free_attstatsslot(vardata->atttype, values, nvalues, NULL, 0);
4914 else if (get_attstatsslot(vardata->statsTuple,
4915 vardata->atttype, vardata->atttypmod,
4916 STATISTIC_KIND_HISTOGRAM, InvalidOid,
4921 free_attstatsslot(vardata->atttype, values, nvalues, NULL, 0);
4926 * If we have most-common-values info, look for extreme MCVs. This is
4927 * needed even if we also have a histogram, since the histogram excludes
4928 * the MCVs. However, usually the MCVs will not be the extreme values, so
4929 * avoid unnecessary data copying.
4931 if (get_attstatsslot(vardata->statsTuple,
4932 vardata->atttype, vardata->atttypmod,
4933 STATISTIC_KIND_MCV, InvalidOid,
4938 bool tmin_is_mcv = false;
4939 bool tmax_is_mcv = false;
4942 fmgr_info(get_opcode(sortop), &opproc);
4944 for (i = 0; i < nvalues; i++)
4948 tmin = tmax = values[i];
4949 tmin_is_mcv = tmax_is_mcv = have_data = true;
4952 if (DatumGetBool(FunctionCall2Coll(&opproc,
4953 DEFAULT_COLLATION_OID,
4959 if (DatumGetBool(FunctionCall2Coll(&opproc,
4960 DEFAULT_COLLATION_OID,
4968 tmin = datumCopy(tmin, typByVal, typLen);
4970 tmax = datumCopy(tmax, typByVal, typLen);
4971 free_attstatsslot(vardata->atttype, values, nvalues, NULL, 0);
4981 * get_actual_variable_range
4982 * Attempt to identify the current *actual* minimum and/or maximum
4983 * of the specified variable, by looking for a suitable btree index
4984 * and fetching its low and/or high values.
4985 * If successful, store values in *min and *max, and return TRUE.
4986 * (Either pointer can be NULL if that endpoint isn't needed.)
4987 * If no data available, return FALSE.
4989 * sortop is the "<" comparison operator to use.
4992 get_actual_variable_range(PlannerInfo *root, VariableStatData *vardata,
4994 Datum *min, Datum *max)
4996 bool have_data = false;
4997 RelOptInfo *rel = vardata->rel;
5001 /* No hope if no relation or it doesn't have indexes */
5002 if (rel == NULL || rel->indexlist == NIL)
5004 /* If it has indexes it must be a plain relation */
5005 rte = root->simple_rte_array[rel->relid];
5006 Assert(rte->rtekind == RTE_RELATION);
5008 /* Search through the indexes to see if any match our problem */
5009 foreach(lc, rel->indexlist)
5011 IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
5012 ScanDirection indexscandir;
5014 /* Ignore non-btree indexes */
5015 if (index->relam != BTREE_AM_OID)
5019 * Ignore partial indexes --- we only want stats that cover the entire
5022 if (index->indpred != NIL)
5026 * The index list might include hypothetical indexes inserted by a
5027 * get_relation_info hook --- don't try to access them.
5029 if (index->hypothetical)
5033 * The first index column must match the desired variable and sort
5034 * operator --- but we can use a descending-order index.
5036 if (!match_index_to_operand(vardata->var, 0, index))
5038 switch (get_op_opfamily_strategy(sortop, index->sortopfamily[0]))
5040 case BTLessStrategyNumber:
5041 if (index->reverse_sort[0])
5042 indexscandir = BackwardScanDirection;
5044 indexscandir = ForwardScanDirection;
5046 case BTGreaterStrategyNumber:
5047 if (index->reverse_sort[0])
5048 indexscandir = ForwardScanDirection;
5050 indexscandir = BackwardScanDirection;
5053 /* index doesn't match the sortop */
5058 * Found a suitable index to extract data from. We'll need an EState
5059 * and a bunch of other infrastructure.
5063 ExprContext *econtext;
5064 MemoryContext tmpcontext;
5065 MemoryContext oldcontext;
5068 IndexInfo *indexInfo;
5069 TupleTableSlot *slot;
5072 ScanKeyData scankeys[1];
5073 IndexScanDesc index_scan;
5075 Datum values[INDEX_MAX_KEYS];
5076 bool isnull[INDEX_MAX_KEYS];
5077 SnapshotData SnapshotDirty;
5079 estate = CreateExecutorState();
5080 econtext = GetPerTupleExprContext(estate);
5081 /* Make sure any cruft is generated in the econtext's memory */
5082 tmpcontext = econtext->ecxt_per_tuple_memory;
5083 oldcontext = MemoryContextSwitchTo(tmpcontext);
5086 * Open the table and index so we can read from them. We should
5087 * already have at least AccessShareLock on the table, but not
5088 * necessarily on the index.
5090 heapRel = heap_open(rte->relid, NoLock);
5091 indexRel = index_open(index->indexoid, AccessShareLock);
5093 /* extract index key information from the index's pg_index info */
5094 indexInfo = BuildIndexInfo(indexRel);
5096 /* some other stuff */
5097 slot = MakeSingleTupleTableSlot(RelationGetDescr(heapRel));
5098 econtext->ecxt_scantuple = slot;
5099 get_typlenbyval(vardata->atttype, &typLen, &typByVal);
5100 InitDirtySnapshot(SnapshotDirty);
5102 /* set up an IS NOT NULL scan key so that we ignore nulls */
5103 ScanKeyEntryInitialize(&scankeys[0],
5104 SK_ISNULL | SK_SEARCHNOTNULL,
5105 1, /* index col to scan */
5106 InvalidStrategy, /* no strategy */
5107 InvalidOid, /* no strategy subtype */
5108 InvalidOid, /* no collation */
5109 InvalidOid, /* no reg proc for this */
5110 (Datum) 0); /* constant */
5114 /* If min is requested ... */
5118 * In principle, we should scan the index with our current
5119 * active snapshot, which is the best approximation we've got
5120 * to what the query will see when executed. But that won't
5121 * be exact if a new snap is taken before running the query,
5122 * and it can be very expensive if a lot of uncommitted rows
5123 * exist at the end of the index (because we'll laboriously
5124 * fetch each one and reject it). What seems like a good
5125 * compromise is to use SnapshotDirty. That will accept
5126 * uncommitted rows, and thus avoid fetching multiple heap
5127 * tuples in this scenario. On the other hand, it will reject
5128 * known-dead rows, and thus not give a bogus answer when the
5129 * extreme value has been deleted; that case motivates not
5130 * using SnapshotAny here.
5132 index_scan = index_beginscan(heapRel, indexRel, &SnapshotDirty,
5134 index_rescan(index_scan, scankeys, 1, NULL, 0);
5136 /* Fetch first tuple in sortop's direction */
5137 if ((tup = index_getnext(index_scan,
5138 indexscandir)) != NULL)
5140 /* Extract the index column values from the heap tuple */
5141 ExecStoreTuple(tup, slot, InvalidBuffer, false);
5142 FormIndexDatum(indexInfo, slot, estate,
5145 /* Shouldn't have got a null, but be careful */
5147 elog(ERROR, "found unexpected null value in index \"%s\"",
5148 RelationGetRelationName(indexRel));
5150 /* Copy the index column value out to caller's context */
5151 MemoryContextSwitchTo(oldcontext);
5152 *min = datumCopy(values[0], typByVal, typLen);
5153 MemoryContextSwitchTo(tmpcontext);
5158 index_endscan(index_scan);
5161 /* If max is requested, and we didn't find the index is empty */
5162 if (max && have_data)
5164 index_scan = index_beginscan(heapRel, indexRel, &SnapshotDirty,
5166 index_rescan(index_scan, scankeys, 1, NULL, 0);
5168 /* Fetch first tuple in reverse direction */
5169 if ((tup = index_getnext(index_scan,
5170 -indexscandir)) != NULL)
5172 /* Extract the index column values from the heap tuple */
5173 ExecStoreTuple(tup, slot, InvalidBuffer, false);
5174 FormIndexDatum(indexInfo, slot, estate,
5177 /* Shouldn't have got a null, but be careful */
5179 elog(ERROR, "found unexpected null value in index \"%s\"",
5180 RelationGetRelationName(indexRel));
5182 /* Copy the index column value out to caller's context */
5183 MemoryContextSwitchTo(oldcontext);
5184 *max = datumCopy(values[0], typByVal, typLen);
5185 MemoryContextSwitchTo(tmpcontext);
5190 index_endscan(index_scan);
5193 /* Clean everything up */
5194 ExecDropSingleTupleTableSlot(slot);
5196 index_close(indexRel, AccessShareLock);
5197 heap_close(heapRel, NoLock);
5199 MemoryContextSwitchTo(oldcontext);
5200 FreeExecutorState(estate);
5202 /* And we're done */
5211 * find_join_input_rel
5212 * Look up the input relation for a join.
5214 * We assume that the input relation's RelOptInfo must have been constructed
5218 find_join_input_rel(PlannerInfo *root, Relids relids)
5220 RelOptInfo *rel = NULL;
5222 switch (bms_membership(relids))
5225 /* should not happen */
5228 rel = find_base_rel(root, bms_singleton_member(relids));
5231 rel = find_join_rel(root, relids);
5236 elog(ERROR, "could not find RelOptInfo for given relids");
5242 /*-------------------------------------------------------------------------
5244 * Pattern analysis functions
5246 * These routines support analysis of LIKE and regular-expression patterns
5247 * by the planner/optimizer. It's important that they agree with the
5248 * regular-expression code in backend/regex/ and the LIKE code in
5249 * backend/utils/adt/like.c. Also, the computation of the fixed prefix
5250 * must be conservative: if we report a string longer than the true fixed
5251 * prefix, the query may produce actually wrong answers, rather than just
5252 * getting a bad selectivity estimate!
5254 * Note that the prefix-analysis functions are called from
5255 * backend/optimizer/path/indxpath.c as well as from routines in this file.
5257 *-------------------------------------------------------------------------
5261 * Check whether char is a letter (and, hence, subject to case-folding)
5263 * In multibyte character sets, we can't use isalpha, and it does not seem
5264 * worth trying to convert to wchar_t to use iswalpha. Instead, just assume
5265 * any multibyte char is potentially case-varying.
5268 pattern_char_isalpha(char c, bool is_multibyte,
5269 pg_locale_t locale, bool locale_is_c)
5272 return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
5273 else if (is_multibyte && IS_HIGHBIT_SET(c))
5275 #ifdef HAVE_LOCALE_T
5277 return isalpha_l((unsigned char) c, locale);
5280 return isalpha((unsigned char) c);
5284 * Extract the fixed prefix, if any, for a pattern.
5286 * *prefix is set to a palloc'd prefix string (in the form of a Const node),
5287 * or to NULL if no fixed prefix exists for the pattern.
5288 * If rest_selec is not NULL, *rest_selec is set to an estimate of the
5289 * selectivity of the remainder of the pattern (without any fixed prefix).
5290 * The prefix Const has the same type (TEXT or BYTEA) as the input pattern.
5292 * The return value distinguishes no fixed prefix, a partial prefix,
5293 * or an exact-match-only pattern.
5296 static Pattern_Prefix_Status
5297 like_fixed_prefix(Const *patt_const, bool case_insensitive, Oid collation,
5298 Const **prefix_const, Selectivity *rest_selec)
5303 Oid typeid = patt_const->consttype;
5306 bool is_multibyte = (pg_database_encoding_max_length() > 1);
5307 pg_locale_t locale = 0;
5308 bool locale_is_c = false;
5310 /* the right-hand const is type text or bytea */
5311 Assert(typeid == BYTEAOID || typeid == TEXTOID);
5313 if (case_insensitive)
5315 if (typeid == BYTEAOID)
5317 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
5318 errmsg("case insensitive matching not supported on type bytea")));
5320 /* If case-insensitive, we need locale info */
5321 if (lc_ctype_is_c(collation))
5323 else if (collation != DEFAULT_COLLATION_OID)
5325 if (!OidIsValid(collation))
5328 * This typically means that the parser could not resolve a
5329 * conflict of implicit collations, so report it that way.
5332 (errcode(ERRCODE_INDETERMINATE_COLLATION),
5333 errmsg("could not determine which collation to use for ILIKE"),
5334 errhint("Use the COLLATE clause to set the collation explicitly.")));
5336 locale = pg_newlocale_from_collation(collation);
5340 if (typeid != BYTEAOID)
5342 patt = TextDatumGetCString(patt_const->constvalue);
5343 pattlen = strlen(patt);
5347 bytea *bstr = DatumGetByteaP(patt_const->constvalue);
5349 pattlen = VARSIZE(bstr) - VARHDRSZ;
5350 patt = (char *) palloc(pattlen);
5351 memcpy(patt, VARDATA(bstr), pattlen);
5352 if ((Pointer) bstr != DatumGetPointer(patt_const->constvalue))
5356 match = palloc(pattlen + 1);
5358 for (pos = 0; pos < pattlen; pos++)
5360 /* % and _ are wildcard characters in LIKE */
5361 if (patt[pos] == '%' ||
5365 /* Backslash escapes the next character */
5366 if (patt[pos] == '\\')
5373 /* Stop if case-varying character (it's sort of a wildcard) */
5374 if (case_insensitive &&
5375 pattern_char_isalpha(patt[pos], is_multibyte, locale, locale_is_c))
5378 match[match_pos++] = patt[pos];
5381 match[match_pos] = '\0';
5383 if (typeid != BYTEAOID)
5384 *prefix_const = string_to_const(match, typeid);
5386 *prefix_const = string_to_bytea_const(match, match_pos);
5388 if (rest_selec != NULL)
5389 *rest_selec = like_selectivity(&patt[pos], pattlen - pos,
5395 /* in LIKE, an empty pattern is an exact match! */
5397 return Pattern_Prefix_Exact; /* reached end of pattern, so exact */
5400 return Pattern_Prefix_Partial;
5402 return Pattern_Prefix_None;
5405 static Pattern_Prefix_Status
5406 regex_fixed_prefix(Const *patt_const, bool case_insensitive, Oid collation,
5407 Const **prefix_const, Selectivity *rest_selec)
5409 Oid typeid = patt_const->consttype;
5414 * Should be unnecessary, there are no bytea regex operators defined. As
5415 * such, it should be noted that the rest of this function has *not* been
5416 * made safe for binary (possibly NULL containing) strings.
5418 if (typeid == BYTEAOID)
5420 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
5421 errmsg("regular-expression matching not supported on type bytea")));
5423 /* Use the regexp machinery to extract the prefix, if any */
5424 prefix = regexp_fixed_prefix(DatumGetTextPP(patt_const->constvalue),
5425 case_insensitive, collation,
5430 *prefix_const = NULL;
5432 if (rest_selec != NULL)
5434 char *patt = TextDatumGetCString(patt_const->constvalue);
5436 *rest_selec = regex_selectivity(patt, strlen(patt),
5442 return Pattern_Prefix_None;
5445 *prefix_const = string_to_const(prefix, typeid);
5447 if (rest_selec != NULL)
5451 /* Exact match, so there's no additional selectivity */
5456 char *patt = TextDatumGetCString(patt_const->constvalue);
5458 *rest_selec = regex_selectivity(patt, strlen(patt),
5468 return Pattern_Prefix_Exact; /* pattern specifies exact match */
5470 return Pattern_Prefix_Partial;
5473 Pattern_Prefix_Status
5474 pattern_fixed_prefix(Const *patt, Pattern_Type ptype, Oid collation,
5475 Const **prefix, Selectivity *rest_selec)
5477 Pattern_Prefix_Status result;
5481 case Pattern_Type_Like:
5482 result = like_fixed_prefix(patt, false, collation,
5483 prefix, rest_selec);
5485 case Pattern_Type_Like_IC:
5486 result = like_fixed_prefix(patt, true, collation,
5487 prefix, rest_selec);
5489 case Pattern_Type_Regex:
5490 result = regex_fixed_prefix(patt, false, collation,
5491 prefix, rest_selec);
5493 case Pattern_Type_Regex_IC:
5494 result = regex_fixed_prefix(patt, true, collation,
5495 prefix, rest_selec);
5498 elog(ERROR, "unrecognized ptype: %d", (int) ptype);
5499 result = Pattern_Prefix_None; /* keep compiler quiet */
5506 * Estimate the selectivity of a fixed prefix for a pattern match.
5508 * A fixed prefix "foo" is estimated as the selectivity of the expression
5509 * "variable >= 'foo' AND variable < 'fop'" (see also indxpath.c).
5511 * The selectivity estimate is with respect to the portion of the column
5512 * population represented by the histogram --- the caller must fold this
5513 * together with info about MCVs and NULLs.
5515 * We use the >= and < operators from the specified btree opfamily to do the
5516 * estimation. The given variable and Const must be of the associated
5519 * XXX Note: we make use of the upper bound to estimate operator selectivity
5520 * even if the locale is such that we cannot rely on the upper-bound string.
5521 * The selectivity only needs to be approximately right anyway, so it seems
5522 * more useful to use the upper-bound code than not.
5525 prefix_selectivity(PlannerInfo *root, VariableStatData *vardata,
5526 Oid vartype, Oid opfamily, Const *prefixcon)
5528 Selectivity prefixsel;
5531 Const *greaterstrcon;
5534 cmpopr = get_opfamily_member(opfamily, vartype, vartype,
5535 BTGreaterEqualStrategyNumber);
5536 if (cmpopr == InvalidOid)
5537 elog(ERROR, "no >= operator for opfamily %u", opfamily);
5538 fmgr_info(get_opcode(cmpopr), &opproc);
5540 prefixsel = ineq_histogram_selectivity(root, vardata, &opproc, true,
5541 prefixcon->constvalue,
5542 prefixcon->consttype);
5544 if (prefixsel < 0.0)
5546 /* No histogram is present ... return a suitable default estimate */
5547 return DEFAULT_MATCH_SEL;
5551 * If we can create a string larger than the prefix, say
5555 cmpopr = get_opfamily_member(opfamily, vartype, vartype,
5556 BTLessStrategyNumber);
5557 if (cmpopr == InvalidOid)
5558 elog(ERROR, "no < operator for opfamily %u", opfamily);
5559 fmgr_info(get_opcode(cmpopr), &opproc);
5560 greaterstrcon = make_greater_string(prefixcon, &opproc,
5561 DEFAULT_COLLATION_OID);
5566 topsel = ineq_histogram_selectivity(root, vardata, &opproc, false,
5567 greaterstrcon->constvalue,
5568 greaterstrcon->consttype);
5570 /* ineq_histogram_selectivity worked before, it shouldn't fail now */
5571 Assert(topsel >= 0.0);
5574 * Merge the two selectivities in the same way as for a range query
5575 * (see clauselist_selectivity()). Note that we don't need to worry
5576 * about double-exclusion of nulls, since ineq_histogram_selectivity
5577 * doesn't count those anyway.
5579 prefixsel = topsel + prefixsel - 1.0;
5583 * If the prefix is long then the two bounding values might be too close
5584 * together for the histogram to distinguish them usefully, resulting in a
5585 * zero estimate (plus or minus roundoff error). To avoid returning a
5586 * ridiculously small estimate, compute the estimated selectivity for
5587 * "variable = 'foo'", and clamp to that. (Obviously, the resultant
5588 * estimate should be at least that.)
5590 * We apply this even if we couldn't make a greater string. That case
5591 * suggests that the prefix is near the maximum possible, and thus
5592 * probably off the end of the histogram, and thus we probably got a very
5593 * small estimate from the >= condition; so we still need to clamp.
5595 cmpopr = get_opfamily_member(opfamily, vartype, vartype,
5596 BTEqualStrategyNumber);
5597 if (cmpopr == InvalidOid)
5598 elog(ERROR, "no = operator for opfamily %u", opfamily);
5599 eq_sel = var_eq_const(vardata, cmpopr, prefixcon->constvalue,
5602 prefixsel = Max(prefixsel, eq_sel);
5609 * Estimate the selectivity of a pattern of the specified type.
5610 * Note that any fixed prefix of the pattern will have been removed already,
5611 * so actually we may be looking at just a fragment of the pattern.
5613 * For now, we use a very simplistic approach: fixed characters reduce the
5614 * selectivity a good deal, character ranges reduce it a little,
5615 * wildcards (such as % for LIKE or .* for regex) increase it.
5618 #define FIXED_CHAR_SEL 0.20 /* about 1/5 */
5619 #define CHAR_RANGE_SEL 0.25
5620 #define ANY_CHAR_SEL 0.9 /* not 1, since it won't match end-of-string */
5621 #define FULL_WILDCARD_SEL 5.0
5622 #define PARTIAL_WILDCARD_SEL 2.0
5625 like_selectivity(const char *patt, int pattlen, bool case_insensitive)
5627 Selectivity sel = 1.0;
5630 /* Skip any leading wildcard; it's already factored into initial sel */
5631 for (pos = 0; pos < pattlen; pos++)
5633 if (patt[pos] != '%' && patt[pos] != '_')
5637 for (; pos < pattlen; pos++)
5639 /* % and _ are wildcard characters in LIKE */
5640 if (patt[pos] == '%')
5641 sel *= FULL_WILDCARD_SEL;
5642 else if (patt[pos] == '_')
5643 sel *= ANY_CHAR_SEL;
5644 else if (patt[pos] == '\\')
5646 /* Backslash quotes the next character */
5650 sel *= FIXED_CHAR_SEL;
5653 sel *= FIXED_CHAR_SEL;
5655 /* Could get sel > 1 if multiple wildcards */
5662 regex_selectivity_sub(const char *patt, int pattlen, bool case_insensitive)
5664 Selectivity sel = 1.0;
5665 int paren_depth = 0;
5666 int paren_pos = 0; /* dummy init to keep compiler quiet */
5669 for (pos = 0; pos < pattlen; pos++)
5671 if (patt[pos] == '(')
5673 if (paren_depth == 0)
5674 paren_pos = pos; /* remember start of parenthesized item */
5677 else if (patt[pos] == ')' && paren_depth > 0)
5680 if (paren_depth == 0)
5681 sel *= regex_selectivity_sub(patt + (paren_pos + 1),
5682 pos - (paren_pos + 1),
5685 else if (patt[pos] == '|' && paren_depth == 0)
5688 * If unquoted | is present at paren level 0 in pattern, we have
5689 * multiple alternatives; sum their probabilities.
5691 sel += regex_selectivity_sub(patt + (pos + 1),
5692 pattlen - (pos + 1),
5694 break; /* rest of pattern is now processed */
5696 else if (patt[pos] == '[')
5698 bool negclass = false;
5700 if (patt[++pos] == '^')
5705 if (patt[pos] == ']') /* ']' at start of class is not
5708 while (pos < pattlen && patt[pos] != ']')
5710 if (paren_depth == 0)
5711 sel *= (negclass ? (1.0 - CHAR_RANGE_SEL) : CHAR_RANGE_SEL);
5713 else if (patt[pos] == '.')
5715 if (paren_depth == 0)
5716 sel *= ANY_CHAR_SEL;
5718 else if (patt[pos] == '*' ||
5722 /* Ought to be smarter about quantifiers... */
5723 if (paren_depth == 0)
5724 sel *= PARTIAL_WILDCARD_SEL;
5726 else if (patt[pos] == '{')
5728 while (pos < pattlen && patt[pos] != '}')
5730 if (paren_depth == 0)
5731 sel *= PARTIAL_WILDCARD_SEL;
5733 else if (patt[pos] == '\\')
5735 /* backslash quotes the next character */
5739 if (paren_depth == 0)
5740 sel *= FIXED_CHAR_SEL;
5744 if (paren_depth == 0)
5745 sel *= FIXED_CHAR_SEL;
5748 /* Could get sel > 1 if multiple wildcards */
5755 regex_selectivity(const char *patt, int pattlen, bool case_insensitive,
5756 int fixed_prefix_len)
5760 /* If patt doesn't end with $, consider it to have a trailing wildcard */
5761 if (pattlen > 0 && patt[pattlen - 1] == '$' &&
5762 (pattlen == 1 || patt[pattlen - 2] != '\\'))
5764 /* has trailing $ */
5765 sel = regex_selectivity_sub(patt, pattlen - 1, case_insensitive);
5770 sel = regex_selectivity_sub(patt, pattlen, case_insensitive);
5771 sel *= FULL_WILDCARD_SEL;
5774 /* If there's a fixed prefix, discount its selectivity */
5775 if (fixed_prefix_len > 0)
5776 sel /= pow(FIXED_CHAR_SEL, fixed_prefix_len);
5778 /* Make sure result stays in range */
5779 CLAMP_PROBABILITY(sel);
5785 * For bytea, the increment function need only increment the current byte
5786 * (there are no multibyte characters to worry about).
5789 byte_increment(unsigned char *ptr, int len)
5798 * Try to generate a string greater than the given string or any
5799 * string it is a prefix of. If successful, return a palloc'd string
5800 * in the form of a Const node; else return NULL.
5802 * The caller must provide the appropriate "less than" comparison function
5803 * for testing the strings, along with the collation to use.
5805 * The key requirement here is that given a prefix string, say "foo",
5806 * we must be able to generate another string "fop" that is greater than
5807 * all strings "foobar" starting with "foo". We can test that we have
5808 * generated a string greater than the prefix string, but in non-C collations
5809 * that is not a bulletproof guarantee that an extension of the string might
5810 * not sort after it; an example is that "foo " is less than "foo!", but it
5811 * is not clear that a "dictionary" sort ordering will consider "foo!" less
5812 * than "foo bar". CAUTION: Therefore, this function should be used only for
5813 * estimation purposes when working in a non-C collation.
5815 * To try to catch most cases where an extended string might otherwise sort
5816 * before the result value, we determine which of the strings "Z", "z", "y",
5817 * and "9" is seen as largest by the collation, and append that to the given
5818 * prefix before trying to find a string that compares as larger.
5820 * To search for a greater string, we repeatedly "increment" the rightmost
5821 * character, using an encoding-specific character incrementer function.
5822 * When it's no longer possible to increment the last character, we truncate
5823 * off that character and start incrementing the next-to-rightmost.
5824 * For example, if "z" were the last character in the sort order, then we
5825 * could produce "foo" as a string greater than "fonz".
5827 * This could be rather slow in the worst case, but in most cases we
5828 * won't have to try more than one or two strings before succeeding.
5830 * Note that it's important for the character incrementer not to be too anal
5831 * about producing every possible character code, since in some cases the only
5832 * way to get a larger string is to increment a previous character position.
5833 * So we don't want to spend too much time trying every possible character
5834 * code at the last position. A good rule of thumb is to be sure that we
5835 * don't try more than 256*K values for a K-byte character (and definitely
5836 * not 256^K, which is what an exhaustive search would approach).
5839 make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)
5841 Oid datatype = str_const->consttype;
5845 text *cmptxt = NULL;
5846 mbcharacter_incrementer charinc;
5849 * Get a modifiable copy of the prefix string in C-string format, and set
5850 * up the string we will compare to as a Datum. In C locale this can just
5851 * be the given prefix string, otherwise we need to add a suffix. Types
5852 * NAME and BYTEA sort bytewise so they don't need a suffix either.
5854 if (datatype == NAMEOID)
5856 workstr = DatumGetCString(DirectFunctionCall1(nameout,
5857 str_const->constvalue));
5858 len = strlen(workstr);
5859 cmpstr = str_const->constvalue;
5861 else if (datatype == BYTEAOID)
5863 bytea *bstr = DatumGetByteaP(str_const->constvalue);
5865 len = VARSIZE(bstr) - VARHDRSZ;
5866 workstr = (char *) palloc(len);
5867 memcpy(workstr, VARDATA(bstr), len);
5868 if ((Pointer) bstr != DatumGetPointer(str_const->constvalue))
5870 cmpstr = str_const->constvalue;
5874 workstr = TextDatumGetCString(str_const->constvalue);
5875 len = strlen(workstr);
5876 if (lc_collate_is_c(collation) || len == 0)
5877 cmpstr = str_const->constvalue;
5880 /* If first time through, determine the suffix to use */
5881 static char suffixchar = 0;
5882 static Oid suffixcollation = 0;
5884 if (!suffixchar || suffixcollation != collation)
5889 if (varstr_cmp(best, 1, "z", 1, collation) < 0)
5891 if (varstr_cmp(best, 1, "y", 1, collation) < 0)
5893 if (varstr_cmp(best, 1, "9", 1, collation) < 0)
5896 suffixcollation = collation;
5899 /* And build the string to compare to */
5900 cmptxt = (text *) palloc(VARHDRSZ + len + 1);
5901 SET_VARSIZE(cmptxt, VARHDRSZ + len + 1);
5902 memcpy(VARDATA(cmptxt), workstr, len);
5903 *(VARDATA(cmptxt) + len) = suffixchar;
5904 cmpstr = PointerGetDatum(cmptxt);
5908 /* Select appropriate character-incrementer function */
5909 if (datatype == BYTEAOID)
5910 charinc = byte_increment;
5912 charinc = pg_database_encoding_character_incrementer();
5914 /* And search ... */
5918 unsigned char *lastchar;
5920 /* Identify the last character --- for bytea, just the last byte */
5921 if (datatype == BYTEAOID)
5924 charlen = len - pg_mbcliplen(workstr, len, len - 1);
5925 lastchar = (unsigned char *) (workstr + len - charlen);
5928 * Try to generate a larger string by incrementing the last character
5929 * (for BYTEA, we treat each byte as a character).
5931 * Note: the incrementer function is expected to return true if it's
5932 * generated a valid-per-the-encoding new character, otherwise false.
5933 * The contents of the character on false return are unspecified.
5935 while (charinc(lastchar, charlen))
5937 Const *workstr_const;
5939 if (datatype == BYTEAOID)
5940 workstr_const = string_to_bytea_const(workstr, len);
5942 workstr_const = string_to_const(workstr, datatype);
5944 if (DatumGetBool(FunctionCall2Coll(ltproc,
5947 workstr_const->constvalue)))
5949 /* Successfully made a string larger than cmpstr */
5953 return workstr_const;
5956 /* No good, release unusable value and try again */
5957 pfree(DatumGetPointer(workstr_const->constvalue));
5958 pfree(workstr_const);
5962 * No luck here, so truncate off the last character and try to
5963 * increment the next one.
5966 workstr[len] = '\0';
5978 * Generate a Datum of the appropriate type from a C string.
5979 * Note that all of the supported types are pass-by-ref, so the
5980 * returned value should be pfree'd if no longer needed.
5983 string_to_datum(const char *str, Oid datatype)
5985 Assert(str != NULL);
5988 * We cheat a little by assuming that CStringGetTextDatum() will do for
5989 * bpchar and varchar constants too...
5991 if (datatype == NAMEOID)
5992 return DirectFunctionCall1(namein, CStringGetDatum(str));
5993 else if (datatype == BYTEAOID)
5994 return DirectFunctionCall1(byteain, CStringGetDatum(str));
5996 return CStringGetTextDatum(str);
6000 * Generate a Const node of the appropriate type from a C string.
6003 string_to_const(const char *str, Oid datatype)
6005 Datum conval = string_to_datum(str, datatype);
6010 * We only need to support a few datatypes here, so hard-wire properties
6011 * instead of incurring the expense of catalog lookups.
6018 collation = DEFAULT_COLLATION_OID;
6023 collation = InvalidOid;
6024 constlen = NAMEDATALEN;
6028 collation = InvalidOid;
6033 elog(ERROR, "unexpected datatype in string_to_const: %u",
6038 return makeConst(datatype, -1, collation, constlen,
6039 conval, false, false);
6043 * Generate a Const node of bytea type from a binary C string and a length.
6046 string_to_bytea_const(const char *str, size_t str_len)
6048 bytea *bstr = palloc(VARHDRSZ + str_len);
6051 memcpy(VARDATA(bstr), str, str_len);
6052 SET_VARSIZE(bstr, VARHDRSZ + str_len);
6053 conval = PointerGetDatum(bstr);
6055 return makeConst(BYTEAOID, -1, InvalidOid, -1, conval, false, false);
6058 /*-------------------------------------------------------------------------
6060 * Index cost estimation functions
6062 *-------------------------------------------------------------------------
6066 deconstruct_indexquals(IndexPath *path)
6069 IndexOptInfo *index = path->indexinfo;
6073 forboth(lcc, path->indexquals, lci, path->indexqualcols)
6075 RestrictInfo *rinfo = (RestrictInfo *) lfirst(lcc);
6076 int indexcol = lfirst_int(lci);
6080 IndexQualInfo *qinfo;
6082 Assert(IsA(rinfo, RestrictInfo));
6083 clause = rinfo->clause;
6085 qinfo = (IndexQualInfo *) palloc(sizeof(IndexQualInfo));
6086 qinfo->rinfo = rinfo;
6087 qinfo->indexcol = indexcol;
6089 if (IsA(clause, OpExpr))
6091 qinfo->clause_op = ((OpExpr *) clause)->opno;
6092 leftop = get_leftop(clause);
6093 rightop = get_rightop(clause);
6094 if (match_index_to_operand(leftop, indexcol, index))
6096 qinfo->varonleft = true;
6097 qinfo->other_operand = rightop;
6101 Assert(match_index_to_operand(rightop, indexcol, index));
6102 qinfo->varonleft = false;
6103 qinfo->other_operand = leftop;
6106 else if (IsA(clause, RowCompareExpr))
6108 RowCompareExpr *rc = (RowCompareExpr *) clause;
6110 qinfo->clause_op = linitial_oid(rc->opnos);
6111 /* Examine only first columns to determine left/right sides */
6112 if (match_index_to_operand((Node *) linitial(rc->largs),
6115 qinfo->varonleft = true;
6116 qinfo->other_operand = (Node *) rc->rargs;
6120 Assert(match_index_to_operand((Node *) linitial(rc->rargs),
6122 qinfo->varonleft = false;
6123 qinfo->other_operand = (Node *) rc->largs;
6126 else if (IsA(clause, ScalarArrayOpExpr))
6128 ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) clause;
6130 qinfo->clause_op = saop->opno;
6131 /* index column is always on the left in this case */
6132 Assert(match_index_to_operand((Node *) linitial(saop->args),
6134 qinfo->varonleft = true;
6135 qinfo->other_operand = (Node *) lsecond(saop->args);
6137 else if (IsA(clause, NullTest))
6139 qinfo->clause_op = InvalidOid;
6140 Assert(match_index_to_operand((Node *) ((NullTest *) clause)->arg,
6142 qinfo->varonleft = true;
6143 qinfo->other_operand = NULL;
6147 elog(ERROR, "unsupported indexqual type: %d",
6148 (int) nodeTag(clause));
6151 result = lappend(result, qinfo);
6157 * Simple function to compute the total eval cost of the "other operands"
6158 * in an IndexQualInfo list. Since we know these will be evaluated just
6159 * once per scan, there's no need to distinguish startup from per-row cost.
6162 other_operands_eval_cost(PlannerInfo *root, List *qinfos)
6164 Cost qual_arg_cost = 0;
6169 IndexQualInfo *qinfo = (IndexQualInfo *) lfirst(lc);
6170 QualCost index_qual_cost;
6172 cost_qual_eval_node(&index_qual_cost, qinfo->other_operand, root);
6173 qual_arg_cost += index_qual_cost.startup + index_qual_cost.per_tuple;
6175 return qual_arg_cost;
6179 * Get other-operand eval cost for an index orderby list.
6181 * Index orderby expressions aren't represented as RestrictInfos (since they
6182 * aren't boolean, usually). So we can't apply deconstruct_indexquals to
6183 * them. However, they are much simpler to deal with since they are always
6184 * OpExprs and the index column is always on the left.
6187 orderby_operands_eval_cost(PlannerInfo *root, IndexPath *path)
6189 Cost qual_arg_cost = 0;
6192 foreach(lc, path->indexorderbys)
6194 Expr *clause = (Expr *) lfirst(lc);
6195 Node *other_operand;
6196 QualCost index_qual_cost;
6198 if (IsA(clause, OpExpr))
6200 other_operand = get_rightop(clause);
6204 elog(ERROR, "unsupported indexorderby type: %d",
6205 (int) nodeTag(clause));
6206 other_operand = NULL; /* keep compiler quiet */
6209 cost_qual_eval_node(&index_qual_cost, other_operand, root);
6210 qual_arg_cost += index_qual_cost.startup + index_qual_cost.per_tuple;
6212 return qual_arg_cost;
6216 genericcostestimate(PlannerInfo *root,
6220 GenericCosts *costs)
6222 IndexOptInfo *index = path->indexinfo;
6223 List *indexQuals = path->indexquals;
6224 List *indexOrderBys = path->indexorderbys;
6225 Cost indexStartupCost;
6226 Cost indexTotalCost;
6227 Selectivity indexSelectivity;
6228 double indexCorrelation;
6229 double numIndexPages;
6230 double numIndexTuples;
6231 double spc_random_page_cost;
6232 double num_sa_scans;
6233 double num_outer_scans;
6235 double qual_op_cost;
6236 double qual_arg_cost;
6237 List *selectivityQuals;
6241 * If the index is partial, AND the index predicate with the explicitly
6242 * given indexquals to produce a more accurate idea of the index
6245 selectivityQuals = add_predicate_to_quals(index, indexQuals);
6248 * Check for ScalarArrayOpExpr index quals, and estimate the number of
6249 * index scans that will be performed.
6252 foreach(l, indexQuals)
6254 RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
6256 if (IsA(rinfo->clause, ScalarArrayOpExpr))
6258 ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) rinfo->clause;
6259 int alength = estimate_array_length(lsecond(saop->args));
6262 num_sa_scans *= alength;
6266 /* Estimate the fraction of main-table tuples that will be visited */
6267 indexSelectivity = clauselist_selectivity(root, selectivityQuals,
6273 * If caller didn't give us an estimate, estimate the number of index
6274 * tuples that will be visited. We do it in this rather peculiar-looking
6275 * way in order to get the right answer for partial indexes.
6277 numIndexTuples = costs->numIndexTuples;
6278 if (numIndexTuples <= 0.0)
6280 numIndexTuples = indexSelectivity * index->rel->tuples;
6283 * The above calculation counts all the tuples visited across all
6284 * scans induced by ScalarArrayOpExpr nodes. We want to consider the
6285 * average per-indexscan number, so adjust. This is a handy place to
6286 * round to integer, too. (If caller supplied tuple estimate, it's
6287 * responsible for handling these considerations.)
6289 numIndexTuples = rint(numIndexTuples / num_sa_scans);
6293 * We can bound the number of tuples by the index size in any case. Also,
6294 * always estimate at least one tuple is touched, even when
6295 * indexSelectivity estimate is tiny.
6297 if (numIndexTuples > index->tuples)
6298 numIndexTuples = index->tuples;
6299 if (numIndexTuples < 1.0)
6300 numIndexTuples = 1.0;
6303 * Estimate the number of index pages that will be retrieved.
6305 * We use the simplistic method of taking a pro-rata fraction of the total
6306 * number of index pages. In effect, this counts only leaf pages and not
6307 * any overhead such as index metapage or upper tree levels.
6309 * In practice access to upper index levels is often nearly free because
6310 * those tend to stay in cache under load; moreover, the cost involved is
6311 * highly dependent on index type. We therefore ignore such costs here
6312 * and leave it to the caller to add a suitable charge if needed.
6314 if (index->pages > 1 && index->tuples > 1)
6315 numIndexPages = ceil(numIndexTuples * index->pages / index->tuples);
6317 numIndexPages = 1.0;
6319 /* fetch estimated page cost for tablespace containing index */
6320 get_tablespace_page_costs(index->reltablespace,
6321 &spc_random_page_cost,
6325 * Now compute the disk access costs.
6327 * The above calculations are all per-index-scan. However, if we are in a
6328 * nestloop inner scan, we can expect the scan to be repeated (with
6329 * different search keys) for each row of the outer relation. Likewise,
6330 * ScalarArrayOpExpr quals result in multiple index scans. This creates
6331 * the potential for cache effects to reduce the number of disk page
6332 * fetches needed. We want to estimate the average per-scan I/O cost in
6333 * the presence of caching.
6335 * We use the Mackert-Lohman formula (see costsize.c for details) to
6336 * estimate the total number of page fetches that occur. While this
6337 * wasn't what it was designed for, it seems a reasonable model anyway.
6338 * Note that we are counting pages not tuples anymore, so we take N = T =
6339 * index size, as if there were one "tuple" per page.
6341 num_outer_scans = loop_count;
6342 num_scans = num_sa_scans * num_outer_scans;
6346 double pages_fetched;
6348 /* total page fetches ignoring cache effects */
6349 pages_fetched = numIndexPages * num_scans;
6351 /* use Mackert and Lohman formula to adjust for cache effects */
6352 pages_fetched = index_pages_fetched(pages_fetched,
6354 (double) index->pages,
6358 * Now compute the total disk access cost, and then report a pro-rated
6359 * share for each outer scan. (Don't pro-rate for ScalarArrayOpExpr,
6360 * since that's internal to the indexscan.)
6362 indexTotalCost = (pages_fetched * spc_random_page_cost)
6368 * For a single index scan, we just charge spc_random_page_cost per
6371 indexTotalCost = numIndexPages * spc_random_page_cost;
6375 * CPU cost: any complex expressions in the indexquals will need to be
6376 * evaluated once at the start of the scan to reduce them to runtime keys
6377 * to pass to the index AM (see nodeIndexscan.c). We model the per-tuple
6378 * CPU costs as cpu_index_tuple_cost plus one cpu_operator_cost per
6379 * indexqual operator. Because we have numIndexTuples as a per-scan
6380 * number, we have to multiply by num_sa_scans to get the correct result
6381 * for ScalarArrayOpExpr cases. Similarly add in costs for any index
6382 * ORDER BY expressions.
6384 * Note: this neglects the possible costs of rechecking lossy operators.
6385 * Detecting that that might be needed seems more expensive than it's
6386 * worth, though, considering all the other inaccuracies here ...
6388 qual_arg_cost = other_operands_eval_cost(root, qinfos) +
6389 orderby_operands_eval_cost(root, path);
6390 qual_op_cost = cpu_operator_cost *
6391 (list_length(indexQuals) + list_length(indexOrderBys));
6393 indexStartupCost = qual_arg_cost;
6394 indexTotalCost += qual_arg_cost;
6395 indexTotalCost += numIndexTuples * num_sa_scans * (cpu_index_tuple_cost + qual_op_cost);
6398 * Generic assumption about index correlation: there isn't any.
6400 indexCorrelation = 0.0;
6403 * Return everything to caller.
6405 costs->indexStartupCost = indexStartupCost;
6406 costs->indexTotalCost = indexTotalCost;
6407 costs->indexSelectivity = indexSelectivity;
6408 costs->indexCorrelation = indexCorrelation;
6409 costs->numIndexPages = numIndexPages;
6410 costs->numIndexTuples = numIndexTuples;
6411 costs->spc_random_page_cost = spc_random_page_cost;
6412 costs->num_sa_scans = num_sa_scans;
6416 * If the index is partial, add its predicate to the given qual list.
6418 * ANDing the index predicate with the explicitly given indexquals produces
6419 * a more accurate idea of the index's selectivity. However, we need to be
6420 * careful not to insert redundant clauses, because clauselist_selectivity()
6421 * is easily fooled into computing a too-low selectivity estimate. Our
6422 * approach is to add only the predicate clause(s) that cannot be proven to
6423 * be implied by the given indexquals. This successfully handles cases such
6424 * as a qual "x = 42" used with a partial index "WHERE x >= 40 AND x < 50".
6425 * There are many other cases where we won't detect redundancy, leading to a
6426 * too-low selectivity estimate, which will bias the system in favor of using
6427 * partial indexes where possible. That is not necessarily bad though.
6429 * Note that indexQuals contains RestrictInfo nodes while the indpred
6430 * does not, so the output list will be mixed. This is OK for both
6431 * predicate_implied_by() and clauselist_selectivity(), but might be
6432 * problematic if the result were passed to other things.
6435 add_predicate_to_quals(IndexOptInfo *index, List *indexQuals)
6437 List *predExtraQuals = NIL;
6440 if (index->indpred == NIL)
6443 foreach(lc, index->indpred)
6445 Node *predQual = (Node *) lfirst(lc);
6446 List *oneQual = list_make1(predQual);
6448 if (!predicate_implied_by(oneQual, indexQuals))
6449 predExtraQuals = list_concat(predExtraQuals, oneQual);
6451 /* list_concat avoids modifying the passed-in indexQuals list */
6452 return list_concat(predExtraQuals, indexQuals);
6457 btcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
6458 Cost *indexStartupCost, Cost *indexTotalCost,
6459 Selectivity *indexSelectivity, double *indexCorrelation)
6461 IndexOptInfo *index = path->indexinfo;
6466 VariableStatData vardata;
6467 double numIndexTuples;
6469 List *indexBoundQuals;
6473 bool found_is_null_op;
6474 double num_sa_scans;
6477 /* Do preliminary analysis of indexquals */
6478 qinfos = deconstruct_indexquals(path);
6481 * For a btree scan, only leading '=' quals plus inequality quals for the
6482 * immediately next attribute contribute to index selectivity (these are
6483 * the "boundary quals" that determine the starting and stopping points of
6484 * the index scan). Additional quals can suppress visits to the heap, so
6485 * it's OK to count them in indexSelectivity, but they should not count
6486 * for estimating numIndexTuples. So we must examine the given indexquals
6487 * to find out which ones count as boundary quals. We rely on the
6488 * knowledge that they are given in index column order.
6490 * For a RowCompareExpr, we consider only the first column, just as
6491 * rowcomparesel() does.
6493 * If there's a ScalarArrayOpExpr in the quals, we'll actually perform N
6494 * index scans not one, but the ScalarArrayOpExpr's operator can be
6495 * considered to act the same as it normally does.
6497 indexBoundQuals = NIL;
6501 found_is_null_op = false;
6505 IndexQualInfo *qinfo = (IndexQualInfo *) lfirst(lc);
6506 RestrictInfo *rinfo = qinfo->rinfo;
6507 Expr *clause = rinfo->clause;
6511 if (indexcol != qinfo->indexcol)
6513 /* Beginning of a new column's quals */
6515 break; /* done if no '=' qual for indexcol */
6518 if (indexcol != qinfo->indexcol)
6519 break; /* no quals at all for indexcol */
6522 if (IsA(clause, ScalarArrayOpExpr))
6524 int alength = estimate_array_length(qinfo->other_operand);
6527 /* count up number of SA scans induced by indexBoundQuals only */
6529 num_sa_scans *= alength;
6531 else if (IsA(clause, NullTest))
6533 NullTest *nt = (NullTest *) clause;
6535 if (nt->nulltesttype == IS_NULL)
6537 found_is_null_op = true;
6538 /* IS NULL is like = for selectivity determination purposes */
6544 * We would need to commute the clause_op if not varonleft, except
6545 * that we only care if it's equality or not, so that refinement is
6548 clause_op = qinfo->clause_op;
6550 /* check for equality operator */
6551 if (OidIsValid(clause_op))
6553 op_strategy = get_op_opfamily_strategy(clause_op,
6554 index->opfamily[indexcol]);
6555 Assert(op_strategy != 0); /* not a member of opfamily?? */
6556 if (op_strategy == BTEqualStrategyNumber)
6560 indexBoundQuals = lappend(indexBoundQuals, rinfo);
6564 * If index is unique and we found an '=' clause for each column, we can
6565 * just assume numIndexTuples = 1 and skip the expensive
6566 * clauselist_selectivity calculations. However, a ScalarArrayOp or
6567 * NullTest invalidates that theory, even though it sets eqQualHere.
6569 if (index->unique &&
6570 indexcol == index->ncolumns - 1 &&
6574 numIndexTuples = 1.0;
6577 List *selectivityQuals;
6578 Selectivity btreeSelectivity;
6581 * If the index is partial, AND the index predicate with the
6582 * index-bound quals to produce a more accurate idea of the number of
6583 * rows covered by the bound conditions.
6585 selectivityQuals = add_predicate_to_quals(index, indexBoundQuals);
6587 btreeSelectivity = clauselist_selectivity(root, selectivityQuals,
6591 numIndexTuples = btreeSelectivity * index->rel->tuples;
6594 * As in genericcostestimate(), we have to adjust for any
6595 * ScalarArrayOpExpr quals included in indexBoundQuals, and then round
6598 numIndexTuples = rint(numIndexTuples / num_sa_scans);
6602 * Now do generic index cost estimation.
6604 MemSet(&costs, 0, sizeof(costs));
6605 costs.numIndexTuples = numIndexTuples;
6607 genericcostestimate(root, path, loop_count, qinfos, &costs);
6610 * Add a CPU-cost component to represent the costs of initial btree
6611 * descent. We don't charge any I/O cost for touching upper btree levels,
6612 * since they tend to stay in cache, but we still have to do about log2(N)
6613 * comparisons to descend a btree of N leaf tuples. We charge one
6614 * cpu_operator_cost per comparison.
6616 * If there are ScalarArrayOpExprs, charge this once per SA scan. The
6617 * ones after the first one are not startup cost so far as the overall
6618 * plan is concerned, so add them only to "total" cost.
6620 if (index->tuples > 1) /* avoid computing log(0) */
6622 descentCost = ceil(log(index->tuples) / log(2.0)) * cpu_operator_cost;
6623 costs.indexStartupCost += descentCost;
6624 costs.indexTotalCost += costs.num_sa_scans * descentCost;
6628 * Even though we're not charging I/O cost for touching upper btree pages,
6629 * it's still reasonable to charge some CPU cost per page descended
6630 * through. Moreover, if we had no such charge at all, bloated indexes
6631 * would appear to have the same search cost as unbloated ones, at least
6632 * in cases where only a single leaf page is expected to be visited. This
6633 * cost is somewhat arbitrarily set at 50x cpu_operator_cost per page
6634 * touched. The number of such pages is btree tree height plus one (ie,
6635 * we charge for the leaf page too). As above, charge once per SA scan.
6637 descentCost = (index->tree_height + 1) * 50.0 * cpu_operator_cost;
6638 costs.indexStartupCost += descentCost;
6639 costs.indexTotalCost += costs.num_sa_scans * descentCost;
6642 * If we can get an estimate of the first column's ordering correlation C
6643 * from pg_statistic, estimate the index correlation as C for a
6644 * single-column index, or C * 0.75 for multiple columns. (The idea here
6645 * is that multiple columns dilute the importance of the first column's
6646 * ordering, but don't negate it entirely. Before 8.0 we divided the
6647 * correlation by the number of columns, but that seems too strong.)
6649 MemSet(&vardata, 0, sizeof(vardata));
6651 if (index->indexkeys[0] != 0)
6653 /* Simple variable --- look to stats for the underlying table */
6654 RangeTblEntry *rte = planner_rt_fetch(index->rel->relid, root);
6656 Assert(rte->rtekind == RTE_RELATION);
6658 Assert(relid != InvalidOid);
6659 colnum = index->indexkeys[0];
6661 if (get_relation_stats_hook &&
6662 (*get_relation_stats_hook) (root, rte, colnum, &vardata))
6665 * The hook took control of acquiring a stats tuple. If it did
6666 * supply a tuple, it'd better have supplied a freefunc.
6668 if (HeapTupleIsValid(vardata.statsTuple) &&
6670 elog(ERROR, "no function provided to release variable stats with");
6674 vardata.statsTuple = SearchSysCache3(STATRELATTINH,
6675 ObjectIdGetDatum(relid),
6676 Int16GetDatum(colnum),
6677 BoolGetDatum(rte->inh));
6678 vardata.freefunc = ReleaseSysCache;
6683 /* Expression --- maybe there are stats for the index itself */
6684 relid = index->indexoid;
6687 if (get_index_stats_hook &&
6688 (*get_index_stats_hook) (root, relid, colnum, &vardata))
6691 * The hook took control of acquiring a stats tuple. If it did
6692 * supply a tuple, it'd better have supplied a freefunc.
6694 if (HeapTupleIsValid(vardata.statsTuple) &&
6696 elog(ERROR, "no function provided to release variable stats with");
6700 vardata.statsTuple = SearchSysCache3(STATRELATTINH,
6701 ObjectIdGetDatum(relid),
6702 Int16GetDatum(colnum),
6703 BoolGetDatum(false));
6704 vardata.freefunc = ReleaseSysCache;
6708 if (HeapTupleIsValid(vardata.statsTuple))
6714 sortop = get_opfamily_member(index->opfamily[0],
6715 index->opcintype[0],
6716 index->opcintype[0],
6717 BTLessStrategyNumber);
6718 if (OidIsValid(sortop) &&
6719 get_attstatsslot(vardata.statsTuple, InvalidOid, 0,
6720 STATISTIC_KIND_CORRELATION,
6724 &numbers, &nnumbers))
6726 double varCorrelation;
6728 Assert(nnumbers == 1);
6729 varCorrelation = numbers[0];
6731 if (index->reverse_sort[0])
6732 varCorrelation = -varCorrelation;
6734 if (index->ncolumns > 1)
6735 costs.indexCorrelation = varCorrelation * 0.75;
6737 costs.indexCorrelation = varCorrelation;
6739 free_attstatsslot(InvalidOid, NULL, 0, numbers, nnumbers);
6743 ReleaseVariableStats(vardata);
6745 *indexStartupCost = costs.indexStartupCost;
6746 *indexTotalCost = costs.indexTotalCost;
6747 *indexSelectivity = costs.indexSelectivity;
6748 *indexCorrelation = costs.indexCorrelation;
6752 hashcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
6753 Cost *indexStartupCost, Cost *indexTotalCost,
6754 Selectivity *indexSelectivity, double *indexCorrelation)
6759 /* Do preliminary analysis of indexquals */
6760 qinfos = deconstruct_indexquals(path);
6762 MemSet(&costs, 0, sizeof(costs));
6764 genericcostestimate(root, path, loop_count, qinfos, &costs);
6767 * A hash index has no descent costs as such, since the index AM can go
6768 * directly to the target bucket after computing the hash value. There
6769 * are a couple of other hash-specific costs that we could conceivably add
6772 * Ideally we'd charge spc_random_page_cost for each page in the target
6773 * bucket, not just the numIndexPages pages that genericcostestimate
6774 * thought we'd visit. However in most cases we don't know which bucket
6775 * that will be. There's no point in considering the average bucket size
6776 * because the hash AM makes sure that's always one page.
6778 * Likewise, we could consider charging some CPU for each index tuple in
6779 * the bucket, if we knew how many there were. But the per-tuple cost is
6780 * just a hash value comparison, not a general datatype-dependent
6781 * comparison, so any such charge ought to be quite a bit less than
6782 * cpu_operator_cost; which makes it probably not worth worrying about.
6784 * A bigger issue is that chance hash-value collisions will result in
6785 * wasted probes into the heap. We don't currently attempt to model this
6786 * cost on the grounds that it's rare, but maybe it's not rare enough.
6787 * (Any fix for this ought to consider the generic lossy-operator problem,
6788 * though; it's not entirely hash-specific.)
6791 *indexStartupCost = costs.indexStartupCost;
6792 *indexTotalCost = costs.indexTotalCost;
6793 *indexSelectivity = costs.indexSelectivity;
6794 *indexCorrelation = costs.indexCorrelation;
6798 gistcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
6799 Cost *indexStartupCost, Cost *indexTotalCost,
6800 Selectivity *indexSelectivity, double *indexCorrelation)
6802 IndexOptInfo *index = path->indexinfo;
6807 /* Do preliminary analysis of indexquals */
6808 qinfos = deconstruct_indexquals(path);
6810 MemSet(&costs, 0, sizeof(costs));
6812 genericcostestimate(root, path, loop_count, qinfos, &costs);
6815 * We model index descent costs similarly to those for btree, but to do
6816 * that we first need an idea of the tree height. We somewhat arbitrarily
6817 * assume that the fanout is 100, meaning the tree height is at most
6818 * log100(index->pages).
6820 * Although this computation isn't really expensive enough to require
6821 * caching, we might as well use index->tree_height to cache it.
6823 if (index->tree_height < 0) /* unknown? */
6825 if (index->pages > 1) /* avoid computing log(0) */
6826 index->tree_height = (int) (log(index->pages) / log(100.0));
6828 index->tree_height = 0;
6832 * Add a CPU-cost component to represent the costs of initial descent. We
6833 * just use log(N) here not log2(N) since the branching factor isn't
6834 * necessarily two anyway. As for btree, charge once per SA scan.
6836 if (index->tuples > 1) /* avoid computing log(0) */
6838 descentCost = ceil(log(index->tuples)) * cpu_operator_cost;
6839 costs.indexStartupCost += descentCost;
6840 costs.indexTotalCost += costs.num_sa_scans * descentCost;
6844 * Likewise add a per-page charge, calculated the same as for btrees.
6846 descentCost = (index->tree_height + 1) * 50.0 * cpu_operator_cost;
6847 costs.indexStartupCost += descentCost;
6848 costs.indexTotalCost += costs.num_sa_scans * descentCost;
6850 *indexStartupCost = costs.indexStartupCost;
6851 *indexTotalCost = costs.indexTotalCost;
6852 *indexSelectivity = costs.indexSelectivity;
6853 *indexCorrelation = costs.indexCorrelation;
6857 spgcostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
6858 Cost *indexStartupCost, Cost *indexTotalCost,
6859 Selectivity *indexSelectivity, double *indexCorrelation)
6861 IndexOptInfo *index = path->indexinfo;
6866 /* Do preliminary analysis of indexquals */
6867 qinfos = deconstruct_indexquals(path);
6869 MemSet(&costs, 0, sizeof(costs));
6871 genericcostestimate(root, path, loop_count, qinfos, &costs);
6874 * We model index descent costs similarly to those for btree, but to do
6875 * that we first need an idea of the tree height. We somewhat arbitrarily
6876 * assume that the fanout is 100, meaning the tree height is at most
6877 * log100(index->pages).
6879 * Although this computation isn't really expensive enough to require
6880 * caching, we might as well use index->tree_height to cache it.
6882 if (index->tree_height < 0) /* unknown? */
6884 if (index->pages > 1) /* avoid computing log(0) */
6885 index->tree_height = (int) (log(index->pages) / log(100.0));
6887 index->tree_height = 0;
6891 * Add a CPU-cost component to represent the costs of initial descent. We
6892 * just use log(N) here not log2(N) since the branching factor isn't
6893 * necessarily two anyway. As for btree, charge once per SA scan.
6895 if (index->tuples > 1) /* avoid computing log(0) */
6897 descentCost = ceil(log(index->tuples)) * cpu_operator_cost;
6898 costs.indexStartupCost += descentCost;
6899 costs.indexTotalCost += costs.num_sa_scans * descentCost;
6903 * Likewise add a per-page charge, calculated the same as for btrees.
6905 descentCost = (index->tree_height + 1) * 50.0 * cpu_operator_cost;
6906 costs.indexStartupCost += descentCost;
6907 costs.indexTotalCost += costs.num_sa_scans * descentCost;
6909 *indexStartupCost = costs.indexStartupCost;
6910 *indexTotalCost = costs.indexTotalCost;
6911 *indexSelectivity = costs.indexSelectivity;
6912 *indexCorrelation = costs.indexCorrelation;
6917 * Support routines for gincostestimate
6923 double partialEntries;
6924 double exactEntries;
6925 double searchEntries;
6930 * Estimate the number of index terms that need to be searched for while
6931 * testing the given GIN query, and increment the counts in *counts
6932 * appropriately. If the query is unsatisfiable, return false.
6935 gincost_pattern(IndexOptInfo *index, int indexcol,
6936 Oid clause_op, Datum query,
6937 GinQualCounts *counts)
6945 bool *partial_matches = NULL;
6946 Pointer *extra_data = NULL;
6947 bool *nullFlags = NULL;
6948 int32 searchMode = GIN_SEARCH_MODE_DEFAULT;
6952 * Get the operator's strategy number and declared input data types within
6953 * the index opfamily. (We don't need the latter, but we use
6954 * get_op_opfamily_properties because it will throw error if it fails to
6955 * find a matching pg_amop entry.)
6957 get_op_opfamily_properties(clause_op, index->opfamily[indexcol], false,
6958 &strategy_op, &lefttype, &righttype);
6961 * GIN always uses the "default" support functions, which are those with
6962 * lefttype == righttype == the opclass' opcintype (see
6963 * IndexSupportInitialize in relcache.c).
6965 extractProcOid = get_opfamily_proc(index->opfamily[indexcol],
6966 index->opcintype[indexcol],
6967 index->opcintype[indexcol],
6968 GIN_EXTRACTQUERY_PROC);
6970 if (!OidIsValid(extractProcOid))
6972 /* should not happen; throw same error as index_getprocinfo */
6973 elog(ERROR, "missing support function %d for attribute %d of index \"%s\"",
6974 GIN_EXTRACTQUERY_PROC, indexcol + 1,
6975 get_rel_name(index->indexoid));
6979 * Choose collation to pass to extractProc (should match initGinState).
6981 if (OidIsValid(index->indexcollations[indexcol]))
6982 collation = index->indexcollations[indexcol];
6984 collation = DEFAULT_COLLATION_OID;
6986 OidFunctionCall7Coll(extractProcOid,
6989 PointerGetDatum(&nentries),
6990 UInt16GetDatum(strategy_op),
6991 PointerGetDatum(&partial_matches),
6992 PointerGetDatum(&extra_data),
6993 PointerGetDatum(&nullFlags),
6994 PointerGetDatum(&searchMode));
6996 if (nentries <= 0 && searchMode == GIN_SEARCH_MODE_DEFAULT)
6998 /* No match is possible */
7002 for (i = 0; i < nentries; i++)
7005 * For partial match we haven't any information to estimate number of
7006 * matched entries in index, so, we just estimate it as 100
7008 if (partial_matches && partial_matches[i])
7009 counts->partialEntries += 100;
7011 counts->exactEntries++;
7013 counts->searchEntries++;
7016 if (searchMode == GIN_SEARCH_MODE_INCLUDE_EMPTY)
7018 /* Treat "include empty" like an exact-match item */
7019 counts->exactEntries++;
7020 counts->searchEntries++;
7022 else if (searchMode != GIN_SEARCH_MODE_DEFAULT)
7024 /* It's GIN_SEARCH_MODE_ALL */
7025 counts->haveFullScan = true;
7032 * Estimate the number of index terms that need to be searched for while
7033 * testing the given GIN index clause, and increment the counts in *counts
7034 * appropriately. If the query is unsatisfiable, return false.
7037 gincost_opexpr(PlannerInfo *root,
7038 IndexOptInfo *index,
7039 IndexQualInfo *qinfo,
7040 GinQualCounts *counts)
7042 int indexcol = qinfo->indexcol;
7043 Oid clause_op = qinfo->clause_op;
7044 Node *operand = qinfo->other_operand;
7046 if (!qinfo->varonleft)
7048 /* must commute the operator */
7049 clause_op = get_commutator(clause_op);
7052 /* aggressively reduce to a constant, and look through relabeling */
7053 operand = estimate_expression_value(root, operand);
7055 if (IsA(operand, RelabelType))
7056 operand = (Node *) ((RelabelType *) operand)->arg;
7059 * It's impossible to call extractQuery method for unknown operand. So
7060 * unless operand is a Const we can't do much; just assume there will be
7061 * one ordinary search entry from the operand at runtime.
7063 if (!IsA(operand, Const))
7065 counts->exactEntries++;
7066 counts->searchEntries++;
7070 /* If Const is null, there can be no matches */
7071 if (((Const *) operand)->constisnull)
7074 /* Otherwise, apply extractQuery and get the actual term counts */
7075 return gincost_pattern(index, indexcol, clause_op,
7076 ((Const *) operand)->constvalue,
7081 * Estimate the number of index terms that need to be searched for while
7082 * testing the given GIN index clause, and increment the counts in *counts
7083 * appropriately. If the query is unsatisfiable, return false.
7085 * A ScalarArrayOpExpr will give rise to N separate indexscans at runtime,
7086 * each of which involves one value from the RHS array, plus all the
7087 * non-array quals (if any). To model this, we average the counts across
7088 * the RHS elements, and add the averages to the counts in *counts (which
7089 * correspond to per-indexscan costs). We also multiply counts->arrayScans
7090 * by N, causing gincostestimate to scale up its estimates accordingly.
7093 gincost_scalararrayopexpr(PlannerInfo *root,
7094 IndexOptInfo *index,
7095 IndexQualInfo *qinfo,
7096 double numIndexEntries,
7097 GinQualCounts *counts)
7099 int indexcol = qinfo->indexcol;
7100 Oid clause_op = qinfo->clause_op;
7101 Node *rightop = qinfo->other_operand;
7102 ArrayType *arrayval;
7109 GinQualCounts arraycounts;
7110 int numPossible = 0;
7113 Assert(((ScalarArrayOpExpr *) qinfo->rinfo->clause)->useOr);
7115 /* aggressively reduce to a constant, and look through relabeling */
7116 rightop = estimate_expression_value(root, rightop);
7118 if (IsA(rightop, RelabelType))
7119 rightop = (Node *) ((RelabelType *) rightop)->arg;
7122 * It's impossible to call extractQuery method for unknown operand. So
7123 * unless operand is a Const we can't do much; just assume there will be
7124 * one ordinary search entry from each array entry at runtime, and fall
7125 * back on a probably-bad estimate of the number of array entries.
7127 if (!IsA(rightop, Const))
7129 counts->exactEntries++;
7130 counts->searchEntries++;
7131 counts->arrayScans *= estimate_array_length(rightop);
7135 /* If Const is null, there can be no matches */
7136 if (((Const *) rightop)->constisnull)
7139 /* Otherwise, extract the array elements and iterate over them */
7140 arrayval = DatumGetArrayTypeP(((Const *) rightop)->constvalue);
7141 get_typlenbyvalalign(ARR_ELEMTYPE(arrayval),
7142 &elmlen, &elmbyval, &elmalign);
7143 deconstruct_array(arrayval,
7144 ARR_ELEMTYPE(arrayval),
7145 elmlen, elmbyval, elmalign,
7146 &elemValues, &elemNulls, &numElems);
7148 memset(&arraycounts, 0, sizeof(arraycounts));
7150 for (i = 0; i < numElems; i++)
7152 GinQualCounts elemcounts;
7154 /* NULL can't match anything, so ignore, as the executor will */
7158 /* Otherwise, apply extractQuery and get the actual term counts */
7159 memset(&elemcounts, 0, sizeof(elemcounts));
7161 if (gincost_pattern(index, indexcol, clause_op, elemValues[i],
7164 /* We ignore array elements that are unsatisfiable patterns */
7167 if (elemcounts.haveFullScan)
7170 * Full index scan will be required. We treat this as if
7171 * every key in the index had been listed in the query; is
7174 elemcounts.partialEntries = 0;
7175 elemcounts.exactEntries = numIndexEntries;
7176 elemcounts.searchEntries = numIndexEntries;
7178 arraycounts.partialEntries += elemcounts.partialEntries;
7179 arraycounts.exactEntries += elemcounts.exactEntries;
7180 arraycounts.searchEntries += elemcounts.searchEntries;
7184 if (numPossible == 0)
7186 /* No satisfiable patterns in the array */
7191 * Now add the averages to the global counts. This will give us an
7192 * estimate of the average number of terms searched for in each indexscan,
7193 * including contributions from both array and non-array quals.
7195 counts->partialEntries += arraycounts.partialEntries / numPossible;
7196 counts->exactEntries += arraycounts.exactEntries / numPossible;
7197 counts->searchEntries += arraycounts.searchEntries / numPossible;
7199 counts->arrayScans *= numPossible;
7205 * GIN has search behavior completely different from other index types
7208 gincostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
7209 Cost *indexStartupCost, Cost *indexTotalCost,
7210 Selectivity *indexSelectivity, double *indexCorrelation)
7212 IndexOptInfo *index = path->indexinfo;
7213 List *indexQuals = path->indexquals;
7214 List *indexOrderBys = path->indexorderbys;
7217 List *selectivityQuals;
7218 double numPages = index->pages,
7219 numTuples = index->tuples;
7220 double numEntryPages,
7224 GinQualCounts counts;
7226 double partialScale;
7227 double entryPagesFetched,
7229 dataPagesFetchedBySel;
7230 double qual_op_cost,
7232 spc_random_page_cost,
7235 GinStatsData ginStats;
7237 /* Do preliminary analysis of indexquals */
7238 qinfos = deconstruct_indexquals(path);
7241 * Obtain statistical information from the meta page, if possible. Else
7242 * set ginStats to zeroes, and we'll cope below.
7244 if (!index->hypothetical)
7246 indexRel = index_open(index->indexoid, AccessShareLock);
7247 ginGetStats(indexRel, &ginStats);
7248 index_close(indexRel, AccessShareLock);
7252 memset(&ginStats, 0, sizeof(ginStats));
7256 * Assuming we got valid (nonzero) stats at all, nPendingPages can be
7257 * trusted, but the other fields are data as of the last VACUUM. We can
7258 * scale them up to account for growth since then, but that method only
7259 * goes so far; in the worst case, the stats might be for a completely
7260 * empty index, and scaling them will produce pretty bogus numbers.
7261 * Somewhat arbitrarily, set the cutoff for doing scaling at 4X growth; if
7262 * it's grown more than that, fall back to estimating things only from the
7263 * assumed-accurate index size. But we'll trust nPendingPages in any case
7264 * so long as it's not clearly insane, ie, more than the index size.
7266 if (ginStats.nPendingPages < numPages)
7267 numPendingPages = ginStats.nPendingPages;
7269 numPendingPages = 0;
7271 if (numPages > 0 && ginStats.nTotalPages <= numPages &&
7272 ginStats.nTotalPages > numPages / 4 &&
7273 ginStats.nEntryPages > 0 && ginStats.nEntries > 0)
7276 * OK, the stats seem close enough to sane to be trusted. But we
7277 * still need to scale them by the ratio numPages / nTotalPages to
7278 * account for growth since the last VACUUM.
7280 double scale = numPages / ginStats.nTotalPages;
7282 numEntryPages = ceil(ginStats.nEntryPages * scale);
7283 numDataPages = ceil(ginStats.nDataPages * scale);
7284 numEntries = ceil(ginStats.nEntries * scale);
7285 /* ensure we didn't round up too much */
7286 numEntryPages = Min(numEntryPages, numPages - numPendingPages);
7287 numDataPages = Min(numDataPages,
7288 numPages - numPendingPages - numEntryPages);
7293 * We might get here because it's a hypothetical index, or an index
7294 * created pre-9.1 and never vacuumed since upgrading (in which case
7295 * its stats would read as zeroes), or just because it's grown too
7296 * much since the last VACUUM for us to put our faith in scaling.
7298 * Invent some plausible internal statistics based on the index page
7299 * count (and clamp that to at least 10 pages, just in case). We
7300 * estimate that 90% of the index is entry pages, and the rest is data
7301 * pages. Estimate 100 entries per entry page; this is rather bogus
7302 * since it'll depend on the size of the keys, but it's more robust
7303 * than trying to predict the number of entries per heap tuple.
7305 numPages = Max(numPages, 10);
7306 numEntryPages = floor((numPages - numPendingPages) * 0.90);
7307 numDataPages = numPages - numPendingPages - numEntryPages;
7308 numEntries = floor(numEntryPages * 100);
7311 /* In an empty index, numEntries could be zero. Avoid divide-by-zero */
7316 * Include predicate in selectivityQuals (should match
7317 * genericcostestimate)
7319 if (index->indpred != NIL)
7321 List *predExtraQuals = NIL;
7323 foreach(l, index->indpred)
7325 Node *predQual = (Node *) lfirst(l);
7326 List *oneQual = list_make1(predQual);
7328 if (!predicate_implied_by(oneQual, indexQuals))
7329 predExtraQuals = list_concat(predExtraQuals, oneQual);
7331 /* list_concat avoids modifying the passed-in indexQuals list */
7332 selectivityQuals = list_concat(predExtraQuals, indexQuals);
7335 selectivityQuals = indexQuals;
7337 /* Estimate the fraction of main-table tuples that will be visited */
7338 *indexSelectivity = clauselist_selectivity(root, selectivityQuals,
7343 /* fetch estimated page cost for tablespace containing index */
7344 get_tablespace_page_costs(index->reltablespace,
7345 &spc_random_page_cost,
7349 * Generic assumption about index correlation: there isn't any.
7351 *indexCorrelation = 0.0;
7354 * Examine quals to estimate number of search entries & partial matches
7356 memset(&counts, 0, sizeof(counts));
7357 counts.arrayScans = 1;
7358 matchPossible = true;
7362 IndexQualInfo *qinfo = (IndexQualInfo *) lfirst(l);
7363 Expr *clause = qinfo->rinfo->clause;
7365 if (IsA(clause, OpExpr))
7367 matchPossible = gincost_opexpr(root,
7374 else if (IsA(clause, ScalarArrayOpExpr))
7376 matchPossible = gincost_scalararrayopexpr(root,
7386 /* shouldn't be anything else for a GIN index */
7387 elog(ERROR, "unsupported GIN indexqual type: %d",
7388 (int) nodeTag(clause));
7392 /* Fall out if there were any provably-unsatisfiable quals */
7395 *indexStartupCost = 0;
7396 *indexTotalCost = 0;
7397 *indexSelectivity = 0;
7401 if (counts.haveFullScan || indexQuals == NIL)
7404 * Full index scan will be required. We treat this as if every key in
7405 * the index had been listed in the query; is that reasonable?
7407 counts.partialEntries = 0;
7408 counts.exactEntries = numEntries;
7409 counts.searchEntries = numEntries;
7412 /* Will we have more than one iteration of a nestloop scan? */
7413 outer_scans = loop_count;
7416 * Compute cost to begin scan, first of all, pay attention to pending
7419 entryPagesFetched = numPendingPages;
7422 * Estimate number of entry pages read. We need to do
7423 * counts.searchEntries searches. Use a power function as it should be,
7424 * but tuples on leaf pages usually is much greater. Here we include all
7425 * searches in entry tree, including search of first entry in partial
7428 entryPagesFetched += ceil(counts.searchEntries * rint(pow(numEntryPages, 0.15)));
7431 * Add an estimate of entry pages read by partial match algorithm. It's a
7432 * scan over leaf pages in entry tree. We haven't any useful stats here,
7433 * so estimate it as proportion. Because counts.partialEntries is really
7434 * pretty bogus (see code above), it's possible that it is more than
7435 * numEntries; clamp the proportion to ensure sanity.
7437 partialScale = counts.partialEntries / numEntries;
7438 partialScale = Min(partialScale, 1.0);
7440 entryPagesFetched += ceil(numEntryPages * partialScale);
7443 * Partial match algorithm reads all data pages before doing actual scan,
7444 * so it's a startup cost. Again, we haven't any useful stats here, so
7445 * estimate it as proportion.
7447 dataPagesFetched = ceil(numDataPages * partialScale);
7450 * Calculate cache effects if more than one scan due to nestloops or array
7451 * quals. The result is pro-rated per nestloop scan, but the array qual
7452 * factor shouldn't be pro-rated (compare genericcostestimate).
7454 if (outer_scans > 1 || counts.arrayScans > 1)
7456 entryPagesFetched *= outer_scans * counts.arrayScans;
7457 entryPagesFetched = index_pages_fetched(entryPagesFetched,
7458 (BlockNumber) numEntryPages,
7459 numEntryPages, root);
7460 entryPagesFetched /= outer_scans;
7461 dataPagesFetched *= outer_scans * counts.arrayScans;
7462 dataPagesFetched = index_pages_fetched(dataPagesFetched,
7463 (BlockNumber) numDataPages,
7464 numDataPages, root);
7465 dataPagesFetched /= outer_scans;
7469 * Here we use random page cost because logically-close pages could be far
7472 *indexStartupCost = (entryPagesFetched + dataPagesFetched) * spc_random_page_cost;
7475 * Now compute the number of data pages fetched during the scan.
7477 * We assume every entry to have the same number of items, and that there
7478 * is no overlap between them. (XXX: tsvector and array opclasses collect
7479 * statistics on the frequency of individual keys; it would be nice to use
7482 dataPagesFetched = ceil(numDataPages * counts.exactEntries / numEntries);
7485 * If there is a lot of overlap among the entries, in particular if one of
7486 * the entries is very frequent, the above calculation can grossly
7487 * under-estimate. As a simple cross-check, calculate a lower bound based
7488 * on the overall selectivity of the quals. At a minimum, we must read
7489 * one item pointer for each matching entry.
7491 * The width of each item pointer varies, based on the level of
7492 * compression. We don't have statistics on that, but an average of
7493 * around 3 bytes per item is fairly typical.
7495 dataPagesFetchedBySel = ceil(*indexSelectivity *
7496 (numTuples / (BLCKSZ / 3)));
7497 if (dataPagesFetchedBySel > dataPagesFetched)
7498 dataPagesFetched = dataPagesFetchedBySel;
7500 /* Account for cache effects, the same as above */
7501 if (outer_scans > 1 || counts.arrayScans > 1)
7503 dataPagesFetched *= outer_scans * counts.arrayScans;
7504 dataPagesFetched = index_pages_fetched(dataPagesFetched,
7505 (BlockNumber) numDataPages,
7506 numDataPages, root);
7507 dataPagesFetched /= outer_scans;
7510 /* And apply random_page_cost as the cost per page */
7511 *indexTotalCost = *indexStartupCost +
7512 dataPagesFetched * spc_random_page_cost;
7515 * Add on index qual eval costs, much as in genericcostestimate
7517 qual_arg_cost = other_operands_eval_cost(root, qinfos) +
7518 orderby_operands_eval_cost(root, path);
7519 qual_op_cost = cpu_operator_cost *
7520 (list_length(indexQuals) + list_length(indexOrderBys));
7522 *indexStartupCost += qual_arg_cost;
7523 *indexTotalCost += qual_arg_cost;
7524 *indexTotalCost += (numTuples * *indexSelectivity) * (cpu_index_tuple_cost + qual_op_cost);
7528 * BRIN has search behavior completely different from other index types
7531 brincostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
7532 Cost *indexStartupCost, Cost *indexTotalCost,
7533 Selectivity *indexSelectivity, double *indexCorrelation)
7535 IndexOptInfo *index = path->indexinfo;
7536 List *indexQuals = path->indexquals;
7537 List *indexOrderBys = path->indexorderbys;
7538 double numPages = index->pages;
7539 double numTuples = index->tuples;
7541 Cost spc_seq_page_cost;
7542 Cost spc_random_page_cost;
7543 double qual_op_cost;
7544 double qual_arg_cost;
7546 /* Do preliminary analysis of indexquals */
7547 qinfos = deconstruct_indexquals(path);
7549 /* fetch estimated page cost for tablespace containing index */
7550 get_tablespace_page_costs(index->reltablespace,
7551 &spc_random_page_cost,
7552 &spc_seq_page_cost);
7555 * BRIN indexes are always read in full; use that as startup cost.
7557 * XXX maybe only include revmap pages here?
7559 *indexStartupCost = spc_seq_page_cost * numPages * loop_count;
7562 * To read a BRIN index there might be a bit of back and forth over
7563 * regular pages, as revmap might point to them out of sequential order;
7564 * calculate this as reading the whole index in random order.
7566 *indexTotalCost = spc_random_page_cost * numPages * loop_count;
7569 clauselist_selectivity(root, indexQuals,
7570 path->indexinfo->rel->relid,
7572 *indexCorrelation = 1;
7575 * Add on index qual eval costs, much as in genericcostestimate.
7577 qual_arg_cost = other_operands_eval_cost(root, qinfos) +
7578 orderby_operands_eval_cost(root, path);
7579 qual_op_cost = cpu_operator_cost *
7580 (list_length(indexQuals) + list_length(indexOrderBys));
7582 *indexStartupCost += qual_arg_cost;
7583 *indexTotalCost += qual_arg_cost;
7584 *indexTotalCost += (numTuples * *indexSelectivity) * (cpu_index_tuple_cost + qual_op_cost);
7586 /* XXX what about pages_per_range? */