1 /*-------------------------------------------------------------------------
4 * Definitions for planner's internal data structures.
7 * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
10 * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.139 2007/02/27 01:11:26 tgl Exp $
12 *-------------------------------------------------------------------------
17 #include "access/sdir.h"
18 #include "nodes/bitmapset.h"
19 #include "nodes/params.h"
20 #include "nodes/parsenodes.h"
21 #include "storage/block.h"
26 * Set of relation identifiers (indexes into the rangetable).
28 typedef Bitmapset *Relids;
31 * When looking for a "cheapest path", this enum specifies whether we want
32 * cheapest startup cost or cheapest total cost.
34 typedef enum CostSelector
36 STARTUP_COST, TOTAL_COST
40 * The cost estimate produced by cost_qual_eval() includes both a one-time
41 * (startup) cost, and a per-tuple cost.
43 typedef struct QualCost
45 Cost startup; /* one-time cost */
46 Cost per_tuple; /* per-evaluation cost */
52 * Global information for planning/optimization
54 * PlannerGlobal holds state for an entire planner invocation; this state
55 * is shared across all levels of sub-Queries that exist in the command being
59 typedef struct PlannerGlobal
63 ParamListInfo boundParams; /* Param values provided to planner() */
65 List *paramlist; /* to keep track of cross-level Params */
67 List *subplans; /* Plans for SubPlan nodes */
69 List *subrtables; /* Rangetables for SubPlan nodes */
71 Bitmapset *rewindPlanIDs; /* indices of subplans that require REWIND */
73 List *finalrtable; /* "flat" rangetable for executor */
76 /* macro for fetching the Plan associated with a SubPlan node */
77 #define planner_subplan_get_plan(root, subplan) \
78 ((Plan *) list_nth((root)->glob->subplans, (subplan)->plan_id - 1))
83 * Per-query information for planning/optimization
85 * This struct is conventionally called "root" in all the planner routines.
86 * It holds links to all of the planner's working state, in addition to the
87 * original Query. Note that at present the planner extensively modifies
88 * the passed-in Query data structure; someday that should stop.
91 typedef struct PlannerInfo
95 Query *parse; /* the Query being planned */
97 PlannerGlobal *glob; /* global info for current planner run */
99 Index query_level; /* 1 at the outermost Query */
102 * simple_rel_array holds pointers to "base rels" and "other rels" (see
103 * comments for RelOptInfo for more info). It is indexed by rangetable
104 * index (so entry 0 is always wasted). Entries can be NULL when an RTE
105 * does not correspond to a base relation, such as a join RTE or an
106 * unreferenced view RTE; or if the RelOptInfo hasn't been made yet.
108 struct RelOptInfo **simple_rel_array; /* All 1-rel RelOptInfos */
109 int simple_rel_array_size; /* allocated size of array */
112 * join_rel_list is a list of all join-relation RelOptInfos we have
113 * considered in this planning run. For small problems we just scan the
114 * list to do lookups, but when there are many join relations we build a
115 * hash table for faster lookups. The hash table is present and valid
116 * when join_rel_hash is not NULL. Note that we still maintain the list
117 * even when using the hash table for lookups; this simplifies life for
120 List *join_rel_list; /* list of join-relation RelOptInfos */
121 struct HTAB *join_rel_hash; /* optional hashtable for join relations */
123 List *resultRelations; /* integer list of RT indexes, or NIL */
125 List *returningLists; /* list of lists of TargetEntry, or NIL */
127 List *init_plans; /* init subplans for query */
129 List *eq_classes; /* list of active EquivalenceClasses */
131 List *canon_pathkeys; /* list of "canonical" PathKeys */
133 List *left_join_clauses; /* list of RestrictInfos for
134 * mergejoinable outer join clauses
135 * w/nonnullable var on left */
137 List *right_join_clauses; /* list of RestrictInfos for
138 * mergejoinable outer join clauses
139 * w/nonnullable var on right */
141 List *full_join_clauses; /* list of RestrictInfos for
142 * mergejoinable full join clauses */
144 List *oj_info_list; /* list of OuterJoinInfos */
146 List *in_info_list; /* list of InClauseInfos */
148 List *append_rel_list; /* list of AppendRelInfos */
150 List *query_pathkeys; /* desired pathkeys for query_planner(), and
151 * actual pathkeys afterwards */
153 List *group_pathkeys; /* groupClause pathkeys, if any */
154 List *sort_pathkeys; /* sortClause pathkeys, if any */
156 MemoryContext planner_cxt; /* context holding PlannerInfo */
158 double total_table_pages; /* # of pages in all tables of query */
160 double tuple_fraction; /* tuple_fraction passed to query_planner */
162 bool hasJoinRTEs; /* true if any RTEs are RTE_JOIN kind */
163 bool hasOuterJoins; /* true if any RTEs are outer joins */
164 bool hasHavingQual; /* true if havingQual was non-null */
165 bool hasPseudoConstantQuals; /* true if any RestrictInfo has
166 * pseudoconstant = true */
172 * Per-relation information for planning/optimization
174 * For planning purposes, a "base rel" is either a plain relation (a table)
175 * or the output of a sub-SELECT or function that appears in the range table.
176 * In either case it is uniquely identified by an RT index. A "joinrel"
177 * is the joining of two or more base rels. A joinrel is identified by
178 * the set of RT indexes for its component baserels. We create RelOptInfo
179 * nodes for each baserel and joinrel, and store them in the PlannerInfo's
180 * simple_rel_array and join_rel_list respectively.
182 * Note that there is only one joinrel for any given set of component
183 * baserels, no matter what order we assemble them in; so an unordered
184 * set is the right datatype to identify it with.
186 * We also have "other rels", which are like base rels in that they refer to
187 * single RT indexes; but they are not part of the join tree, and are given
188 * a different RelOptKind to identify them.
190 * Currently the only kind of otherrels are those made for member relations
191 * of an "append relation", that is an inheritance set or UNION ALL subquery.
192 * An append relation has a parent RTE that is a base rel, which represents
193 * the entire append relation. The member RTEs are otherrels. The parent
194 * is present in the query join tree but the members are not. The member
195 * RTEs and otherrels are used to plan the scans of the individual tables or
196 * subqueries of the append set; then the parent baserel is given an Append
197 * plan comprising the best plans for the individual member rels. (See
198 * comments for AppendRelInfo for more information.)
200 * At one time we also made otherrels to represent join RTEs, for use in
201 * handling join alias Vars. Currently this is not needed because all join
202 * alias Vars are expanded to non-aliased form during preprocess_expression.
204 * Parts of this data structure are specific to various scan and join
205 * mechanisms. It didn't seem worth creating new node types for them.
207 * relids - Set of base-relation identifiers; it is a base relation
208 * if there is just one, a join relation if more than one
209 * rows - estimated number of tuples in the relation after restriction
210 * clauses have been applied (ie, output rows of a plan for it)
211 * width - avg. number of bytes per tuple in the relation after the
212 * appropriate projections have been done (ie, output width)
213 * reltargetlist - List of Var nodes for the attributes we need to
214 * output from this relation (in no particular order)
215 * NOTE: in a child relation, may contain RowExprs
216 * pathlist - List of Path nodes, one for each potentially useful
217 * method of generating the relation
218 * cheapest_startup_path - the pathlist member with lowest startup cost
219 * (regardless of its ordering)
220 * cheapest_total_path - the pathlist member with lowest total cost
221 * (regardless of its ordering)
222 * cheapest_unique_path - for caching cheapest path to produce unique
223 * (no duplicates) output from relation
225 * If the relation is a base relation it will have these fields set:
227 * relid - RTE index (this is redundant with the relids field, but
228 * is provided for convenience of access)
229 * rtekind - distinguishes plain relation, subquery, or function RTE
230 * min_attr, max_attr - range of valid AttrNumbers for rel
231 * attr_needed - array of bitmapsets indicating the highest joinrel
232 * in which each attribute is needed; if bit 0 is set then
233 * the attribute is needed as part of final targetlist
234 * attr_widths - cache space for per-attribute width estimates;
235 * zero means not computed yet
236 * indexlist - list of IndexOptInfo nodes for relation's indexes
237 * (always NIL if it's not a table)
238 * pages - number of disk pages in relation (zero if not a table)
239 * tuples - number of tuples in relation (not considering restrictions)
240 * subplan - plan for subquery (NULL if it's not a subquery)
241 * subrtable - rangetable for subquery (NIL if it's not a subquery)
243 * Note: for a subquery, tuples and subplan are not set immediately
244 * upon creation of the RelOptInfo object; they are filled in when
245 * set_base_rel_pathlist processes the object.
247 * For otherrels that are appendrel members, these fields are filled
248 * in just as for a baserel.
250 * The presence of the remaining fields depends on the restrictions
251 * and joins that the relation participates in:
253 * baserestrictinfo - List of RestrictInfo nodes, containing info about
254 * each non-join qualification clause in which this relation
255 * participates (only used for base rels)
256 * baserestrictcost - Estimated cost of evaluating the baserestrictinfo
257 * clauses at a single tuple (only used for base rels)
258 * joininfo - List of RestrictInfo nodes, containing info about each
259 * join clause in which this relation participates (but
260 * note this excludes clauses that might be derivable from
261 * EquivalenceClasses)
262 * has_eclass_joins - flag that EquivalenceClass joins are possible
263 * index_outer_relids - only used for base rels; set of outer relids
264 * that participate in indexable joinclauses for this rel
265 * index_inner_paths - only used for base rels; list of InnerIndexscanInfo
266 * nodes showing best indexpaths for various subsets of
267 * index_outer_relids.
269 * Note: Keeping a restrictinfo list in the RelOptInfo is useful only for
270 * base rels, because for a join rel the set of clauses that are treated as
271 * restrict clauses varies depending on which sub-relations we choose to join.
272 * (For example, in a 3-base-rel join, a clause relating rels 1 and 2 must be
273 * treated as a restrictclause if we join {1} and {2 3} to make {1 2 3}; but
274 * if we join {1 2} and {3} then that clause will be a restrictclause in {1 2}
275 * and should not be processed again at the level of {1 2 3}.) Therefore,
276 * the restrictinfo list in the join case appears in individual JoinPaths
277 * (field joinrestrictinfo), not in the parent relation. But it's OK for
278 * the RelOptInfo to store the joininfo list, because that is the same
279 * for a given rel no matter how we form it.
281 * We store baserestrictcost in the RelOptInfo (for base relations) because
282 * we know we will need it at least once (to price the sequential scan)
283 * and may need it multiple times to price index scans.
286 typedef enum RelOptKind
290 RELOPT_OTHER_MEMBER_REL
293 typedef struct RelOptInfo
297 RelOptKind reloptkind;
299 /* all relations included in this RelOptInfo */
300 Relids relids; /* set of base relids (rangetable indexes) */
302 /* size estimates generated by planner */
303 double rows; /* estimated number of result tuples */
304 int width; /* estimated avg width of result tuples */
306 /* materialization information */
307 List *reltargetlist; /* needed Vars */
308 List *pathlist; /* Path structures */
309 struct Path *cheapest_startup_path;
310 struct Path *cheapest_total_path;
311 struct Path *cheapest_unique_path;
313 /* information about a base rel (not set for join rels!) */
315 RTEKind rtekind; /* RELATION, SUBQUERY, or FUNCTION */
316 AttrNumber min_attr; /* smallest attrno of rel (often <0) */
317 AttrNumber max_attr; /* largest attrno of rel */
318 Relids *attr_needed; /* array indexed [min_attr .. max_attr] */
319 int32 *attr_widths; /* array indexed [min_attr .. max_attr] */
323 struct Plan *subplan; /* if subquery */
324 List *subrtable; /* if subquery */
326 /* used by various scans and joins: */
327 List *baserestrictinfo; /* RestrictInfo structures (if base
329 QualCost baserestrictcost; /* cost of evaluating the above */
330 List *joininfo; /* RestrictInfo structures for join clauses
331 * involving this rel */
332 bool has_eclass_joins; /* T means joininfo is incomplete */
334 /* cached info about inner indexscan paths for relation: */
335 Relids index_outer_relids; /* other relids in indexable join
337 List *index_inner_paths; /* InnerIndexscanInfo nodes */
340 * Inner indexscans are not in the main pathlist because they are not
341 * usable except in specific join contexts. We use the index_inner_paths
342 * list just to avoid recomputing the best inner indexscan repeatedly for
343 * similar outer relations. See comments for InnerIndexscanInfo.
349 * Per-index information for planning/optimization
351 * Prior to Postgres 7.0, RelOptInfo was used to describe both relations
352 * and indexes, but that created confusion without actually doing anything
353 * useful. So now we have a separate IndexOptInfo struct for indexes.
355 * opfamily[], indexkeys[], fwdsortop[], revsortop[], and nulls_first[]
356 * each have ncolumns entries. Note: for historical reasons, the
357 * opfamily array has an extra entry that is always zero. Some code
358 * scans until it sees a zero entry, rather than looking at ncolumns.
360 * Zeroes in the indexkeys[] array indicate index columns that are
361 * expressions; there is one element in indexprs for each such column.
363 * For an unordered index, the sortop arrays contains zeroes. Note that
364 * fwdsortop[] and nulls_first[] describe the sort ordering of a forward
365 * indexscan; we can also consider a backward indexscan, which will
366 * generate sort order described by revsortop/!nulls_first.
368 * The indexprs and indpred expressions have been run through
369 * prepqual.c and eval_const_expressions() for ease of matching to
370 * WHERE clauses. indpred is in implicit-AND form.
372 typedef struct IndexOptInfo
376 Oid indexoid; /* OID of the index relation */
377 RelOptInfo *rel; /* back-link to index's table */
379 /* statistics from pg_class */
380 BlockNumber pages; /* number of disk pages in index */
381 double tuples; /* number of index tuples in index */
383 /* index descriptor information */
384 int ncolumns; /* number of columns in index */
385 Oid *opfamily; /* OIDs of operator families for columns */
386 int *indexkeys; /* column numbers of index's keys, or 0 */
387 Oid *fwdsortop; /* OIDs of sort operators for each column */
388 Oid *revsortop; /* OIDs of sort operators for backward scan */
389 bool *nulls_first; /* do NULLs come first in the sort order? */
390 Oid relam; /* OID of the access method (in pg_am) */
392 RegProcedure amcostestimate; /* OID of the access method's cost fcn */
394 List *indexprs; /* expressions for non-simple index columns */
395 List *indpred; /* predicate if a partial index, else NIL */
397 bool predOK; /* true if predicate matches query */
398 bool unique; /* true if a unique index */
399 bool amoptionalkey; /* can query omit key for the first column? */
406 * Whenever we can determine that a mergejoinable equality clause A = B is
407 * not delayed by any outer join, we create an EquivalenceClass containing
408 * the expressions A and B to record this knowledge. If we later find another
409 * equivalence B = C, we add C to the existing EquivalenceClass; this may
410 * require merging two existing EquivalenceClasses. At the end of the qual
411 * distribution process, we have sets of values that are known all transitively
412 * equal to each other, where "equal" is according to the rules of the btree
413 * operator family(s) shown in ec_opfamilies. (We restrict an EC to contain
414 * only equalities whose operators belong to the same set of opfamilies. This
415 * could probably be relaxed, but for now it's not worth the trouble, since
416 * nearly all equality operators belong to only one btree opclass anyway.)
418 * We also use EquivalenceClasses as the base structure for PathKeys, letting
419 * us represent knowledge about different sort orderings being equivalent.
420 * Since every PathKey must reference an EquivalenceClass, we will end up
421 * with single-member EquivalenceClasses whenever a sort key expression has
422 * not been equivalenced to anything else. It is also possible that such an
423 * EquivalenceClass will contain a volatile expression ("ORDER BY random()"),
424 * which is a case that can't arise otherwise since clauses containing
425 * volatile functions are never considered mergejoinable. We mark such
426 * EquivalenceClasses specially to prevent them from being merged with
427 * ordinary EquivalenceClasses.
429 * We allow equality clauses appearing below the nullable side of an outer join
430 * to form EquivalenceClasses, but these have a slightly different meaning:
431 * the included values might be all NULL rather than all the same non-null
432 * values. See src/backend/optimizer/README for more on that point.
434 * NB: if ec_merged isn't NULL, this class has been merged into another, and
435 * should be ignored in favor of using the pointed-to class.
437 typedef struct EquivalenceClass
441 List *ec_opfamilies; /* btree operator family OIDs */
442 List *ec_members; /* list of EquivalenceMembers */
443 List *ec_sources; /* list of generating RestrictInfos */
444 List *ec_derives; /* list of derived RestrictInfos */
445 Relids ec_relids; /* all relids appearing in ec_members */
446 bool ec_has_const; /* any pseudoconstants in ec_members? */
447 bool ec_has_volatile; /* the (sole) member is a volatile expr */
448 bool ec_below_outer_join; /* equivalence applies below an OJ */
449 bool ec_broken; /* failed to generate needed clauses? */
450 struct EquivalenceClass *ec_merged; /* set if merged into another EC */
454 * EquivalenceMember - one member expression of an EquivalenceClass
456 * em_is_child signifies that this element was built by transposing a member
457 * for an inheritance parent relation to represent the corresponding expression
458 * on an inheritance child. The element should be ignored for all purposes
459 * except constructing inner-indexscan paths for the child relation. (Other
460 * types of join are driven from transposed joininfo-list entries.) Note
461 * that the EC's ec_relids field does NOT include the child relation.
463 * em_datatype is usually the same as exprType(em_expr), but can be
464 * different when dealing with a binary-compatible opfamily; in particular
465 * anyarray_ops would never work without this. Use em_datatype when
466 * looking up a specific btree operator to work with this expression.
468 typedef struct EquivalenceMember
472 Expr *em_expr; /* the expression represented */
473 Relids em_relids; /* all relids appearing in em_expr */
474 bool em_is_const; /* expression is pseudoconstant? */
475 bool em_is_child; /* derived version for a child relation? */
476 Oid em_datatype; /* the "nominal type" used by the opfamily */
482 * The sort ordering of a path is represented by a list of PathKey nodes.
483 * An empty list implies no known ordering. Otherwise the first item
484 * represents the primary sort key, the second the first secondary sort key,
485 * etc. The value being sorted is represented by linking to an
486 * EquivalenceClass containing that value and including pk_opfamily among its
487 * ec_opfamilies. This is a convenient method because it makes it trivial
488 * to detect equivalent and closely-related orderings. (See optimizer/README
489 * for more information.)
491 * Note: pk_strategy is either BTLessStrategyNumber (for ASC) or
492 * BTGreaterStrategyNumber (for DESC). We assume that all ordering-capable
493 * index types will use btree-compatible strategy numbers.
496 typedef struct PathKey
500 EquivalenceClass *pk_eclass; /* the value that is ordered */
501 Oid pk_opfamily; /* btree opfamily defining the ordering */
502 int pk_strategy; /* sort direction (ASC or DESC) */
503 bool pk_nulls_first; /* do NULLs come before normal values? */
507 * Type "Path" is used as-is for sequential-scan paths. For other
508 * path types it is the first component of a larger struct.
510 * Note: "pathtype" is the NodeTag of the Plan node we could build from this
511 * Path. It is partially redundant with the Path's NodeTag, but allows us
512 * to use the same Path type for multiple Plan types where there is no need
513 * to distinguish the Plan type during path processing.
520 NodeTag pathtype; /* tag identifying scan/join method */
522 RelOptInfo *parent; /* the relation this path can build */
524 /* estimated execution costs for path (see costsize.c for more info) */
525 Cost startup_cost; /* cost expended before fetching any tuples */
526 Cost total_cost; /* total cost (assuming all tuples fetched) */
528 List *pathkeys; /* sort ordering of path's output */
529 /* pathkeys is a List of PathKey nodes; see above */
533 * IndexPath represents an index scan over a single index.
535 * 'indexinfo' is the index to be scanned.
537 * 'indexclauses' is a list of index qualification clauses, with implicit
538 * AND semantics across the list. Each clause is a RestrictInfo node from
539 * the query's WHERE or JOIN conditions.
541 * 'indexquals' has the same structure as 'indexclauses', but it contains
542 * the actual indexqual conditions that can be used with the index.
543 * In simple cases this is identical to 'indexclauses', but when special
544 * indexable operators appear in 'indexclauses', they are replaced by the
545 * derived indexscannable conditions in 'indexquals'.
547 * 'isjoininner' is TRUE if the path is a nestloop inner scan (that is,
548 * some of the index conditions are join rather than restriction clauses).
549 * Note that the path costs will be calculated differently from a plain
550 * indexscan in this case, and in addition there's a special 'rows' value
551 * different from the parent RelOptInfo's (see below).
553 * 'indexscandir' is one of:
554 * ForwardScanDirection: forward scan of an ordered index
555 * BackwardScanDirection: backward scan of an ordered index
556 * NoMovementScanDirection: scan of an unordered index, or don't care
557 * (The executor doesn't care whether it gets ForwardScanDirection or
558 * NoMovementScanDirection for an indexscan, but the planner wants to
559 * distinguish ordered from unordered indexes for building pathkeys.)
561 * 'indextotalcost' and 'indexselectivity' are saved in the IndexPath so that
562 * we need not recompute them when considering using the same index in a
563 * bitmap index/heap scan (see BitmapHeapPath). The costs of the IndexPath
564 * itself represent the costs of an IndexScan plan type.
566 * 'rows' is the estimated result tuple count for the indexscan. This
567 * is the same as path.parent->rows for a simple indexscan, but it is
568 * different for a nestloop inner scan, because the additional indexquals
569 * coming from join clauses make the scan more selective than the parent
570 * rel's restrict clauses alone would do.
573 typedef struct IndexPath
576 IndexOptInfo *indexinfo;
580 ScanDirection indexscandir;
582 Selectivity indexselectivity;
583 double rows; /* estimated number of result tuples */
587 * BitmapHeapPath represents one or more indexscans that generate TID bitmaps
588 * instead of directly accessing the heap, followed by AND/OR combinations
589 * to produce a single bitmap, followed by a heap scan that uses the bitmap.
590 * Note that the output is always considered unordered, since it will come
591 * out in physical heap order no matter what the underlying indexes did.
593 * The individual indexscans are represented by IndexPath nodes, and any
594 * logic on top of them is represented by a tree of BitmapAndPath and
595 * BitmapOrPath nodes. Notice that we can use the same IndexPath node both
596 * to represent a regular IndexScan plan, and as the child of a BitmapHeapPath
597 * that represents scanning the same index using a BitmapIndexScan. The
598 * startup_cost and total_cost figures of an IndexPath always represent the
599 * costs to use it as a regular IndexScan. The costs of a BitmapIndexScan
600 * can be computed using the IndexPath's indextotalcost and indexselectivity.
602 * BitmapHeapPaths can be nestloop inner indexscans. The isjoininner and
603 * rows fields serve the same purpose as for plain IndexPaths.
605 typedef struct BitmapHeapPath
608 Path *bitmapqual; /* IndexPath, BitmapAndPath, BitmapOrPath */
609 bool isjoininner; /* T if it's a nestloop inner scan */
610 double rows; /* estimated number of result tuples */
614 * BitmapAndPath represents a BitmapAnd plan node; it can only appear as
615 * part of the substructure of a BitmapHeapPath. The Path structure is
616 * a bit more heavyweight than we really need for this, but for simplicity
617 * we make it a derivative of Path anyway.
619 typedef struct BitmapAndPath
622 List *bitmapquals; /* IndexPaths and BitmapOrPaths */
623 Selectivity bitmapselectivity;
627 * BitmapOrPath represents a BitmapOr plan node; it can only appear as
628 * part of the substructure of a BitmapHeapPath. The Path structure is
629 * a bit more heavyweight than we really need for this, but for simplicity
630 * we make it a derivative of Path anyway.
632 typedef struct BitmapOrPath
635 List *bitmapquals; /* IndexPaths and BitmapAndPaths */
636 Selectivity bitmapselectivity;
640 * TidPath represents a scan by TID
642 * tidquals is an implicitly OR'ed list of qual expressions of the form
643 * "CTID = pseudoconstant" or "CTID = ANY(pseudoconstant_array)".
644 * Note they are bare expressions, not RestrictInfos.
646 typedef struct TidPath
649 List *tidquals; /* qual(s) involving CTID = something */
653 * AppendPath represents an Append plan, ie, successive execution of
654 * several member plans.
656 * Note: it is possible for "subpaths" to contain only one, or even no,
657 * elements. These cases are optimized during create_append_plan.
659 typedef struct AppendPath
662 List *subpaths; /* list of component Paths */
666 * ResultPath represents use of a Result plan node to compute a variable-free
667 * targetlist with no underlying tables (a "SELECT expressions" query).
668 * The query could have a WHERE clause, too, represented by "quals".
670 * Note that quals is a list of bare clauses, not RestrictInfos.
672 typedef struct ResultPath
679 * MaterialPath represents use of a Material plan node, i.e., caching of
680 * the output of its subpath. This is used when the subpath is expensive
681 * and needs to be scanned repeatedly, or when we need mark/restore ability
682 * and the subpath doesn't have it.
684 typedef struct MaterialPath
691 * UniquePath represents elimination of distinct rows from the output of
694 * This is unlike the other Path nodes in that it can actually generate
695 * different plans: either hash-based or sort-based implementation, or a
696 * no-op if the input path can be proven distinct already. The decision
697 * is sufficiently localized that it's not worth having separate Path node
698 * types. (Note: in the no-op case, we could eliminate the UniquePath node
699 * entirely and just return the subpath; but it's convenient to have a
700 * UniquePath in the path tree to signal upper-level routines that the input
701 * is known distinct.)
705 UNIQUE_PATH_NOOP, /* input is known unique already */
706 UNIQUE_PATH_HASH, /* use hashing */
707 UNIQUE_PATH_SORT /* use sorting */
710 typedef struct UniquePath
714 UniquePathMethod umethod;
715 double rows; /* estimated number of result tuples */
719 * All join-type paths share these fields.
722 typedef struct JoinPath
728 Path *outerjoinpath; /* path for the outer side of the join */
729 Path *innerjoinpath; /* path for the inner side of the join */
731 List *joinrestrictinfo; /* RestrictInfos to apply to join */
734 * See the notes for RelOptInfo to understand why joinrestrictinfo is
735 * needed in JoinPath, and can't be merged into the parent RelOptInfo.
740 * A nested-loop path needs no special fields.
743 typedef JoinPath NestPath;
746 * A mergejoin path has these fields.
748 * path_mergeclauses lists the clauses (in the form of RestrictInfos)
749 * that will be used in the merge.
751 * Note that the mergeclauses are a subset of the parent relation's
752 * restriction-clause list. Any join clauses that are not mergejoinable
753 * appear only in the parent's restrict list, and must be checked by a
754 * qpqual at execution time.
756 * outersortkeys (resp. innersortkeys) is NIL if the outer path
757 * (resp. inner path) is already ordered appropriately for the
758 * mergejoin. If it is not NIL then it is a PathKeys list describing
759 * the ordering that must be created by an explicit sort step.
762 typedef struct MergePath
765 List *path_mergeclauses; /* join clauses to be used for merge */
766 List *outersortkeys; /* keys for explicit sort, if any */
767 List *innersortkeys; /* keys for explicit sort, if any */
771 * A hashjoin path has these fields.
773 * The remarks above for mergeclauses apply for hashclauses as well.
775 * Hashjoin does not care what order its inputs appear in, so we have
776 * no need for sortkeys.
779 typedef struct HashPath
782 List *path_hashclauses; /* join clauses used for hashing */
786 * Restriction clause info.
788 * We create one of these for each AND sub-clause of a restriction condition
789 * (WHERE or JOIN/ON clause). Since the restriction clauses are logically
790 * ANDed, we can use any one of them or any subset of them to filter out
791 * tuples, without having to evaluate the rest. The RestrictInfo node itself
792 * stores data used by the optimizer while choosing the best query plan.
794 * If a restriction clause references a single base relation, it will appear
795 * in the baserestrictinfo list of the RelOptInfo for that base rel.
797 * If a restriction clause references more than one base rel, it will
798 * appear in the joininfo list of every RelOptInfo that describes a strict
799 * subset of the base rels mentioned in the clause. The joininfo lists are
800 * used to drive join tree building by selecting plausible join candidates.
801 * The clause cannot actually be applied until we have built a join rel
802 * containing all the base rels it references, however.
804 * When we construct a join rel that includes all the base rels referenced
805 * in a multi-relation restriction clause, we place that clause into the
806 * joinrestrictinfo lists of paths for the join rel, if neither left nor
807 * right sub-path includes all base rels referenced in the clause. The clause
808 * will be applied at that join level, and will not propagate any further up
809 * the join tree. (Note: the "predicate migration" code was once intended to
810 * push restriction clauses up and down the plan tree based on evaluation
811 * costs, but it's dead code and is unlikely to be resurrected in the
812 * foreseeable future.)
814 * Note that in the presence of more than two rels, a multi-rel restriction
815 * might reach different heights in the join tree depending on the join
816 * sequence we use. So, these clauses cannot be associated directly with
817 * the join RelOptInfo, but must be kept track of on a per-join-path basis.
819 * RestrictInfos that represent equivalence conditions (i.e., mergejoinable
820 * equalities that are not outerjoin-delayed) are handled a bit differently.
821 * Initially we attach them to the EquivalenceClasses that are derived from
822 * them. When we construct a scan or join path, we look through all the
823 * EquivalenceClasses and generate derived RestrictInfos representing the
824 * minimal set of conditions that need to be checked for this particular scan
825 * or join to enforce that all members of each EquivalenceClass are in fact
826 * equal in all rows emitted by the scan or join.
828 * When dealing with outer joins we have to be very careful about pushing qual
829 * clauses up and down the tree. An outer join's own JOIN/ON conditions must
830 * be evaluated exactly at that join node, and any quals appearing in WHERE or
831 * in a JOIN above the outer join cannot be pushed down below the outer join.
832 * Otherwise the outer join will produce wrong results because it will see the
833 * wrong sets of input rows. All quals are stored as RestrictInfo nodes
834 * during planning, but there's a flag to indicate whether a qual has been
835 * pushed down to a lower level than its original syntactic placement in the
836 * join tree would suggest. If an outer join prevents us from pushing a qual
837 * down to its "natural" semantic level (the level associated with just the
838 * base rels used in the qual) then we mark the qual with a "required_relids"
839 * value including more than just the base rels it actually uses. By
840 * pretending that the qual references all the rels appearing in the outer
841 * join, we prevent it from being evaluated below the outer join's joinrel.
842 * When we do form the outer join's joinrel, we still need to distinguish
843 * those quals that are actually in that join's JOIN/ON condition from those
844 * that appeared elsewhere in the tree and were pushed down to the join rel
845 * because they used no other rels. That's what the is_pushed_down flag is
846 * for; it tells us that a qual is not an OUTER JOIN qual for the set of base
847 * rels listed in required_relids. A clause that originally came from WHERE
848 * or an INNER JOIN condition will *always* have its is_pushed_down flag set.
849 * It's possible for an OUTER JOIN clause to be marked is_pushed_down too,
850 * if we decide that it can be pushed down into the nullable side of the join.
851 * In that case it acts as a plain filter qual for wherever it gets evaluated.
853 * When application of a qual must be delayed by outer join, we also mark it
854 * with outerjoin_delayed = true. This isn't redundant with required_relids
855 * because that might equal clause_relids whether or not it's an outer-join
858 * In general, the referenced clause might be arbitrarily complex. The
859 * kinds of clauses we can handle as indexscan quals, mergejoin clauses,
860 * or hashjoin clauses are limited (e.g., no volatile functions). The code
861 * for each kind of path is responsible for identifying the restrict clauses
862 * it can use and ignoring the rest. Clauses not implemented by an indexscan,
863 * mergejoin, or hashjoin will be placed in the plan qual or joinqual field
864 * of the finished Plan node, where they will be enforced by general-purpose
865 * qual-expression-evaluation code. (But we are still entitled to count
866 * their selectivity when estimating the result tuple count, if we
867 * can guess what it is...)
869 * When the referenced clause is an OR clause, we generate a modified copy
870 * in which additional RestrictInfo nodes are inserted below the top-level
871 * OR/AND structure. This is a convenience for OR indexscan processing:
872 * indexquals taken from either the top level or an OR subclause will have
873 * associated RestrictInfo nodes.
875 * The can_join flag is set true if the clause looks potentially useful as
876 * a merge or hash join clause, that is if it is a binary opclause with
877 * nonoverlapping sets of relids referenced in the left and right sides.
878 * (Whether the operator is actually merge or hash joinable isn't checked,
881 * The pseudoconstant flag is set true if the clause contains no Vars of
882 * the current query level and no volatile functions. Such a clause can be
883 * pulled out and used as a one-time qual in a gating Result node. We keep
884 * pseudoconstant clauses in the same lists as other RestrictInfos so that
885 * the regular clause-pushing machinery can assign them to the correct join
886 * level, but they need to be treated specially for cost and selectivity
887 * estimates. Note that a pseudoconstant clause can never be an indexqual
888 * or merge or hash join clause, so it's of no interest to large parts of
891 * When join clauses are generated from EquivalenceClasses, there may be
892 * several equally valid ways to enforce join equivalence, of which we need
893 * apply only one. We mark clauses of this kind by setting parent_ec to
894 * point to the generating EquivalenceClass. Multiple clauses with the same
895 * parent_ec in the same join are redundant.
898 typedef struct RestrictInfo
902 Expr *clause; /* the represented clause of WHERE or JOIN */
904 bool is_pushed_down; /* TRUE if clause was pushed down in level */
906 bool outerjoin_delayed; /* TRUE if delayed by outer join */
908 bool can_join; /* see comment above */
910 bool pseudoconstant; /* see comment above */
912 /* The set of relids (varnos) actually referenced in the clause: */
913 Relids clause_relids;
915 /* The set of relids required to evaluate the clause: */
916 Relids required_relids;
918 /* These fields are set for any binary opclause: */
919 Relids left_relids; /* relids in left side of clause */
920 Relids right_relids; /* relids in right side of clause */
922 /* This field is NULL unless clause is an OR clause: */
923 Expr *orclause; /* modified clause with RestrictInfos */
925 /* This field is NULL unless clause is potentially redundant: */
926 EquivalenceClass *parent_ec; /* generating EquivalenceClass */
928 /* cache space for cost and selectivity */
929 QualCost eval_cost; /* eval cost of clause; -1 if not yet set */
930 Selectivity this_selec; /* selectivity; -1 if not yet set */
932 /* valid if clause is mergejoinable, else NIL */
933 List *mergeopfamilies; /* opfamilies containing clause operator */
935 /* cache space for mergeclause processing; NULL if not yet set */
936 EquivalenceClass *left_ec; /* EquivalenceClass containing lefthand */
937 EquivalenceClass *right_ec; /* EquivalenceClass containing righthand */
938 EquivalenceMember *left_em; /* EquivalenceMember for lefthand */
939 EquivalenceMember *right_em; /* EquivalenceMember for righthand */
940 List *scansel_cache; /* list of MergeScanSelCache structs */
942 /* transient workspace for use while considering a specific join path */
943 bool outer_is_left; /* T = outer var on left, F = on right */
945 /* valid if clause is hashjoinable, else InvalidOid: */
946 Oid hashjoinoperator; /* copy of clause operator */
948 /* cache space for hashclause processing; -1 if not yet set */
949 Selectivity left_bucketsize; /* avg bucketsize of left side */
950 Selectivity right_bucketsize; /* avg bucketsize of right side */
954 * Since mergejoinscansel() is a relatively expensive function, and would
955 * otherwise be invoked many times while planning a large join tree,
956 * we go out of our way to cache its results. Each mergejoinable
957 * RestrictInfo carries a list of the specific sort orderings that have
958 * been considered for use with it, and the resulting selectivities.
960 typedef struct MergeScanSelCache
962 /* Ordering details (cache lookup key) */
963 Oid opfamily; /* btree opfamily defining the ordering */
964 int strategy; /* sort direction (ASC or DESC) */
965 bool nulls_first; /* do NULLs come before normal values? */
967 Selectivity leftscansel; /* scan fraction for clause left side */
968 Selectivity rightscansel; /* scan fraction for clause right side */
972 * Inner indexscan info.
974 * An inner indexscan is one that uses one or more joinclauses as index
975 * conditions (perhaps in addition to plain restriction clauses). So it
976 * can only be used as the inner path of a nestloop join where the outer
977 * relation includes all other relids appearing in those joinclauses.
978 * The set of usable joinclauses, and thus the best inner indexscan,
979 * thus varies depending on which outer relation we consider; so we have
980 * to recompute the best such path for every join. To avoid lots of
981 * redundant computation, we cache the results of such searches. For
982 * each relation we compute the set of possible otherrelids (all relids
983 * appearing in joinquals that could become indexquals for this table).
984 * Two outer relations whose relids have the same intersection with this
985 * set will have the same set of available joinclauses and thus the same
986 * best inner indexscan for the inner relation. By taking the intersection
987 * before scanning the cache, we avoid recomputing when considering
988 * join rels that differ only by the inclusion of irrelevant other rels.
990 * The search key also includes a bool showing whether the join being
991 * considered is an outer join. Since we constrain the join order for
992 * outer joins, I believe that this bool can only have one possible value
993 * for any particular base relation; but store it anyway to avoid confusion.
996 typedef struct InnerIndexscanInfo
999 /* The lookup key: */
1000 Relids other_relids; /* a set of relevant other relids */
1001 bool isouterjoin; /* true if join is outer */
1002 /* Best path for this lookup key: */
1003 Path *best_innerpath; /* best inner indexscan, or NULL if none */
1004 } InnerIndexscanInfo;
1009 * One-sided outer joins constrain the order of joining partially but not
1010 * completely. We flatten such joins into the planner's top-level list of
1011 * relations to join, but record information about each outer join in an
1012 * OuterJoinInfo struct. These structs are kept in the PlannerInfo node's
1015 * min_lefthand and min_righthand are the sets of base relids that must be
1016 * available on each side when performing the outer join. lhs_strict is
1017 * true if the outer join's condition cannot succeed when the LHS variables
1018 * are all NULL (this means that the outer join can commute with upper-level
1019 * outer joins even if it appears in their RHS). We don't bother to set
1020 * lhs_strict for FULL JOINs, however.
1022 * It is not valid for either min_lefthand or min_righthand to be empty sets;
1023 * if they were, this would break the logic that enforces join order.
1025 * Note: OuterJoinInfo directly represents only LEFT JOIN and FULL JOIN;
1026 * RIGHT JOIN is handled by switching the inputs to make it a LEFT JOIN.
1027 * We make an OuterJoinInfo for FULL JOINs even though there is no flexibility
1028 * of planning for them, because this simplifies make_join_rel()'s API.
1031 typedef struct OuterJoinInfo
1034 Relids min_lefthand; /* base relids in minimum LHS for join */
1035 Relids min_righthand; /* base relids in minimum RHS for join */
1036 bool is_full_join; /* it's a FULL OUTER JOIN */
1037 bool lhs_strict; /* joinclause is strict for some LHS rel */
1043 * When we convert top-level IN quals into join operations, we must restrict
1044 * the order of joining and use special join methods at some join points.
1045 * We record information about each such IN clause in an InClauseInfo struct.
1046 * These structs are kept in the PlannerInfo node's in_info_list.
1048 * Note: sub_targetlist is just a list of Vars or expressions; it does not
1049 * contain TargetEntry nodes.
1052 typedef struct InClauseInfo
1055 Relids lefthand; /* base relids in lefthand expressions */
1056 Relids righthand; /* base relids coming from the subselect */
1057 List *sub_targetlist; /* targetlist of original RHS subquery */
1058 List *in_operators; /* OIDs of the IN's equality operator(s) */
1062 * Append-relation info.
1064 * When we expand an inheritable table or a UNION-ALL subselect into an
1065 * "append relation" (essentially, a list of child RTEs), we build an
1066 * AppendRelInfo for each child RTE. The list of AppendRelInfos indicates
1067 * which child RTEs must be included when expanding the parent, and each
1068 * node carries information needed to translate Vars referencing the parent
1069 * into Vars referencing that child.
1071 * These structs are kept in the PlannerInfo node's append_rel_list.
1072 * Note that we just throw all the structs into one list, and scan the
1073 * whole list when desiring to expand any one parent. We could have used
1074 * a more complex data structure (eg, one list per parent), but this would
1075 * be harder to update during operations such as pulling up subqueries,
1076 * and not really any easier to scan. Considering that typical queries
1077 * will not have many different append parents, it doesn't seem worthwhile
1078 * to complicate things.
1080 * Note: after completion of the planner prep phase, any given RTE is an
1081 * append parent having entries in append_rel_list if and only if its
1082 * "inh" flag is set. We clear "inh" for plain tables that turn out not
1083 * to have inheritance children, and (in an abuse of the original meaning
1084 * of the flag) we set "inh" for subquery RTEs that turn out to be
1085 * flattenable UNION ALL queries. This lets us avoid useless searches
1086 * of append_rel_list.
1088 * Note: the data structure assumes that append-rel members are single
1089 * baserels. This is OK for inheritance, but it prevents us from pulling
1090 * up a UNION ALL member subquery if it contains a join. While that could
1091 * be fixed with a more complex data structure, at present there's not much
1092 * point because no improvement in the plan could result.
1095 typedef struct AppendRelInfo
1100 * These fields uniquely identify this append relationship. There can be
1101 * (in fact, always should be) multiple AppendRelInfos for the same
1102 * parent_relid, but never more than one per child_relid, since a given
1103 * RTE cannot be a child of more than one append parent.
1105 Index parent_relid; /* RT index of append parent rel */
1106 Index child_relid; /* RT index of append child rel */
1109 * For an inheritance appendrel, the parent and child are both regular
1110 * relations, and we store their rowtype OIDs here for use in translating
1111 * whole-row Vars. For a UNION-ALL appendrel, the parent and child are
1112 * both subqueries with no named rowtype, and we store InvalidOid here.
1114 Oid parent_reltype; /* OID of parent's composite type */
1115 Oid child_reltype; /* OID of child's composite type */
1118 * The N'th element of this list is the integer column number of the child
1119 * column corresponding to the N'th column of the parent. A list element
1120 * is zero if it corresponds to a dropped column of the parent (this is
1121 * only possible for inheritance cases, not UNION ALL).
1123 List *col_mappings; /* list of child attribute numbers */
1126 * The N'th element of this list is a Var or expression representing the
1127 * child column corresponding to the N'th column of the parent. This is
1128 * used to translate Vars referencing the parent rel into references to
1129 * the child. A list element is NULL if it corresponds to a dropped
1130 * column of the parent (this is only possible for inheritance cases, not
1133 * This might seem redundant with the col_mappings data, but it is handy
1134 * because flattening of sub-SELECTs that are members of a UNION ALL will
1135 * cause changes in the expressions that need to be substituted for a
1136 * parent Var. Adjusting this data structure lets us track what really
1137 * needs to be substituted.
1139 * Notice we only store entries for user columns (attno > 0). Whole-row
1140 * Vars are special-cased, and system columns (attno < 0) need no special
1141 * translation since their attnos are the same for all tables.
1143 * Caution: the Vars have varlevelsup = 0. Be careful to adjust as needed
1144 * when copying into a subquery.
1146 List *translated_vars; /* Expressions in the child's Vars */
1149 * We store the parent table's OID here for inheritance, or InvalidOid for
1150 * UNION ALL. This is only needed to help in generating error messages if
1151 * an attempt is made to reference a dropped parent column.
1153 Oid parent_reloid; /* OID of parent relation */
1157 * glob->paramlist keeps track of the PARAM_EXEC slots that we have decided
1158 * we need for the query. At runtime these slots are used to pass values
1159 * either down into subqueries (for outer references in subqueries) or up out
1160 * of subqueries (for the results of a subplan). The n'th entry in the list
1161 * (n counts from 0) corresponds to Param->paramid = n.
1163 * Each paramlist item shows the absolute query level it is associated with,
1164 * where the outermost query is level 1 and nested subqueries have higher
1165 * numbers. The item the parameter slot represents can be one of three kinds:
1167 * A Var: the slot represents a variable of that level that must be passed
1168 * down because subqueries have outer references to it. The varlevelsup
1169 * value in the Var will always be zero.
1171 * An Aggref (with an expression tree representing its argument): the slot
1172 * represents an aggregate expression that is an outer reference for some
1173 * subquery. The Aggref itself has agglevelsup = 0, and its argument tree
1174 * is adjusted to match in level.
1176 * A Param: the slot holds the result of a subplan (it is a setParam item
1177 * for that subplan). The absolute level shown for such items corresponds
1178 * to the parent query of the subplan.
1180 * Note: we detect duplicate Var parameters and coalesce them into one slot,
1181 * but we do not do this for Aggref or Param slots.
1183 typedef struct PlannerParamItem
1187 Node *item; /* the Var, Aggref, or Param */
1188 Index abslevel; /* its absolute query level */
1191 #endif /* RELATION_H */