*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.199 2006/04/20 17:50:18 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.200 2006/04/26 18:28:29 momjian Exp $
*
*-------------------------------------------------------------------------
*/
PG_RETURN_VOID();
}
+
+
+#define DEFAULT_PARENT_SEL 0.001
+
+/*
+ * parentsel - Selectivity of parent relationship for ltree data types.
+ */
+Datum
+parentsel(PG_FUNCTION_ARGS)
+{
+ PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+ Oid operator = PG_GETARG_OID(1);
+ List *args = (List *) PG_GETARG_POINTER(2);
+ int varRelid = PG_GETARG_INT32(3);
+ VariableStatData vardata;
+ Node *other;
+ bool varonleft;
+ Datum *values;
+ int nvalues;
+ float4 *numbers;
+ int nnumbers;
+ double selec = 0.0;
+
+ /*
+ * If expression is not variable <@ something or something <@ variable,
+ * then punt and return a default estimate.
+ */
+ if (!get_restriction_variable(root, args, varRelid,
+ &vardata, &other, &varonleft))
+ PG_RETURN_FLOAT8(DEFAULT_PARENT_SEL);
+
+ /*
+ * If the something is a NULL constant, assume operator is strict and
+ * return zero, ie, operator will never return TRUE.
+ */
+ if (IsA(other, Const) &&
+ ((Const *) other)->constisnull)
+ {
+ ReleaseVariableStats(vardata);
+ PG_RETURN_FLOAT8(0.0);
+ }
+
+ if (HeapTupleIsValid(vardata.statsTuple))
+ {
+ Form_pg_statistic stats;
+ double mcvsum = 0.0;
+ double mcvsel = 0.0;
+ double hissel = 0.0;
+
+ stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
+
+ if (IsA(other, Const))
+ {
+ /* Variable is being compared to a known non-null constant */
+ Datum constval = ((Const *) other)->constvalue;
+ bool match = false;
+ int i;
+
+ /*
+ * Is the constant "<@" to any of the column's most common values?
+ */
+ if (get_attstatsslot(vardata.statsTuple,
+ vardata.atttype, vardata.atttypmod,
+ STATISTIC_KIND_MCV, InvalidOid,
+ &values, &nvalues,
+ &numbers, &nnumbers))
+ {
+ FmgrInfo contproc;
+
+ fmgr_info(get_opcode(operator), &contproc);
+
+ for (i = 0; i < nvalues; i++)
+ {
+ /* be careful to apply operator right way 'round */
+ if (varonleft)
+ match = DatumGetBool(FunctionCall2(&contproc,
+ values[i],
+ constval));
+ else
+ match = DatumGetBool(FunctionCall2(&contproc,
+ constval,
+ values[i]));
+
+ /* calculate total selectivity of all most-common-values */
+ mcvsum += numbers[i];
+
+ /* calculate selectivity of matching most-common-values */
+ if (match)
+ mcvsel += numbers[i];
+ }
+ }
+ else
+ {
+ /* no most-common-values info available */
+ values = NULL;
+ numbers = NULL;
+ i = nvalues = nnumbers = 0;
+ }
+
+ free_attstatsslot(vardata.atttype, values, nvalues, NULL, 0);
+
+ /*
+ * Is the constant "<@" to any of the column's histogram values?
+ */
+ if (get_attstatsslot(vardata.statsTuple,
+ vardata.atttype, vardata.atttypmod,
+ STATISTIC_KIND_HISTOGRAM, InvalidOid,
+ &values, &nvalues,
+ NULL, NULL))
+ {
+ FmgrInfo contproc;
+
+ fmgr_info(get_opcode(operator), &contproc);
+
+ for (i = 0; i < nvalues; i++)
+ {
+ /* be careful to apply operator right way 'round */
+ if (varonleft)
+ match = DatumGetBool(FunctionCall2(&contproc,
+ values[i],
+ constval));
+ else
+ match = DatumGetBool(FunctionCall2(&contproc,
+ constval,
+ values[i]));
+ /* count matching histogram values */
+ if (match)
+ hissel++;
+ }
+
+ if (hissel > 0.0)
+ {
+ /*
+ * some matching values found inside histogram, divide
+ * matching entries number by total histogram entries to
+ * get the histogram related selectivity
+ */
+ hissel /= nvalues;
+ }
+ }
+ else
+ {
+ /* no histogram info available */
+ values = NULL;
+ i = nvalues = 0;
+ }
+
+ free_attstatsslot(vardata.atttype, values, nvalues,
+ NULL, 0);
+
+
+ /*
+ * calculate selectivity based on MCV and histogram result
+ * histogram selectivity needs to be scaled down if there are any
+ * most-common-values
+ */
+ selec = mcvsel + hissel * (1.0 - mcvsum);
+
+ /*
+ * don't return 0.0 selectivity unless all table values are inside
+ * mcv
+ */
+ if (selec == 0.0 && mcvsum != 1.0)
+ selec = DEFAULT_PARENT_SEL;
+ }
+ else
+ selec = DEFAULT_PARENT_SEL;
+ }
+ else
+ selec = DEFAULT_PARENT_SEL;
+
+ ReleaseVariableStats(vardata);
+
+ /* result should be in range, but make sure... */
+ CLAMP_PROBABILITY(selec);
+
+ PG_RETURN_FLOAT8((float8) selec);
+}
+
projects / postgresql / commitdiff