diff options
Diffstat (limited to 'src/backend/utils/adt/selfuncs.c')
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 63 |
1 files changed, 40 insertions, 23 deletions
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index 7c3f77308b5..e4b1acb1f83 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -15,7 +15,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.258 2009/01/01 17:23:50 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.259 2009/02/15 20:16:21 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -234,6 +234,15 @@ var_eq_const(VariableStatData *vardata, Oid operator, if (constisnull) return 0.0; + /* + * If we matched the var to a unique index, assume there is exactly one + * match regardless of anything else. (This is slightly bogus, since + * the index's equality operator might be different from ours, but it's + * more likely to be right than ignoring the information.) + */ + if (vardata->isunique && vardata->rel && vardata->rel->tuples >= 1.0) + return 1.0 / vardata->rel->tuples; + if (HeapTupleIsValid(vardata->statsTuple)) { Form_pg_statistic stats; @@ -357,6 +366,15 @@ var_eq_non_const(VariableStatData *vardata, Oid operator, { double selec; + /* + * If we matched the var to a unique index, assume there is exactly one + * match regardless of anything else. (This is slightly bogus, since + * the index's equality operator might be different from ours, but it's + * more likely to be right than ignoring the information.) + */ + if (vardata->isunique && vardata->rel && vardata->rel->tuples >= 1.0) + return 1.0 / vardata->rel->tuples; + if (HeapTupleIsValid(vardata->statsTuple)) { Form_pg_statistic stats; @@ -3969,6 +3987,8 @@ get_join_variables(PlannerInfo *root, List *args, SpecialJoinInfo *sjinfo, * atttype, atttypmod: type data to pass to get_attstatsslot(). This is * commonly the same as the exposed type of the variable argument, * but can be different in binary-compatible-type cases. + * isunique: TRUE if we were able to match the var to a unique index, + * implying its values are unique for this query. * * Caller is responsible for doing ReleaseVariableStats() before exiting. */ @@ -4005,6 +4025,7 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid, vardata->rel = find_base_rel(root, var->varno); vardata->atttype = var->vartype; vardata->atttypmod = var->vartypmod; + vardata->isunique = has_unique_index(vardata->rel, var->varattno); rte = root->simple_rte_array[var->varno]; @@ -4121,13 +4142,6 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid, if (indexpr_item == NULL) continue; /* no expressions here... */ - /* - * Ignore partial indexes since they probably don't reflect - * whole-relation statistics. Possibly reconsider this later. - */ - if (index->indpred) - continue; - for (pos = 0; pos < index->ncolumns; pos++) { if (index->indexkeys[pos] == 0) @@ -4147,9 +4161,19 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid, */ if (index->unique && index->ncolumns == 1 && - index->indpred == NIL) + (index->indpred == NIL || index->predOK)) vardata->isunique = true; - /* Has it got stats? */ + + /* + * Has it got stats? We only consider stats for + * non-partial indexes, since partial indexes + * probably don't reflect whole-relation statistics; + * the above check for uniqueness is the only info + * we take from a partial index. + * + * An index stats hook, however, must make its own + * decisions about what to do with partial indexes. + */ if (get_index_stats_hook && (*get_index_stats_hook) (root, index->indexoid, pos + 1, vardata)) @@ -4163,7 +4187,7 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid, !vardata->freefunc) elog(ERROR, "no function provided to release variable stats with"); } - else + else if (index->indpred == NIL) { vardata->statsTuple = SearchSysCache(STATRELATT, @@ -4254,19 +4278,12 @@ get_variable_numdistinct(VariableStatData *vardata) /* * If there is a unique index for the variable, assume it is unique no - * matter what pg_statistic says (the statistics could be out of date). - * Can skip search if we already think it's unique. + * matter what pg_statistic says; the statistics could be out of date, + * or we might have found a partial unique index that proves the var + * is unique for this query. */ - if (stadistinct != -1.0) - { - if (vardata->isunique) - stadistinct = -1.0; - else if (vardata->var && IsA(vardata->var, Var) && - vardata->rel && - has_unique_index(vardata->rel, - ((Var *) vardata->var)->varattno)) - stadistinct = -1.0; - } + if (vardata->isunique) + stadistinct = -1.0; /* * If we had an absolute estimate, use that. |