diff options
Diffstat (limited to 'src/backend/optimizer/plan/initsplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/initsplan.c | 181 |
1 files changed, 180 insertions, 1 deletions
diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c index 49d776d9295..a7655e4a710 100644 --- a/src/backend/optimizer/plan/initsplan.c +++ b/src/backend/optimizer/plan/initsplan.c @@ -17,6 +17,7 @@ #include "catalog/pg_type.h" #include "nodes/nodeFuncs.h" #include "optimizer/clauses.h" +#include "optimizer/cost.h" #include "optimizer/joininfo.h" #include "optimizer/pathnode.h" #include "optimizer/paths.h" @@ -55,6 +56,7 @@ static SpecialJoinInfo *make_outerjoininfo(PlannerInfo *root, Relids left_rels, Relids right_rels, Relids inner_join_rels, JoinType jointype, List *clause); +static void compute_semijoin_info(SpecialJoinInfo *sjinfo, List *clause); static void distribute_qual_to_rels(PlannerInfo *root, Node *clause, bool is_deduced, bool below_outer_join, @@ -1085,7 +1087,8 @@ make_outerjoininfo(PlannerInfo *root, sjinfo->jointype = jointype; /* this always starts out false */ sjinfo->delay_upper_joins = false; - sjinfo->join_quals = clause; + + compute_semijoin_info(sjinfo, clause); /* If it's a full join, no need to be very smart */ if (jointype == JOIN_FULL) @@ -1237,6 +1240,182 @@ make_outerjoininfo(PlannerInfo *root, return sjinfo; } +/* + * compute_semijoin_info + * Fill semijoin-related fields of a new SpecialJoinInfo + * + * Note: this relies on only the jointype and syn_righthand fields of the + * SpecialJoinInfo; the rest may not be set yet. + */ +static void +compute_semijoin_info(SpecialJoinInfo *sjinfo, List *clause) +{ + List *semi_operators; + List *semi_rhs_exprs; + bool all_btree; + bool all_hash; + ListCell *lc; + + /* Initialize semijoin-related fields in case we can't unique-ify */ + sjinfo->semi_can_btree = false; + sjinfo->semi_can_hash = false; + sjinfo->semi_operators = NIL; + sjinfo->semi_rhs_exprs = NIL; + + /* Nothing more to do if it's not a semijoin */ + if (sjinfo->jointype != JOIN_SEMI) + return; + + /* + * Look to see whether the semijoin's join quals consist of AND'ed + * equality operators, with (only) RHS variables on only one side of each + * one. If so, we can figure out how to enforce uniqueness for the RHS. + * + * Note that the input clause list is the list of quals that are + * *syntactically* associated with the semijoin, which in practice means + * the synthesized comparison list for an IN or the WHERE of an EXISTS. + * Particularly in the latter case, it might contain clauses that aren't + * *semantically* associated with the join, but refer to just one side or + * the other. We can ignore such clauses here, as they will just drop + * down to be processed within one side or the other. (It is okay to + * consider only the syntactically-associated clauses here because for a + * semijoin, no higher-level quals could refer to the RHS, and so there + * can be no other quals that are semantically associated with this join. + * We do things this way because it is useful to have the set of potential + * unique-ification expressions before we can extract the list of quals + * that are actually semantically associated with the particular join.) + * + * Note that the semi_operators list consists of the joinqual operators + * themselves (but commuted if needed to put the RHS value on the right). + * These could be cross-type operators, in which case the operator + * actually needed for uniqueness is a related single-type operator. We + * assume here that that operator will be available from the btree or hash + * opclass when the time comes ... if not, create_unique_plan() will fail. + */ + semi_operators = NIL; + semi_rhs_exprs = NIL; + all_btree = true; + all_hash = enable_hashagg; /* don't consider hash if not enabled */ + foreach(lc, clause) + { + OpExpr *op = (OpExpr *) lfirst(lc); + Oid opno; + Node *left_expr; + Node *right_expr; + Relids left_varnos; + Relids right_varnos; + Relids all_varnos; + Oid opinputtype; + + /* Is it a binary opclause? */ + if (!IsA(op, OpExpr) || + list_length(op->args) != 2) + { + /* No, but does it reference both sides? */ + all_varnos = pull_varnos((Node *) op); + if (!bms_overlap(all_varnos, sjinfo->syn_righthand) || + bms_is_subset(all_varnos, sjinfo->syn_righthand)) + { + /* + * Clause refers to only one rel, so ignore it --- unless it + * contains volatile functions, in which case we'd better + * punt. + */ + if (contain_volatile_functions((Node *) op)) + return; + continue; + } + /* Non-operator clause referencing both sides, must punt */ + return; + } + + /* Extract data from binary opclause */ + opno = op->opno; + left_expr = linitial(op->args); + right_expr = lsecond(op->args); + left_varnos = pull_varnos(left_expr); + right_varnos = pull_varnos(right_expr); + all_varnos = bms_union(left_varnos, right_varnos); + opinputtype = exprType(left_expr); + + /* Does it reference both sides? */ + if (!bms_overlap(all_varnos, sjinfo->syn_righthand) || + bms_is_subset(all_varnos, sjinfo->syn_righthand)) + { + /* + * Clause refers to only one rel, so ignore it --- unless it + * contains volatile functions, in which case we'd better punt. + */ + if (contain_volatile_functions((Node *) op)) + return; + continue; + } + + /* check rel membership of arguments */ + if (!bms_is_empty(right_varnos) && + bms_is_subset(right_varnos, sjinfo->syn_righthand) && + !bms_overlap(left_varnos, sjinfo->syn_righthand)) + { + /* typical case, right_expr is RHS variable */ + } + else if (!bms_is_empty(left_varnos) && + bms_is_subset(left_varnos, sjinfo->syn_righthand) && + !bms_overlap(right_varnos, sjinfo->syn_righthand)) + { + /* flipped case, left_expr is RHS variable */ + opno = get_commutator(opno); + if (!OidIsValid(opno)) + return; + right_expr = left_expr; + } + else + { + /* mixed membership of args, punt */ + return; + } + + /* all operators must be btree equality or hash equality */ + if (all_btree) + { + /* oprcanmerge is considered a hint... */ + if (!op_mergejoinable(opno, opinputtype) || + get_mergejoin_opfamilies(opno) == NIL) + all_btree = false; + } + if (all_hash) + { + /* ... but oprcanhash had better be correct */ + if (!op_hashjoinable(opno, opinputtype)) + all_hash = false; + } + if (!(all_btree || all_hash)) + return; + + /* so far so good, keep building lists */ + semi_operators = lappend_oid(semi_operators, opno); + semi_rhs_exprs = lappend(semi_rhs_exprs, copyObject(right_expr)); + } + + /* Punt if we didn't find at least one column to unique-ify */ + if (semi_rhs_exprs == NIL) + return; + + /* + * The expressions we'd need to unique-ify mustn't be volatile. + */ + if (contain_volatile_functions((Node *) semi_rhs_exprs)) + return; + + /* + * If we get here, we can unique-ify the semijoin's RHS using at least one + * of sorting and hashing. Save the information about how to do that. + */ + sjinfo->semi_can_btree = all_btree; + sjinfo->semi_can_hash = all_hash; + sjinfo->semi_operators = semi_operators; + sjinfo->semi_rhs_exprs = semi_rhs_exprs; +} + /***************************************************************************** * |