diff options
Diffstat (limited to 'src/backend/optimizer/plan/initsplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/initsplan.c | 165 |
1 files changed, 87 insertions, 78 deletions
diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c index afcb4528326..61edf1c22d4 100644 --- a/src/backend/optimizer/plan/initsplan.c +++ b/src/backend/optimizer/plan/initsplan.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/initsplan.c,v 1.88 2003/07/28 00:09:15 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/initsplan.c,v 1.89 2003/08/04 00:43:20 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -36,12 +36,12 @@ static void mark_baserels_for_outer_join(Query *root, Relids rels, Relids outerrels); static void distribute_qual_to_rels(Query *root, Node *clause, - bool ispusheddown, - bool isdeduced, - Relids outerjoin_nonnullable, - Relids qualscope); + bool ispusheddown, + bool isdeduced, + Relids outerjoin_nonnullable, + Relids qualscope); static void add_vars_to_targetlist(Query *root, List *vars, - Relids where_needed); + Relids where_needed); static bool qual_is_redundant(Query *root, RestrictInfo *restrictinfo, List *restrictlist); static void check_mergejoinable(RestrictInfo *restrictinfo); @@ -83,9 +83,7 @@ add_base_rels_to_query(Query *root, Node *jtnode) List *l; foreach(l, f->fromlist) - { add_base_rels_to_query(root, lfirst(l)); - } } else if (IsA(jtnode, JoinExpr)) { @@ -93,13 +91,14 @@ add_base_rels_to_query(Query *root, Node *jtnode) add_base_rels_to_query(root, j->larg); add_base_rels_to_query(root, j->rarg); + /* * Safety check: join RTEs should not be SELECT FOR UPDATE targets */ if (intMember(j->rtindex, root->rowMarks)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), - errmsg("SELECT FOR UPDATE cannot be applied to a join"))); + errmsg("SELECT FOR UPDATE cannot be applied to a join"))); } else elog(ERROR, "unrecognized node type: %d", @@ -247,14 +246,14 @@ distribute_quals_to_rels(Query *root, Node *jtnode) * Order of operations here is subtle and critical. First we * recurse to handle sub-JOINs. Their join quals will be placed * without regard for whether this level is an outer join, which - * is correct. Then we place our own join quals, which are restricted - * by lower outer joins in any case, and are forced to this level if - * this is an outer join and they mention the outer side. Finally, if - * this is an outer join, we mark baserels contained within the inner - * side(s) with our own rel set; this will prevent quals above us in - * the join tree that use those rels from being pushed down below this - * level. (It's okay for upper quals to be pushed down to the outer - * side, however.) + * is correct. Then we place our own join quals, which are + * restricted by lower outer joins in any case, and are forced to + * this level if this is an outer join and they mention the outer + * side. Finally, if this is an outer join, we mark baserels + * contained within the inner side(s) with our own rel set; this + * will prevent quals above us in the join tree that use those + * rels from being pushed down below this level. (It's okay for + * upper quals to be pushed down to the outer side, however.) */ leftids = distribute_quals_to_rels(root, j->larg); rightids = distribute_quals_to_rels(root, j->rarg); @@ -390,9 +389,10 @@ distribute_qual_to_rels(Query *root, Node *clause, restrictinfo->clause = (Expr *) clause; restrictinfo->subclauseindices = NIL; - restrictinfo->eval_cost.startup = -1; /* not computed until needed */ + restrictinfo->eval_cost.startup = -1; /* not computed until + * needed */ restrictinfo->this_selec = -1; /* not computed until needed */ - restrictinfo->left_relids = NULL; /* set below, if join clause */ + restrictinfo->left_relids = NULL; /* set below, if join clause */ restrictinfo->right_relids = NULL; restrictinfo->mergejoinoperator = InvalidOid; restrictinfo->left_sortop = InvalidOid; @@ -435,10 +435,10 @@ distribute_qual_to_rels(Query *root, Node *clause, if (isdeduced) { /* - * If the qual came from implied-equality deduction, we can evaluate - * the qual at its natural semantic level. It is not affected by - * any outer-join rules (else we'd not have decided the vars were - * equal). + * If the qual came from implied-equality deduction, we can + * evaluate the qual at its natural semantic level. It is not + * affected by any outer-join rules (else we'd not have decided + * the vars were equal). */ Assert(bms_equal(relids, qualscope)); can_be_equijoin = true; @@ -446,12 +446,13 @@ distribute_qual_to_rels(Query *root, Node *clause, else if (bms_overlap(relids, outerjoin_nonnullable)) { /* - * The qual is attached to an outer join and mentions (some of the) - * rels on the nonnullable side. Force the qual to be evaluated - * exactly at the level of joining corresponding to the outer join. - * We cannot let it get pushed down into the nonnullable side, since - * then we'd produce no output rows, rather than the intended single - * null-extended row, for any nonnullable-side rows failing the qual. + * The qual is attached to an outer join and mentions (some of + * the) rels on the nonnullable side. Force the qual to be + * evaluated exactly at the level of joining corresponding to the + * outer join. We cannot let it get pushed down into the + * nonnullable side, since then we'd produce no output rows, + * rather than the intended single null-extended row, for any + * nonnullable-side rows failing the qual. * * Note: an outer-join qual that mentions only nullable-side rels can * be pushed down into the nullable side without changing the join @@ -464,13 +465,14 @@ distribute_qual_to_rels(Query *root, Node *clause, { /* * For a non-outer-join qual, we can evaluate the qual as soon as - * (1) we have all the rels it mentions, and (2) we are at or above - * any outer joins that can null any of these rels and are below the - * syntactic location of the given qual. To enforce the latter, scan - * the base rels listed in relids, and merge their outer-join sets - * into the clause's own reference list. At the time we are called, - * the outerjoinset of each baserel will show exactly those outer - * joins that are below the qual in the join tree. + * (1) we have all the rels it mentions, and (2) we are at or + * above any outer joins that can null any of these rels and are + * below the syntactic location of the given qual. To enforce the + * latter, scan the base rels listed in relids, and merge their + * outer-join sets into the clause's own reference list. At the + * time we are called, the outerjoinset of each baserel will show + * exactly those outer joins that are below the qual in the join + * tree. */ Relids addrelids = NULL; Relids tmprelids; @@ -496,9 +498,10 @@ distribute_qual_to_rels(Query *root, Node *clause, relids = bms_union(relids, addrelids); /* Should still be a subset of current scope ... */ Assert(bms_is_subset(relids, qualscope)); + /* - * Because application of the qual will be delayed by outer join, - * we mustn't assume its vars are equal everywhere. + * Because application of the qual will be delayed by outer + * join, we mustn't assume its vars are equal everywhere. */ can_be_equijoin = false; } @@ -518,6 +521,7 @@ distribute_qual_to_rels(Query *root, Node *clause, switch (bms_membership(relids)) { case BMS_SINGLETON: + /* * There is only one relation participating in 'clause', so * 'clause' is a restriction clause for that relation. @@ -525,28 +529,29 @@ distribute_qual_to_rels(Query *root, Node *clause, rel = find_base_rel(root, bms_singleton_member(relids)); /* - * Check for a "mergejoinable" clause even though it's not a join - * clause. This is so that we can recognize that "a.x = a.y" - * makes x and y eligible to be considered equal, even when they - * belong to the same rel. Without this, we would not recognize - * that "a.x = a.y AND a.x = b.z AND a.y = c.q" allows us to - * consider z and q equal after their rels are joined. + * Check for a "mergejoinable" clause even though it's not a + * join clause. This is so that we can recognize that "a.x = + * a.y" makes x and y eligible to be considered equal, even + * when they belong to the same rel. Without this, we would + * not recognize that "a.x = a.y AND a.x = b.z AND a.y = c.q" + * allows us to consider z and q equal after their rels are + * joined. */ if (can_be_equijoin) check_mergejoinable(restrictinfo); /* - * If the clause was deduced from implied equality, check to see - * whether it is redundant with restriction clauses we already - * have for this rel. Note we cannot apply this check to - * user-written clauses, since we haven't found the canonical - * pathkey sets yet while processing user clauses. (NB: no - * comparable check is done in the join-clause case; redundancy - * will be detected when the join clause is moved into a join - * rel's restriction list.) + * If the clause was deduced from implied equality, check to + * see whether it is redundant with restriction clauses we + * already have for this rel. Note we cannot apply this check + * to user-written clauses, since we haven't found the + * canonical pathkey sets yet while processing user clauses. + * (NB: no comparable check is done in the join-clause case; + * redundancy will be detected when the join clause is moved + * into a join rel's restriction list.) */ if (!isdeduced || - !qual_is_redundant(root, restrictinfo, rel->baserestrictinfo)) + !qual_is_redundant(root, restrictinfo, rel->baserestrictinfo)) { /* Add clause to rel's restriction list */ rel->baserestrictinfo = lappend(rel->baserestrictinfo, @@ -554,13 +559,14 @@ distribute_qual_to_rels(Query *root, Node *clause, } break; case BMS_MULTIPLE: + /* - * 'clause' is a join clause, since there is more than one rel in - * the relid set. Set additional RestrictInfo fields for - * joining. First, does it look like a normal join clause, i.e., - * a binary operator relating expressions that come from distinct - * relations? If so we might be able to use it in a join - * algorithm. + * 'clause' is a join clause, since there is more than one rel + * in the relid set. Set additional RestrictInfo fields for + * joining. First, does it look like a normal join clause, + * i.e., a binary operator relating expressions that come from + * distinct relations? If so we might be able to use it in a + * join algorithm. */ if (is_opclause(clause) && length(((OpExpr *) clause)->args) == 2) { @@ -582,9 +588,9 @@ distribute_qual_to_rels(Query *root, Node *clause, * Now check for hash or mergejoinable operators. * * We don't bother setting the hashjoin info if we're not going - * to need it. We do want to know about mergejoinable ops in all - * cases, however, because we use mergejoinable ops for other - * purposes such as detecting redundant clauses. + * to need it. We do want to know about mergejoinable ops in + * all cases, however, because we use mergejoinable ops for + * other purposes such as detecting redundant clauses. */ check_mergejoinable(restrictinfo); if (enable_hashjoin) @@ -597,16 +603,18 @@ distribute_qual_to_rels(Query *root, Node *clause, /* * Add vars used in the join clause to targetlists of their - * relations, so that they will be emitted by the plan nodes that - * scan those relations (else they won't be available at the join - * node!). + * relations, so that they will be emitted by the plan nodes + * that scan those relations (else they won't be available at + * the join node!). */ add_vars_to_targetlist(root, vars, relids); break; default: + /* - * 'clause' references no rels, and therefore we have no place to - * attach it. Shouldn't get here if callers are working properly. + * 'clause' references no rels, and therefore we have no place + * to attach it. Shouldn't get here if callers are working + * properly. */ elog(ERROR, "cannot cope with variable-free clause"); break; @@ -634,7 +642,7 @@ distribute_qual_to_rels(Query *root, Node *clause, * * This processing is a consequence of transitivity of mergejoin equality: * if we have mergejoinable clauses A = B and B = C, we can deduce A = C - * (where = is an appropriate mergejoinable operator). See path/pathkeys.c + * (where = is an appropriate mergejoinable operator). See path/pathkeys.c * for more details. */ void @@ -695,8 +703,8 @@ process_implied_equality(Query *root, } /* - * Scan to see if equality is already known. If so, we're done in - * the add case, and done after removing it in the delete case. + * Scan to see if equality is already known. If so, we're done in the + * add case, and done after removing it in the delete case. */ foreach(itm, restrictlist) { @@ -719,7 +727,7 @@ process_implied_equality(Query *root, { /* delete it from local restrictinfo list */ rel1->baserestrictinfo = lremove(restrictinfo, - rel1->baserestrictinfo); + rel1->baserestrictinfo); } else { @@ -768,9 +776,9 @@ process_implied_equality(Query *root, errmsg("equality operator for types %s and %s should be mergejoinable, but isn't", format_type_be(ltype), format_type_be(rtype)))); - clause = make_opclause(oprid(eq_operator), /* opno */ - BOOLOID, /* opresulttype */ - false, /* opretset */ + clause = make_opclause(oprid(eq_operator), /* opno */ + BOOLOID, /* opresulttype */ + false, /* opretset */ (Expr *) item1, (Expr *) item2); @@ -797,9 +805,9 @@ process_implied_equality(Query *root, * too-small selectivity, not to mention wasting time at execution. * * Note: quals of the form "var = const" are never considered redundant, - * only those of the form "var = var". This is needed because when we + * only those of the form "var = var". This is needed because when we * have constants in an implied-equality set, we use a different strategy - * that suppresses all "var = var" deductions. We must therefore keep + * that suppresses all "var = var" deductions. We must therefore keep * all the "var = const" quals. */ static bool @@ -858,7 +866,8 @@ qual_is_redundant(Query *root, * left side of the new qual. We traverse the old-quals list * repeatedly to transitively expand the exprs list. If at any point * we find we can reach the right-side expr of the new qual, we are - * done. We give up when we can't expand the equalexprs list any more. + * done. We give up when we can't expand the equalexprs list any + * more. */ equalexprs = makeList1(newleft); do @@ -945,7 +954,7 @@ check_mergejoinable(RestrictInfo *restrictinfo) * info fields in the restrictinfo. * * Currently, we support hashjoin for binary opclauses where - * the operator is a hashjoinable operator. The arguments can be + * the operator is a hashjoinable operator. The arguments can be * anything --- as long as there are no volatile functions in them. */ static void |