/*------------------------------------------------------------------------- * * restrictinfo.c * RestrictInfo node manipulation routines. * * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.49.2.1 2007/07/31 19:53:50 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "optimizer/clauses.h" #include "optimizer/cost.h" #include "optimizer/paths.h" #include "optimizer/predtest.h" #include "optimizer/restrictinfo.h" #include "optimizer/var.h" static RestrictInfo *make_restrictinfo_internal(Expr *clause, Expr *orclause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids); static Expr *make_sub_restrictinfos(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids); static RestrictInfo *join_clause_is_redundant(PlannerInfo *root, RestrictInfo *rinfo, List *reference_list, Relids outer_relids, Relids inner_relids, bool isouterjoin); /* * make_restrictinfo * * Build a RestrictInfo node containing the given subexpression. * * The is_pushed_down, outerjoin_delayed, and pseudoconstant flags for the * RestrictInfo must be supplied by the caller. required_relids can be NULL, * in which case it defaults to the actual clause contents (i.e., * clause_relids). * * We initialize fields that depend only on the given subexpression, leaving * others that depend on context (or may never be needed at all) to be filled * later. */ RestrictInfo * make_restrictinfo(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids) { /* * If it's an OR clause, build a modified copy with RestrictInfos inserted * above each subclause of the top-level AND/OR structure. */ if (or_clause((Node *) clause)) return (RestrictInfo *) make_sub_restrictinfos(clause, is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids); /* Shouldn't be an AND clause, else AND/OR flattening messed up */ Assert(!and_clause((Node *) clause)); return make_restrictinfo_internal(clause, NULL, is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids); } /* * make_restrictinfo_from_bitmapqual * * Given the bitmapqual Path structure for a bitmap indexscan, generate * RestrictInfo node(s) equivalent to the condition represented by the * indexclauses of the Path structure. * * The result is a List (effectively, implicit-AND representation) of * RestrictInfos. * * The caller must pass is_pushed_down, but we assume outerjoin_delayed * and pseudoconstant are false (no such qual should ever get into a * bitmapqual). * * If include_predicates is true, we add any partial index predicates to * the explicit index quals. When this is not true, we return a condition * that might be weaker than the actual scan represents. * * To do this through the normal make_restrictinfo() API, callers would have * to strip off the RestrictInfo nodes present in the indexclauses lists, and * then make_restrictinfo() would have to build new ones. It's better to have * a specialized routine to allow sharing of RestrictInfos. * * The qual manipulations here are much the same as in create_bitmap_subplan; * keep the two routines in sync! */ List * make_restrictinfo_from_bitmapqual(Path *bitmapqual, bool is_pushed_down, bool include_predicates) { List *result; ListCell *l; if (IsA(bitmapqual, BitmapAndPath)) { BitmapAndPath *apath = (BitmapAndPath *) bitmapqual; /* * There may well be redundant quals among the subplans, since a * top-level WHERE qual might have gotten used to form several * different index quals. We don't try exceedingly hard to eliminate * redundancies, but we do eliminate obvious duplicates by using * list_concat_unique. */ result = NIL; foreach(l, apath->bitmapquals) { List *sublist; sublist = make_restrictinfo_from_bitmapqual((Path *) lfirst(l), is_pushed_down, include_predicates); result = list_concat_unique(result, sublist); } } else if (IsA(bitmapqual, BitmapOrPath)) { BitmapOrPath *opath = (BitmapOrPath *) bitmapqual; List *withris = NIL; List *withoutris = NIL; /* * Here, we only detect qual-free subplans. A qual-free subplan would * cause us to generate "... OR true ..." which we may as well reduce * to just "true". We do not try to eliminate redundant subclauses * because (a) it's not as likely as in the AND case, and (b) we might * well be working with hundreds or even thousands of OR conditions, * perhaps from a long IN list. The performance of list_append_unique * would be unacceptable. */ foreach(l, opath->bitmapquals) { List *sublist; sublist = make_restrictinfo_from_bitmapqual((Path *) lfirst(l), is_pushed_down, include_predicates); if (sublist == NIL) { /* * If we find a qual-less subscan, it represents a constant * TRUE, and hence the OR result is also constant TRUE, so we * can stop here. */ return NIL; } /* * If the sublist contains multiple RestrictInfos, we create an * AND subclause. If there's just one, we have to check if it's * an OR clause, and if so flatten it to preserve AND/OR flatness * of our output. * * We construct lists with and without sub-RestrictInfos, so as * not to have to regenerate duplicate RestrictInfos below. */ if (list_length(sublist) > 1) { withris = lappend(withris, make_andclause(sublist)); sublist = get_actual_clauses(sublist); withoutris = lappend(withoutris, make_andclause(sublist)); } else { RestrictInfo *subri = (RestrictInfo *) linitial(sublist); Assert(IsA(subri, RestrictInfo)); if (restriction_is_or_clause(subri)) { BoolExpr *subor = (BoolExpr *) subri->orclause; Assert(or_clause((Node *) subor)); withris = list_concat(withris, list_copy(subor->args)); subor = (BoolExpr *) subri->clause; Assert(or_clause((Node *) subor)); withoutris = list_concat(withoutris, list_copy(subor->args)); } else { withris = lappend(withris, subri); withoutris = lappend(withoutris, subri->clause); } } } /* * Avoid generating one-element ORs, which could happen due to * redundancy elimination or ScalarArrayOpExpr quals. */ if (list_length(withris) <= 1) result = withris; else { /* Here's the magic part not available to outside callers */ result = list_make1(make_restrictinfo_internal(make_orclause(withoutris), make_orclause(withris), is_pushed_down, false, false, NULL)); } } else if (IsA(bitmapqual, IndexPath)) { IndexPath *ipath = (IndexPath *) bitmapqual; result = list_copy(ipath->indexclauses); if (include_predicates && ipath->indexinfo->indpred != NIL) { foreach(l, ipath->indexinfo->indpred) { Expr *pred = (Expr *) lfirst(l); /* * We know that the index predicate must have been implied by * the query condition as a whole, but it may or may not be * implied by the conditions that got pushed into the * bitmapqual. Avoid generating redundant conditions. */ if (!predicate_implied_by(list_make1(pred), result)) result = lappend(result, make_restrictinfo(pred, is_pushed_down, false, false, NULL)); } } } else { elog(ERROR, "unrecognized node type: %d", nodeTag(bitmapqual)); result = NIL; /* keep compiler quiet */ } return result; } /* * make_restrictinfo_internal * * Common code for the main entry points and the recursive cases. */ static RestrictInfo * make_restrictinfo_internal(Expr *clause, Expr *orclause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids) { RestrictInfo *restrictinfo = makeNode(RestrictInfo); restrictinfo->clause = clause; restrictinfo->orclause = orclause; restrictinfo->is_pushed_down = is_pushed_down; restrictinfo->outerjoin_delayed = outerjoin_delayed; restrictinfo->pseudoconstant = pseudoconstant; restrictinfo->can_join = false; /* may get set below */ /* * If it's a binary opclause, set up left/right relids info. In any case * set up the total clause relids info. */ if (is_opclause(clause) && list_length(((OpExpr *) clause)->args) == 2) { restrictinfo->left_relids = pull_varnos(get_leftop(clause)); restrictinfo->right_relids = pull_varnos(get_rightop(clause)); restrictinfo->clause_relids = bms_union(restrictinfo->left_relids, restrictinfo->right_relids); /* * 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. Note that this is a * purely syntactic test that is made regardless of context. */ if (!bms_is_empty(restrictinfo->left_relids) && !bms_is_empty(restrictinfo->right_relids) && !bms_overlap(restrictinfo->left_relids, restrictinfo->right_relids)) { restrictinfo->can_join = true; /* pseudoconstant should certainly not be true */ Assert(!restrictinfo->pseudoconstant); } } else { /* Not a binary opclause, so mark left/right relid sets as empty */ restrictinfo->left_relids = NULL; restrictinfo->right_relids = NULL; /* and get the total relid set the hard way */ restrictinfo->clause_relids = pull_varnos((Node *) clause); } /* required_relids defaults to clause_relids */ if (required_relids != NULL) restrictinfo->required_relids = required_relids; else restrictinfo->required_relids = restrictinfo->clause_relids; /* * Fill in all the cacheable fields with "not yet set" markers. None of * these will be computed until/unless needed. Note in particular that we * don't mark a binary opclause as mergejoinable or hashjoinable here; * that happens only if it appears in the right context (top level of a * joinclause list). */ restrictinfo->eval_cost.startup = -1; restrictinfo->this_selec = -1; restrictinfo->mergejoinoperator = InvalidOid; restrictinfo->left_sortop = InvalidOid; restrictinfo->right_sortop = InvalidOid; restrictinfo->left_pathkey = NIL; restrictinfo->right_pathkey = NIL; restrictinfo->left_mergescansel = -1; restrictinfo->right_mergescansel = -1; restrictinfo->hashjoinoperator = InvalidOid; restrictinfo->left_bucketsize = -1; restrictinfo->right_bucketsize = -1; return restrictinfo; } /* * Recursively insert sub-RestrictInfo nodes into a boolean expression. * * We put RestrictInfos above simple (non-AND/OR) clauses and above * sub-OR clauses, but not above sub-AND clauses, because there's no need. * This may seem odd but it is closely related to the fact that we use * implicit-AND lists at top level of RestrictInfo lists. Only ORs and * simple clauses are valid RestrictInfos. * * The same is_pushed_down, outerjoin_delayed, and pseudoconstant flag * values can be applied to all RestrictInfo nodes in the result. * * The given required_relids are attached to our top-level output, * but any OR-clause constituents are allowed to default to just the * contained rels. */ static Expr * make_sub_restrictinfos(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids) { if (or_clause((Node *) clause)) { List *orlist = NIL; ListCell *temp; foreach(temp, ((BoolExpr *) clause)->args) orlist = lappend(orlist, make_sub_restrictinfos(lfirst(temp), is_pushed_down, outerjoin_delayed, pseudoconstant, NULL)); return (Expr *) make_restrictinfo_internal(clause, make_orclause(orlist), is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids); } else if (and_clause((Node *) clause)) { List *andlist = NIL; ListCell *temp; foreach(temp, ((BoolExpr *) clause)->args) andlist = lappend(andlist, make_sub_restrictinfos(lfirst(temp), is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids)); return make_andclause(andlist); } else return (Expr *) make_restrictinfo_internal(clause, NULL, is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids); } /* * restriction_is_or_clause * * Returns t iff the restrictinfo node contains an 'or' clause. */ bool restriction_is_or_clause(RestrictInfo *restrictinfo) { if (restrictinfo->orclause != NULL) return true; else return false; } /* * get_actual_clauses * * Returns a list containing the bare clauses from 'restrictinfo_list'. * * This is only to be used in cases where none of the RestrictInfos can * be pseudoconstant clauses (for instance, it's OK on indexqual lists). */ List * get_actual_clauses(List *restrictinfo_list) { List *result = NIL; ListCell *l; foreach(l, restrictinfo_list) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(l); Assert(IsA(rinfo, RestrictInfo)); Assert(!rinfo->pseudoconstant); result = lappend(result, rinfo->clause); } return result; } /* * extract_actual_clauses * * Extract bare clauses from 'restrictinfo_list', returning either the * regular ones or the pseudoconstant ones per 'pseudoconstant'. */ List * extract_actual_clauses(List *restrictinfo_list, bool pseudoconstant) { List *result = NIL; ListCell *l; foreach(l, restrictinfo_list) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(l); Assert(IsA(rinfo, RestrictInfo)); if (rinfo->pseudoconstant == pseudoconstant) result = lappend(result, rinfo->clause); } return result; } /* * extract_actual_join_clauses * * Extract bare clauses from 'restrictinfo_list', separating those that * syntactically match the join level from those that were pushed down. * Pseudoconstant clauses are excluded from the results. * * This is only used at outer joins, since for plain joins we don't care * about pushed-down-ness. */ void extract_actual_join_clauses(List *restrictinfo_list, List **joinquals, List **otherquals) { ListCell *l; *joinquals = NIL; *otherquals = NIL; foreach(l, restrictinfo_list) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(l); Assert(IsA(rinfo, RestrictInfo)); if (rinfo->is_pushed_down) { if (!rinfo->pseudoconstant) *otherquals = lappend(*otherquals, rinfo->clause); } else { /* joinquals shouldn't have been marked pseudoconstant */ Assert(!rinfo->pseudoconstant); *joinquals = lappend(*joinquals, rinfo->clause); } } } /* * remove_redundant_join_clauses * * Given a list of RestrictInfo clauses that are to be applied in a join, * remove any duplicate or redundant clauses. * * We must eliminate duplicates when forming the restrictlist for a joinrel, * since we will see many of the same clauses arriving from both input * relations. Also, if a clause is a mergejoinable clause, it's possible that * it is redundant with previous clauses (see optimizer/README for * discussion). We detect that case and omit the redundant clause from the * result list. * * The result is a fresh List, but it points to the same member nodes * as were in the input. */ List * remove_redundant_join_clauses(PlannerInfo *root, List *restrictinfo_list, Relids outer_relids, Relids inner_relids, bool isouterjoin) { List *result = NIL; ListCell *item; QualCost cost; /* * If there are any redundant clauses, we want to eliminate the ones that * are more expensive in favor of the ones that are less so. Run * cost_qual_eval() to ensure the eval_cost fields are set up. */ cost_qual_eval(&cost, restrictinfo_list); /* * We don't have enough knowledge yet to be able to estimate the number of * times a clause might be evaluated, so it's hard to weight the startup * and per-tuple costs appropriately. For now just weight 'em the same. */ #define CLAUSECOST(r) ((r)->eval_cost.startup + (r)->eval_cost.per_tuple) foreach(item, restrictinfo_list) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(item); RestrictInfo *prevrinfo; /* is it redundant with any prior clause? */ prevrinfo = join_clause_is_redundant(root, rinfo, result, outer_relids, inner_relids, isouterjoin); if (prevrinfo == NULL) { /* no, so add it to result list */ result = lappend(result, rinfo); } else if (CLAUSECOST(rinfo) < CLAUSECOST(prevrinfo)) { /* keep this one, drop the previous one */ result = list_delete_ptr(result, prevrinfo); result = lappend(result, rinfo); } /* else, drop this one */ } return result; } /* * select_nonredundant_join_clauses * * Given a list of RestrictInfo clauses that are to be applied in a join, * select the ones that are not redundant with any clause in the * reference_list. * * This is similar to remove_redundant_join_clauses, but we are looking for * redundancies with a separate list of clauses (i.e., clauses that have * already been applied below the join itself). * * Note that we assume the given restrictinfo_list has already been checked * for local redundancies, so we don't check again. */ List * select_nonredundant_join_clauses(PlannerInfo *root, List *restrictinfo_list, List *reference_list, Relids outer_relids, Relids inner_relids, bool isouterjoin) { List *result = NIL; ListCell *item; foreach(item, restrictinfo_list) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(item); /* drop it if redundant with any reference clause */ if (join_clause_is_redundant(root, rinfo, reference_list, outer_relids, inner_relids, isouterjoin) != NULL) continue; /* otherwise, add it to result list */ result = lappend(result, rinfo); } return result; } /* * join_clause_is_redundant * If rinfo is redundant with any clause in reference_list, * return one such clause; otherwise return NULL. * * This is the guts of both remove_redundant_join_clauses and * select_nonredundant_join_clauses. See the docs above for motivation. * * We can detect redundant mergejoinable clauses very cheaply by using their * left and right pathkeys, which uniquely identify the sets of equijoined * variables in question. All the members of a pathkey set that are in the * left relation have already been forced to be equal; likewise for those in * the right relation. So, we need to have only one clause that checks * equality between any set member on the left and any member on the right; * by transitivity, all the rest are then equal. * * However, clauses that are of the form "var expr = const expr" cannot be * eliminated as redundant. This is because when there are const expressions * in a pathkey set, generate_implied_equalities() suppresses "var = var" * clauses in favor of "var = const" clauses. We cannot afford to drop any * of the latter, even though they might seem redundant by the pathkey * membership test. * * Also, we cannot eliminate clauses wherein one side mentions vars from * both relations, as in "WHERE t1.f1 = t2.f1 AND t1.f1 = t1.f2 - t2.f2". * In this example, "t1.f2 - t2.f2" could not have been computed at all * before forming the join of t1 and t2, so it certainly wasn't constrained * earlier. * * Weird special case: if we have two clauses that seem redundant * except one is pushed down into an outer join and the other isn't, * then they're not really redundant, because one constrains the * joined rows after addition of null fill rows, and the other doesn't. */ static RestrictInfo * join_clause_is_redundant(PlannerInfo *root, RestrictInfo *rinfo, List *reference_list, Relids outer_relids, Relids inner_relids, bool isouterjoin) { ListCell *refitem; /* always consider exact duplicates redundant */ foreach(refitem, reference_list) { RestrictInfo *refrinfo = (RestrictInfo *) lfirst(refitem); if (equal(rinfo, refrinfo)) return refrinfo; } /* check for redundant merge clauses */ if (rinfo->mergejoinoperator != InvalidOid) { /* do the cheap test first: is it a "var = const" clause? */ if (bms_is_empty(rinfo->left_relids) || bms_is_empty(rinfo->right_relids)) return NULL; /* var = const, so not redundant */ /* check for either side mentioning both rels */ if (bms_overlap(rinfo->left_relids, outer_relids) && bms_overlap(rinfo->left_relids, inner_relids)) return NULL; /* clause LHS uses both, so not redundant */ if (bms_overlap(rinfo->right_relids, outer_relids) && bms_overlap(rinfo->right_relids, inner_relids)) return NULL; /* clause RHS uses both, so not redundant */ cache_mergeclause_pathkeys(root, rinfo); foreach(refitem, reference_list) { RestrictInfo *refrinfo = (RestrictInfo *) lfirst(refitem); if (refrinfo->mergejoinoperator != InvalidOid) { cache_mergeclause_pathkeys(root, refrinfo); if (rinfo->left_pathkey == refrinfo->left_pathkey && rinfo->right_pathkey == refrinfo->right_pathkey && (rinfo->is_pushed_down == refrinfo->is_pushed_down || !isouterjoin)) { /* Yup, it's redundant */ return refrinfo; } } } } /* otherwise, not redundant */ return NULL; }