/*------------------------------------------------------------------------- * * restrictinfo.c * RestrictInfo node manipulation routines. * * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.58 2009/04/16 20:42:16 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, Relids nullable_relids); static Expr *make_sub_restrictinfos(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids, Relids nullable_relids); static bool join_clause_is_redundant(PlannerInfo *root, RestrictInfo *rinfo, List *reference_list); /* * 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, as well as the correct value * for nullable_relids. 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, Relids nullable_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, nullable_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, nullable_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 and nullable_relids is NULL (no other * kind of 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, 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, 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, Relids nullable_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 */ restrictinfo->nullable_relids = nullable_relids; /* * 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->parent_ec = NULL; restrictinfo->eval_cost.startup = -1; restrictinfo->norm_selec = -1; restrictinfo->outer_selec = -1; restrictinfo->mergeopfamilies = NIL; restrictinfo->left_ec = NULL; restrictinfo->right_ec = NULL; restrictinfo->left_em = NULL; restrictinfo->right_em = NULL; restrictinfo->scansel_cache = NIL; restrictinfo->outer_is_left = false; 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. Likewise * for nullable_relids. * * 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, Relids nullable_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, nullable_relids)); return (Expr *) make_restrictinfo_internal(clause, make_orclause(orlist), is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids, nullable_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, nullable_relids)); return make_andclause(andlist); } else return (Expr *) make_restrictinfo_internal(clause, NULL, is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids, nullable_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); } } } /* * 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 used only for nestloop-with-inner-indexscan * joins: any clauses being checked by the index should be removed from * the qpquals list. * * "Redundant" means either equal() or derived from the same EquivalenceClass. * We have to check the latter because indxqual.c may select different derived * clauses than were selected by generate_join_implied_equalities(). * * 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) { 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)) continue; /* otherwise, add it to result list */ result = lappend(result, rinfo); } return result; } /* * join_clause_is_redundant * Test whether rinfo is redundant with any clause in reference_list. */ static bool join_clause_is_redundant(PlannerInfo *root, RestrictInfo *rinfo, List *reference_list) { ListCell *refitem; foreach(refitem, reference_list) { RestrictInfo *refrinfo = (RestrictInfo *) lfirst(refitem); /* always consider exact duplicates redundant */ if (equal(rinfo, refrinfo)) return true; /* check if derived from same EquivalenceClass */ if (rinfo->parent_ec != NULL && rinfo->parent_ec == refrinfo->parent_ec) return true; } return false; }