/*------------------------------------------------------------------------- * * equivclass.c * Routines for managing EquivalenceClasses * * See src/backend/optimizer/README for discussion of EquivalenceClasses. * * * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION * src/backend/optimizer/path/equivclass.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include "access/stratnum.h" #include "catalog/pg_type.h" #include "nodes/makefuncs.h" #include "nodes/nodeFuncs.h" #include "optimizer/appendinfo.h" #include "optimizer/clauses.h" #include "optimizer/optimizer.h" #include "optimizer/pathnode.h" #include "optimizer/paths.h" #include "optimizer/planmain.h" #include "optimizer/restrictinfo.h" #include "utils/lsyscache.h" static EquivalenceMember *add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids, Relids nullable_relids, bool is_child, Oid datatype); static bool is_exprlist_member(Expr *node, List *exprs); static void generate_base_implied_equalities_const(PlannerInfo *root, EquivalenceClass *ec); static void generate_base_implied_equalities_no_const(PlannerInfo *root, EquivalenceClass *ec); static void generate_base_implied_equalities_broken(PlannerInfo *root, EquivalenceClass *ec); static List *generate_join_implied_equalities_normal(PlannerInfo *root, EquivalenceClass *ec, Relids join_relids, Relids outer_relids, Relids inner_relids); static List *generate_join_implied_equalities_broken(PlannerInfo *root, EquivalenceClass *ec, Relids nominal_join_relids, Relids outer_relids, Relids nominal_inner_relids, RelOptInfo *inner_rel); static Oid select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype); static RestrictInfo *create_join_clause(PlannerInfo *root, EquivalenceClass *ec, Oid opno, EquivalenceMember *leftem, EquivalenceMember *rightem, EquivalenceClass *parent_ec); static bool reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo, bool outer_on_left); static bool reconsider_full_join_clause(PlannerInfo *root, RestrictInfo *rinfo); static Bitmapset *get_eclass_indexes_for_relids(PlannerInfo *root, Relids relids); static Bitmapset *get_common_eclass_indexes(PlannerInfo *root, Relids relids1, Relids relids2); /* * process_equivalence * The given clause has a mergejoinable operator and can be applied without * any delay by an outer join, so its two sides can be considered equal * anywhere they are both computable; moreover that equality can be * extended transitively. Record this knowledge in the EquivalenceClass * data structure, if applicable. Returns true if successful, false if not * (in which case caller should treat the clause as ordinary, not an * equivalence). * * In some cases, although we cannot convert a clause into EquivalenceClass * knowledge, we can still modify it to a more useful form than the original. * Then, *p_restrictinfo will be replaced by a new RestrictInfo, which is what * the caller should use for further processing. * * If below_outer_join is true, then the clause was found below the nullable * side of an outer join, so its sides might validly be both NULL rather than * strictly equal. We can still deduce equalities in such cases, but we take * care to mark an EquivalenceClass if it came from any such clauses. Also, * we have to check that both sides are either pseudo-constants or strict * functions of Vars, else they might not both go to NULL above the outer * join. (This is the main reason why we need a failure return. It's more * convenient to check this case here than at the call sites...) * * We also reject proposed equivalence clauses if they contain leaky functions * and have security_level above zero. The EC evaluation rules require us to * apply certain tests at certain joining levels, and we can't tolerate * delaying any test on security_level grounds. By rejecting candidate clauses * that might require security delays, we ensure it's safe to apply an EC * clause as soon as it's supposed to be applied. * * On success return, we have also initialized the clause's left_ec/right_ec * fields to point to the EquivalenceClass representing it. This saves lookup * effort later. * * Note: constructing merged EquivalenceClasses is a standard UNION-FIND * problem, for which there exist better data structures than simple lists. * If this code ever proves to be a bottleneck then it could be sped up --- * but for now, simple is beautiful. * * Note: this is only called during planner startup, not during GEQO * exploration, so we need not worry about whether we're in the right * memory context. */ bool process_equivalence(PlannerInfo *root, RestrictInfo **p_restrictinfo, bool below_outer_join) { RestrictInfo *restrictinfo = *p_restrictinfo; Expr *clause = restrictinfo->clause; Oid opno, collation, item1_type, item2_type; Expr *item1; Expr *item2; Relids item1_relids, item2_relids, item1_nullable_relids, item2_nullable_relids; List *opfamilies; EquivalenceClass *ec1, *ec2; EquivalenceMember *em1, *em2; ListCell *lc1; int ec2_idx; /* Should not already be marked as having generated an eclass */ Assert(restrictinfo->left_ec == NULL); Assert(restrictinfo->right_ec == NULL); /* Reject if it is potentially postponable by security considerations */ if (restrictinfo->security_level > 0 && !restrictinfo->leakproof) return false; /* Extract info from given clause */ Assert(is_opclause(clause)); opno = ((OpExpr *) clause)->opno; collation = ((OpExpr *) clause)->inputcollid; item1 = (Expr *) get_leftop(clause); item2 = (Expr *) get_rightop(clause); item1_relids = restrictinfo->left_relids; item2_relids = restrictinfo->right_relids; /* * Ensure both input expressions expose the desired collation (their types * should be OK already); see comments for canonicalize_ec_expression. */ item1 = canonicalize_ec_expression(item1, exprType((Node *) item1), collation); item2 = canonicalize_ec_expression(item2, exprType((Node *) item2), collation); /* * Clauses of the form X=X cannot be translated into EquivalenceClasses. * We'd either end up with a single-entry EC, losing the knowledge that * the clause was present at all, or else make an EC with duplicate * entries, causing other issues. */ if (equal(item1, item2)) { /* * If the operator is strict, then the clause can be treated as just * "X IS NOT NULL". (Since we know we are considering a top-level * qual, we can ignore the difference between FALSE and NULL results.) * It's worth making the conversion because we'll typically get a much * better selectivity estimate than we would for X=X. * * If the operator is not strict, we can't be sure what it will do * with NULLs, so don't attempt to optimize it. */ set_opfuncid((OpExpr *) clause); if (func_strict(((OpExpr *) clause)->opfuncid)) { NullTest *ntest = makeNode(NullTest); ntest->arg = item1; ntest->nulltesttype = IS_NOT_NULL; ntest->argisrow = false; /* correct even if composite arg */ ntest->location = -1; *p_restrictinfo = make_restrictinfo(root, (Expr *) ntest, restrictinfo->is_pushed_down, restrictinfo->outerjoin_delayed, restrictinfo->pseudoconstant, restrictinfo->security_level, NULL, restrictinfo->outer_relids, restrictinfo->nullable_relids); } return false; } /* * If below outer join, check for strictness, else reject. */ if (below_outer_join) { if (!bms_is_empty(item1_relids) && contain_nonstrict_functions((Node *) item1)) return false; /* LHS is non-strict but not constant */ if (!bms_is_empty(item2_relids) && contain_nonstrict_functions((Node *) item2)) return false; /* RHS is non-strict but not constant */ } /* Calculate nullable-relid sets for each side of the clause */ item1_nullable_relids = bms_intersect(item1_relids, restrictinfo->nullable_relids); item2_nullable_relids = bms_intersect(item2_relids, restrictinfo->nullable_relids); /* * We use the declared input types of the operator, not exprType() of the * inputs, as the nominal datatypes for opfamily lookup. This presumes * that btree operators are always registered with amoplefttype and * amoprighttype equal to their declared input types. We will need this * info anyway to build EquivalenceMember nodes, and by extracting it now * we can use type comparisons to short-circuit some equal() tests. */ op_input_types(opno, &item1_type, &item2_type); opfamilies = restrictinfo->mergeopfamilies; /* * Sweep through the existing EquivalenceClasses looking for matches to * item1 and item2. These are the possible outcomes: * * 1. We find both in the same EC. The equivalence is already known, so * there's nothing to do. * * 2. We find both in different ECs. Merge the two ECs together. * * 3. We find just one. Add the other to its EC. * * 4. We find neither. Make a new, two-entry EC. * * Note: since all ECs are built through this process or the similar * search in get_eclass_for_sort_expr(), it's impossible that we'd match * an item in more than one existing nonvolatile EC. So it's okay to stop * at the first match. */ ec1 = ec2 = NULL; em1 = em2 = NULL; ec2_idx = -1; foreach(lc1, root->eq_classes) { EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1); ListCell *lc2; /* Never match to a volatile EC */ if (cur_ec->ec_has_volatile) continue; /* * The collation has to match; check this first since it's cheaper * than the opfamily comparison. */ if (collation != cur_ec->ec_collation) continue; /* * A "match" requires matching sets of btree opfamilies. Use of * equal() for this test has implications discussed in the comments * for get_mergejoin_opfamilies(). */ if (!equal(opfamilies, cur_ec->ec_opfamilies)) continue; foreach(lc2, cur_ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2); Assert(!cur_em->em_is_child); /* no children yet */ /* * If below an outer join, don't match constants: they're not as * constant as they look. */ if ((below_outer_join || cur_ec->ec_below_outer_join) && cur_em->em_is_const) continue; if (!ec1 && item1_type == cur_em->em_datatype && equal(item1, cur_em->em_expr)) { ec1 = cur_ec; em1 = cur_em; if (ec2) break; } if (!ec2 && item2_type == cur_em->em_datatype && equal(item2, cur_em->em_expr)) { ec2 = cur_ec; ec2_idx = foreach_current_index(lc1); em2 = cur_em; if (ec1) break; } } if (ec1 && ec2) break; } /* Sweep finished, what did we find? */ if (ec1 && ec2) { /* If case 1, nothing to do, except add to sources */ if (ec1 == ec2) { ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo); ec1->ec_below_outer_join |= below_outer_join; ec1->ec_min_security = Min(ec1->ec_min_security, restrictinfo->security_level); ec1->ec_max_security = Max(ec1->ec_max_security, restrictinfo->security_level); /* mark the RI as associated with this eclass */ restrictinfo->left_ec = ec1; restrictinfo->right_ec = ec1; /* mark the RI as usable with this pair of EMs */ restrictinfo->left_em = em1; restrictinfo->right_em = em2; return true; } /* * Case 2: need to merge ec1 and ec2. This should never happen after * the ECs have reached canonical state; otherwise, pathkeys could be * rendered non-canonical by the merge, and relation eclass indexes * would get broken by removal of an eq_classes list entry. */ if (root->ec_merging_done) elog(ERROR, "too late to merge equivalence classes"); /* * We add ec2's items to ec1, then set ec2's ec_merged link to point * to ec1 and remove ec2 from the eq_classes list. We cannot simply * delete ec2 because that could leave dangling pointers in existing * PathKeys. We leave it behind with a link so that the merged EC can * be found. */ ec1->ec_members = list_concat(ec1->ec_members, ec2->ec_members); ec1->ec_sources = list_concat(ec1->ec_sources, ec2->ec_sources); ec1->ec_derives = list_concat(ec1->ec_derives, ec2->ec_derives); ec1->ec_relids = bms_join(ec1->ec_relids, ec2->ec_relids); ec1->ec_has_const |= ec2->ec_has_const; /* can't need to set has_volatile */ ec1->ec_below_outer_join |= ec2->ec_below_outer_join; ec1->ec_min_security = Min(ec1->ec_min_security, ec2->ec_min_security); ec1->ec_max_security = Max(ec1->ec_max_security, ec2->ec_max_security); ec2->ec_merged = ec1; root->eq_classes = list_delete_nth_cell(root->eq_classes, ec2_idx); /* just to avoid debugging confusion w/ dangling pointers: */ ec2->ec_members = NIL; ec2->ec_sources = NIL; ec2->ec_derives = NIL; ec2->ec_relids = NULL; ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo); ec1->ec_below_outer_join |= below_outer_join; ec1->ec_min_security = Min(ec1->ec_min_security, restrictinfo->security_level); ec1->ec_max_security = Max(ec1->ec_max_security, restrictinfo->security_level); /* mark the RI as associated with this eclass */ restrictinfo->left_ec = ec1; restrictinfo->right_ec = ec1; /* mark the RI as usable with this pair of EMs */ restrictinfo->left_em = em1; restrictinfo->right_em = em2; } else if (ec1) { /* Case 3: add item2 to ec1 */ em2 = add_eq_member(ec1, item2, item2_relids, item2_nullable_relids, false, item2_type); ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo); ec1->ec_below_outer_join |= below_outer_join; ec1->ec_min_security = Min(ec1->ec_min_security, restrictinfo->security_level); ec1->ec_max_security = Max(ec1->ec_max_security, restrictinfo->security_level); /* mark the RI as associated with this eclass */ restrictinfo->left_ec = ec1; restrictinfo->right_ec = ec1; /* mark the RI as usable with this pair of EMs */ restrictinfo->left_em = em1; restrictinfo->right_em = em2; } else if (ec2) { /* Case 3: add item1 to ec2 */ em1 = add_eq_member(ec2, item1, item1_relids, item1_nullable_relids, false, item1_type); ec2->ec_sources = lappend(ec2->ec_sources, restrictinfo); ec2->ec_below_outer_join |= below_outer_join; ec2->ec_min_security = Min(ec2->ec_min_security, restrictinfo->security_level); ec2->ec_max_security = Max(ec2->ec_max_security, restrictinfo->security_level); /* mark the RI as associated with this eclass */ restrictinfo->left_ec = ec2; restrictinfo->right_ec = ec2; /* mark the RI as usable with this pair of EMs */ restrictinfo->left_em = em1; restrictinfo->right_em = em2; } else { /* Case 4: make a new, two-entry EC */ EquivalenceClass *ec = makeNode(EquivalenceClass); ec->ec_opfamilies = opfamilies; ec->ec_collation = collation; ec->ec_members = NIL; ec->ec_sources = list_make1(restrictinfo); ec->ec_derives = NIL; ec->ec_relids = NULL; ec->ec_has_const = false; ec->ec_has_volatile = false; ec->ec_below_outer_join = below_outer_join; ec->ec_broken = false; ec->ec_sortref = 0; ec->ec_min_security = restrictinfo->security_level; ec->ec_max_security = restrictinfo->security_level; ec->ec_merged = NULL; em1 = add_eq_member(ec, item1, item1_relids, item1_nullable_relids, false, item1_type); em2 = add_eq_member(ec, item2, item2_relids, item2_nullable_relids, false, item2_type); root->eq_classes = lappend(root->eq_classes, ec); /* mark the RI as associated with this eclass */ restrictinfo->left_ec = ec; restrictinfo->right_ec = ec; /* mark the RI as usable with this pair of EMs */ restrictinfo->left_em = em1; restrictinfo->right_em = em2; } return true; } /* * canonicalize_ec_expression * * This function ensures that the expression exposes the expected type and * collation, so that it will be equal() to other equivalence-class expressions * that it ought to be equal() to. * * The rule for datatypes is that the exposed type should match what it would * be for an input to an operator of the EC's opfamilies; which is usually * the declared input type of the operator, but in the case of polymorphic * operators no relabeling is wanted (compare the behavior of parse_coerce.c). * Expressions coming in from quals will generally have the right type * already, but expressions coming from indexkeys may not (because they are * represented without any explicit relabel in pg_index), and the same problem * occurs for sort expressions (because the parser is likewise cavalier about * putting relabels on them). Such cases will be binary-compatible with the * real operators, so adding a RelabelType is sufficient. * * Also, the expression's exposed collation must match the EC's collation. * This is important because in comparisons like "foo < bar COLLATE baz", * only one of the expressions has the correct exposed collation as we receive * it from the parser. Forcing both of them to have it ensures that all * variant spellings of such a construct behave the same. Again, we can * stick on a RelabelType to force the right exposed collation. (It might * work to not label the collation at all in EC members, but this is risky * since some parts of the system expect exprCollation() to deliver the * right answer for a sort key.) */ Expr * canonicalize_ec_expression(Expr *expr, Oid req_type, Oid req_collation) { Oid expr_type = exprType((Node *) expr); /* * For a polymorphic-input-type opclass, just keep the same exposed type. * RECORD opclasses work like polymorphic-type ones for this purpose. */ if (IsPolymorphicType(req_type) || req_type == RECORDOID) req_type = expr_type; /* * No work if the expression exposes the right type/collation already. */ if (expr_type != req_type || exprCollation((Node *) expr) != req_collation) { /* * If we have to change the type of the expression, set typmod to -1, * since the new type may not have the same typmod interpretation. * When we only have to change collation, preserve the exposed typmod. */ int32 req_typmod; if (expr_type != req_type) req_typmod = -1; else req_typmod = exprTypmod((Node *) expr); /* * Use applyRelabelType so that we preserve const-flatness. This is * important since eval_const_expressions has already been applied. */ expr = (Expr *) applyRelabelType((Node *) expr, req_type, req_typmod, req_collation, COERCE_IMPLICIT_CAST, -1, false); } return expr; } /* * add_eq_member - build a new EquivalenceMember and add it to an EC */ static EquivalenceMember * add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids, Relids nullable_relids, bool is_child, Oid datatype) { EquivalenceMember *em = makeNode(EquivalenceMember); em->em_expr = expr; em->em_relids = relids; em->em_nullable_relids = nullable_relids; em->em_is_const = false; em->em_is_child = is_child; em->em_datatype = datatype; if (bms_is_empty(relids)) { /* * No Vars, assume it's a pseudoconstant. This is correct for entries * generated from process_equivalence(), because a WHERE clause can't * contain aggregates or SRFs, and non-volatility was checked before * process_equivalence() ever got called. But * get_eclass_for_sort_expr() has to work harder. We put the tests * there not here to save cycles in the equivalence case. */ Assert(!is_child); em->em_is_const = true; ec->ec_has_const = true; /* it can't affect ec_relids */ } else if (!is_child) /* child members don't add to ec_relids */ { ec->ec_relids = bms_add_members(ec->ec_relids, relids); } ec->ec_members = lappend(ec->ec_members, em); return em; } /* * get_eclass_for_sort_expr * Given an expression and opfamily/collation info, find an existing * equivalence class it is a member of; if none, optionally build a new * single-member EquivalenceClass for it. * * expr is the expression, and nullable_relids is the set of base relids * that are potentially nullable below it. We actually only care about * the set of such relids that are used in the expression; but for caller * convenience, we perform that intersection step here. The caller need * only be sure that nullable_relids doesn't omit any nullable rels that * might appear in the expr. * * sortref is the SortGroupRef of the originating SortGroupClause, if any, * or zero if not. (It should never be zero if the expression is volatile!) * * If rel is not NULL, it identifies a specific relation we're considering * a path for, and indicates that child EC members for that relation can be * considered. Otherwise child members are ignored. (Note: since child EC * members aren't guaranteed unique, a non-NULL value means that there could * be more than one EC that matches the expression; if so it's order-dependent * which one you get. This is annoying but it only happens in corner cases, * so for now we live with just reporting the first match. See also * generate_implied_equalities_for_column and match_pathkeys_to_index.) * * If create_it is true, we'll build a new EquivalenceClass when there is no * match. If create_it is false, we just return NULL when no match. * * This can be used safely both before and after EquivalenceClass merging; * since it never causes merging it does not invalidate any existing ECs * or PathKeys. However, ECs added after path generation has begun are * of limited usefulness, so usually it's best to create them beforehand. * * Note: opfamilies must be chosen consistently with the way * process_equivalence() would do; that is, generated from a mergejoinable * equality operator. Else we might fail to detect valid equivalences, * generating poor (but not incorrect) plans. */ EquivalenceClass * get_eclass_for_sort_expr(PlannerInfo *root, Expr *expr, Relids nullable_relids, List *opfamilies, Oid opcintype, Oid collation, Index sortref, Relids rel, bool create_it) { Relids expr_relids; EquivalenceClass *newec; EquivalenceMember *newem; ListCell *lc1; MemoryContext oldcontext; /* * Ensure the expression exposes the correct type and collation. */ expr = canonicalize_ec_expression(expr, opcintype, collation); /* * Scan through the existing EquivalenceClasses for a match */ foreach(lc1, root->eq_classes) { EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1); ListCell *lc2; /* * Never match to a volatile EC, except when we are looking at another * reference to the same volatile SortGroupClause. */ if (cur_ec->ec_has_volatile && (sortref == 0 || sortref != cur_ec->ec_sortref)) continue; if (collation != cur_ec->ec_collation) continue; if (!equal(opfamilies, cur_ec->ec_opfamilies)) continue; foreach(lc2, cur_ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2); /* * Ignore child members unless they match the request. */ if (cur_em->em_is_child && !bms_equal(cur_em->em_relids, rel)) continue; /* * If below an outer join, don't match constants: they're not as * constant as they look. */ if (cur_ec->ec_below_outer_join && cur_em->em_is_const) continue; if (opcintype == cur_em->em_datatype && equal(expr, cur_em->em_expr)) return cur_ec; /* Match! */ } } /* No match; does caller want a NULL result? */ if (!create_it) return NULL; /* * OK, build a new single-member EC * * Here, we must be sure that we construct the EC in the right context. */ oldcontext = MemoryContextSwitchTo(root->planner_cxt); newec = makeNode(EquivalenceClass); newec->ec_opfamilies = list_copy(opfamilies); newec->ec_collation = collation; newec->ec_members = NIL; newec->ec_sources = NIL; newec->ec_derives = NIL; newec->ec_relids = NULL; newec->ec_has_const = false; newec->ec_has_volatile = contain_volatile_functions((Node *) expr); newec->ec_below_outer_join = false; newec->ec_broken = false; newec->ec_sortref = sortref; newec->ec_min_security = UINT_MAX; newec->ec_max_security = 0; newec->ec_merged = NULL; if (newec->ec_has_volatile && sortref == 0) /* should not happen */ elog(ERROR, "volatile EquivalenceClass has no sortref"); /* * Get the precise set of nullable relids appearing in the expression. */ expr_relids = pull_varnos(root, (Node *) expr); nullable_relids = bms_intersect(nullable_relids, expr_relids); newem = add_eq_member(newec, copyObject(expr), expr_relids, nullable_relids, false, opcintype); /* * add_eq_member doesn't check for volatile functions, set-returning * functions, aggregates, or window functions, but such could appear in * sort expressions; so we have to check whether its const-marking was * correct. */ if (newec->ec_has_const) { if (newec->ec_has_volatile || expression_returns_set((Node *) expr) || contain_agg_clause((Node *) expr) || contain_window_function((Node *) expr)) { newec->ec_has_const = false; newem->em_is_const = false; } } root->eq_classes = lappend(root->eq_classes, newec); /* * If EC merging is already complete, we have to mop up by adding the new * EC to the eclass_indexes of the relation(s) mentioned in it. */ if (root->ec_merging_done) { int ec_index = list_length(root->eq_classes) - 1; int i = -1; while ((i = bms_next_member(newec->ec_relids, i)) > 0) { RelOptInfo *rel = root->simple_rel_array[i]; Assert(rel->reloptkind == RELOPT_BASEREL || rel->reloptkind == RELOPT_DEADREL); rel->eclass_indexes = bms_add_member(rel->eclass_indexes, ec_index); } } MemoryContextSwitchTo(oldcontext); return newec; } /* * find_ec_member_matching_expr * Locate an EquivalenceClass member matching the given expr, if any; * return NULL if no match. * * "Matching" is defined as "equal after stripping RelabelTypes". * This is used for identifying sort expressions, and we need to allow * binary-compatible relabeling for some cases involving binary-compatible * sort operators. * * Child EC members are ignored unless they belong to given 'relids'. */ EquivalenceMember * find_ec_member_matching_expr(EquivalenceClass *ec, Expr *expr, Relids relids) { ListCell *lc; /* We ignore binary-compatible relabeling on both ends */ while (expr && IsA(expr, RelabelType)) expr = ((RelabelType *) expr)->arg; foreach(lc, ec->ec_members) { EquivalenceMember *em = (EquivalenceMember *) lfirst(lc); Expr *emexpr; /* * We shouldn't be trying to sort by an equivalence class that * contains a constant, so no need to consider such cases any further. */ if (em->em_is_const) continue; /* * Ignore child members unless they belong to the requested rel. */ if (em->em_is_child && !bms_is_subset(em->em_relids, relids)) continue; /* * Match if same expression (after stripping relabel). */ emexpr = em->em_expr; while (emexpr && IsA(emexpr, RelabelType)) emexpr = ((RelabelType *) emexpr)->arg; if (equal(emexpr, expr)) return em; } return NULL; } /* * find_computable_ec_member * Locate an EquivalenceClass member that can be computed from the * expressions appearing in "exprs"; return NULL if no match. * * "exprs" can be either a list of bare expression trees, or a list of * TargetEntry nodes. Either way, it should contain Vars and possibly * Aggrefs and WindowFuncs, which are matched to the corresponding elements * of the EquivalenceClass's expressions. * * Unlike find_ec_member_matching_expr, there's no special provision here * for binary-compatible relabeling. This is intentional: if we have to * compute an expression in this way, setrefs.c is going to insist on exact * matches of Vars to the source tlist. * * Child EC members are ignored unless they belong to given 'relids'. * Also, non-parallel-safe expressions are ignored if 'require_parallel_safe'. * * Note: some callers pass root == NULL for notational reasons. This is OK * when require_parallel_safe is false. */ EquivalenceMember * find_computable_ec_member(PlannerInfo *root, EquivalenceClass *ec, List *exprs, Relids relids, bool require_parallel_safe) { ListCell *lc; foreach(lc, ec->ec_members) { EquivalenceMember *em = (EquivalenceMember *) lfirst(lc); List *exprvars; ListCell *lc2; /* * We shouldn't be trying to sort by an equivalence class that * contains a constant, so no need to consider such cases any further. */ if (em->em_is_const) continue; /* * Ignore child members unless they belong to the requested rel. */ if (em->em_is_child && !bms_is_subset(em->em_relids, relids)) continue; /* * Match if all Vars and quasi-Vars are available in "exprs". */ exprvars = pull_var_clause((Node *) em->em_expr, PVC_INCLUDE_AGGREGATES | PVC_INCLUDE_WINDOWFUNCS | PVC_INCLUDE_PLACEHOLDERS); foreach(lc2, exprvars) { if (!is_exprlist_member(lfirst(lc2), exprs)) break; } list_free(exprvars); if (lc2) continue; /* we hit a non-available Var */ /* * If requested, reject expressions that are not parallel-safe. We * check this last because it's a rather expensive test. */ if (require_parallel_safe && !is_parallel_safe(root, (Node *) em->em_expr)) continue; return em; /* found usable expression */ } return NULL; } /* * is_exprlist_member * Subroutine for find_computable_ec_member: is "node" in "exprs"? * * Per the requirements of that function, "exprs" might or might not have * TargetEntry superstructure. */ static bool is_exprlist_member(Expr *node, List *exprs) { ListCell *lc; foreach(lc, exprs) { Expr *expr = (Expr *) lfirst(lc); if (expr && IsA(expr, TargetEntry)) expr = ((TargetEntry *) expr)->expr; if (equal(node, expr)) return true; } return false; } /* * Find an equivalence class member expression, all of whose Vars, come from * the indicated relation. */ Expr * find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel) { ListCell *lc_em; foreach(lc_em, ec->ec_members) { EquivalenceMember *em = lfirst(lc_em); if (bms_is_subset(em->em_relids, rel->relids) && !bms_is_empty(em->em_relids)) { /* * If there is more than one equivalence member whose Vars are * taken entirely from this relation, we'll be content to choose * any one of those. */ return em->em_expr; } } /* We didn't find any suitable equivalence class expression */ return NULL; } /* * relation_can_be_sorted_early * Can this relation be sorted on this EC before the final output step? * * To succeed, we must find an EC member that prepare_sort_from_pathkeys knows * how to sort on, given the rel's reltarget as input. There are also a few * additional constraints based on the fact that the desired sort will be done * "early", within the scan/join part of the plan. Also, non-parallel-safe * expressions are ignored if 'require_parallel_safe'. * * At some point we might want to return the identified EquivalenceMember, * but for now, callers only want to know if there is one. */ bool relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel, EquivalenceClass *ec, bool require_parallel_safe) { PathTarget *target = rel->reltarget; EquivalenceMember *em; ListCell *lc; /* * Reject volatile ECs immediately; such sorts must always be postponed. */ if (ec->ec_has_volatile) return false; /* * Try to find an EM directly matching some reltarget member. */ foreach(lc, target->exprs) { Expr *targetexpr = (Expr *) lfirst(lc); em = find_ec_member_matching_expr(ec, targetexpr, rel->relids); if (!em) continue; /* * Reject expressions involving set-returning functions, as those * can't be computed early either. (Note: this test and the following * one are effectively checking properties of targetexpr, so there's * no point in asking whether some other EC member would be better.) */ if (expression_returns_set((Node *) em->em_expr)) continue; /* * If requested, reject expressions that are not parallel-safe. We * check this last because it's a rather expensive test. */ if (require_parallel_safe && !is_parallel_safe(root, (Node *) em->em_expr)) continue; return true; } /* * Try to find a expression computable from the reltarget. */ em = find_computable_ec_member(root, ec, target->exprs, rel->relids, require_parallel_safe); if (!em) return false; /* * Reject expressions involving set-returning functions, as those can't be * computed early either. (There's no point in looking for another EC * member in this case; since SRFs can't appear in WHERE, they cannot * belong to multi-member ECs.) */ if (expression_returns_set((Node *) em->em_expr)) return false; return true; } /* * generate_base_implied_equalities * Generate any restriction clauses that we can deduce from equivalence * classes. * * When an EC contains pseudoconstants, our strategy is to generate * "member = const1" clauses where const1 is the first constant member, for * every other member (including other constants). If we are able to do this * then we don't need any "var = var" comparisons because we've successfully * constrained all the vars at their points of creation. If we fail to * generate any of these clauses due to lack of cross-type operators, we fall * back to the "ec_broken" strategy described below. (XXX if there are * multiple constants of different types, it's possible that we might succeed * in forming all the required clauses if we started from a different const * member; but this seems a sufficiently hokey corner case to not be worth * spending lots of cycles on.) * * For ECs that contain no pseudoconstants, we generate derived clauses * "member1 = member2" for each pair of members belonging to the same base * relation (actually, if there are more than two for the same base relation, * we only need enough clauses to link each to each other). This provides * the base case for the recursion: each row emitted by a base relation scan * will constrain all computable members of the EC to be equal. As each * join path is formed, we'll add additional derived clauses on-the-fly * to maintain this invariant (see generate_join_implied_equalities). * * If the opfamilies used by the EC do not provide complete sets of cross-type * equality operators, it is possible that we will fail to generate a clause * that must be generated to maintain the invariant. (An example: given * "WHERE a.x = b.y AND b.y = a.z", the scheme breaks down if we cannot * generate "a.x = a.z" as a restriction clause for A.) In this case we mark * the EC "ec_broken" and fall back to regurgitating its original source * RestrictInfos at appropriate times. We do not try to retract any derived * clauses already generated from the broken EC, so the resulting plan could * be poor due to bad selectivity estimates caused by redundant clauses. But * the correct solution to that is to fix the opfamilies ... * * Equality clauses derived by this function are passed off to * process_implied_equality (in plan/initsplan.c) to be inserted into the * restrictinfo datastructures. Note that this must be called after initial * scanning of the quals and before Path construction begins. * * We make no attempt to avoid generating duplicate RestrictInfos here: we * don't search ec_sources or ec_derives for matches. It doesn't really * seem worth the trouble to do so. */ void generate_base_implied_equalities(PlannerInfo *root) { int ec_index; ListCell *lc; /* * At this point, we're done absorbing knowledge of equivalences in the * query, so no further EC merging should happen, and ECs remaining in the * eq_classes list can be considered canonical. (But note that it's still * possible for new single-member ECs to be added through * get_eclass_for_sort_expr().) */ root->ec_merging_done = true; ec_index = 0; foreach(lc, root->eq_classes) { EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc); bool can_generate_joinclause = false; int i; Assert(ec->ec_merged == NULL); /* else shouldn't be in list */ Assert(!ec->ec_broken); /* not yet anyway... */ /* * Generate implied equalities that are restriction clauses. * Single-member ECs won't generate any deductions, either here or at * the join level. */ if (list_length(ec->ec_members) > 1) { if (ec->ec_has_const) generate_base_implied_equalities_const(root, ec); else generate_base_implied_equalities_no_const(root, ec); /* Recover if we failed to generate required derived clauses */ if (ec->ec_broken) generate_base_implied_equalities_broken(root, ec); /* Detect whether this EC might generate join clauses */ can_generate_joinclause = (bms_membership(ec->ec_relids) == BMS_MULTIPLE); } /* * Mark the base rels cited in each eclass (which should all exist by * now) with the eq_classes indexes of all eclasses mentioning them. * This will let us avoid searching in subsequent lookups. While * we're at it, we can mark base rels that have pending eclass joins; * this is a cheap version of has_relevant_eclass_joinclause(). */ i = -1; while ((i = bms_next_member(ec->ec_relids, i)) > 0) { RelOptInfo *rel = root->simple_rel_array[i]; Assert(rel->reloptkind == RELOPT_BASEREL); rel->eclass_indexes = bms_add_member(rel->eclass_indexes, ec_index); if (can_generate_joinclause) rel->has_eclass_joins = true; } ec_index++; } } /* * generate_base_implied_equalities when EC contains pseudoconstant(s) */ static void generate_base_implied_equalities_const(PlannerInfo *root, EquivalenceClass *ec) { EquivalenceMember *const_em = NULL; ListCell *lc; /* * In the trivial case where we just had one "var = const" clause, push * the original clause back into the main planner machinery. There is * nothing to be gained by doing it differently, and we save the effort to * re-build and re-analyze an equality clause that will be exactly * equivalent to the old one. */ if (list_length(ec->ec_members) == 2 && list_length(ec->ec_sources) == 1) { RestrictInfo *restrictinfo = (RestrictInfo *) linitial(ec->ec_sources); if (bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE) { distribute_restrictinfo_to_rels(root, restrictinfo); return; } } /* * Find the constant member to use. We prefer an actual constant to * pseudo-constants (such as Params), because the constraint exclusion * machinery might be able to exclude relations on the basis of generated * "var = const" equalities, but "var = param" won't work for that. */ foreach(lc, ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc); if (cur_em->em_is_const) { const_em = cur_em; if (IsA(cur_em->em_expr, Const)) break; } } Assert(const_em != NULL); /* Generate a derived equality against each other member */ foreach(lc, ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc); Oid eq_op; RestrictInfo *rinfo; Assert(!cur_em->em_is_child); /* no children yet */ if (cur_em == const_em) continue; eq_op = select_equality_operator(ec, cur_em->em_datatype, const_em->em_datatype); if (!OidIsValid(eq_op)) { /* failed... */ ec->ec_broken = true; break; } rinfo = process_implied_equality(root, eq_op, ec->ec_collation, cur_em->em_expr, const_em->em_expr, bms_copy(ec->ec_relids), bms_union(cur_em->em_nullable_relids, const_em->em_nullable_relids), ec->ec_min_security, ec->ec_below_outer_join, cur_em->em_is_const); /* * If the clause didn't degenerate to a constant, fill in the correct * markings for a mergejoinable clause, and save it in ec_derives. (We * will not re-use such clauses directly, but selectivity estimation * may consult the list later. Note that this use of ec_derives does * not overlap with its use for join clauses, since we never generate * join clauses from an ec_has_const eclass.) */ if (rinfo && rinfo->mergeopfamilies) { /* it's not redundant, so don't set parent_ec */ rinfo->left_ec = rinfo->right_ec = ec; rinfo->left_em = cur_em; rinfo->right_em = const_em; ec->ec_derives = lappend(ec->ec_derives, rinfo); } } } /* * generate_base_implied_equalities when EC contains no pseudoconstants */ static void generate_base_implied_equalities_no_const(PlannerInfo *root, EquivalenceClass *ec) { EquivalenceMember **prev_ems; ListCell *lc; /* * We scan the EC members once and track the last-seen member for each * base relation. When we see another member of the same base relation, * we generate "prev_em = cur_em". This results in the minimum number of * derived clauses, but it's possible that it will fail when a different * ordering would succeed. XXX FIXME: use a UNION-FIND algorithm similar * to the way we build merged ECs. (Use a list-of-lists for each rel.) */ prev_ems = (EquivalenceMember **) palloc0(root->simple_rel_array_size * sizeof(EquivalenceMember *)); foreach(lc, ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc); int relid; Assert(!cur_em->em_is_child); /* no children yet */ if (!bms_get_singleton_member(cur_em->em_relids, &relid)) continue; Assert(relid < root->simple_rel_array_size); if (prev_ems[relid] != NULL) { EquivalenceMember *prev_em = prev_ems[relid]; Oid eq_op; RestrictInfo *rinfo; eq_op = select_equality_operator(ec, prev_em->em_datatype, cur_em->em_datatype); if (!OidIsValid(eq_op)) { /* failed... */ ec->ec_broken = true; break; } rinfo = process_implied_equality(root, eq_op, ec->ec_collation, prev_em->em_expr, cur_em->em_expr, bms_copy(ec->ec_relids), bms_union(prev_em->em_nullable_relids, cur_em->em_nullable_relids), ec->ec_min_security, ec->ec_below_outer_join, false); /* * If the clause didn't degenerate to a constant, fill in the * correct markings for a mergejoinable clause. We don't put it * in ec_derives however; we don't currently need to re-find such * clauses, and we don't want to clutter that list with non-join * clauses. */ if (rinfo && rinfo->mergeopfamilies) { /* it's not redundant, so don't set parent_ec */ rinfo->left_ec = rinfo->right_ec = ec; rinfo->left_em = prev_em; rinfo->right_em = cur_em; } } prev_ems[relid] = cur_em; } pfree(prev_ems); /* * We also have to make sure that all the Vars used in the member clauses * will be available at any join node we might try to reference them at. * For the moment we force all the Vars to be available at all join nodes * for this eclass. Perhaps this could be improved by doing some * pre-analysis of which members we prefer to join, but it's no worse than * what happened in the pre-8.3 code. */ foreach(lc, ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc); List *vars = pull_var_clause((Node *) cur_em->em_expr, PVC_RECURSE_AGGREGATES | PVC_RECURSE_WINDOWFUNCS | PVC_INCLUDE_PLACEHOLDERS); add_vars_to_targetlist(root, vars, ec->ec_relids, false); list_free(vars); } } /* * generate_base_implied_equalities cleanup after failure * * What we must do here is push any zero- or one-relation source RestrictInfos * of the EC back into the main restrictinfo datastructures. Multi-relation * clauses will be regurgitated later by generate_join_implied_equalities(). * (We do it this way to maintain continuity with the case that ec_broken * becomes set only after we've gone up a join level or two.) However, for * an EC that contains constants, we can adopt a simpler strategy and just * throw back all the source RestrictInfos immediately; that works because * we know that such an EC can't become broken later. (This rule justifies * ignoring ec_has_const ECs in generate_join_implied_equalities, even when * they are broken.) */ static void generate_base_implied_equalities_broken(PlannerInfo *root, EquivalenceClass *ec) { ListCell *lc; foreach(lc, ec->ec_sources) { RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc); if (ec->ec_has_const || bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE) distribute_restrictinfo_to_rels(root, restrictinfo); } } /* * generate_join_implied_equalities * Generate any join clauses that we can deduce from equivalence classes. * * At a join node, we must enforce restriction clauses sufficient to ensure * that all equivalence-class members computable at that node are equal. * Since the set of clauses to enforce can vary depending on which subset * relations are the inputs, we have to compute this afresh for each join * relation pair. Hence a fresh List of RestrictInfo nodes is built and * passed back on each call. * * In addition to its use at join nodes, this can be applied to generate * eclass-based join clauses for use in a parameterized scan of a base rel. * The reason for the asymmetry of specifying the inner rel as a RelOptInfo * and the outer rel by Relids is that this usage occurs before we have * built any join RelOptInfos. * * An annoying special case for parameterized scans is that the inner rel can * be an appendrel child (an "other rel"). In this case we must generate * appropriate clauses using child EC members. add_child_rel_equivalences * must already have been done for the child rel. * * The results are sufficient for use in merge, hash, and plain nestloop join * methods. We do not worry here about selecting clauses that are optimal * for use in a parameterized indexscan. indxpath.c makes its own selections * of clauses to use, and if the ones we pick here are redundant with those, * the extras will be eliminated at createplan time, using the parent_ec * markers that we provide (see is_redundant_derived_clause()). * * Because the same join clauses are likely to be needed multiple times as * we consider different join paths, we avoid generating multiple copies: * whenever we select a particular pair of EquivalenceMembers to join, * we check to see if the pair matches any original clause (in ec_sources) * or previously-built clause (in ec_derives). This saves memory and allows * re-use of information cached in RestrictInfos. * * join_relids should always equal bms_union(outer_relids, inner_rel->relids). * We could simplify this function's API by computing it internally, but in * most current uses, the caller has the value at hand anyway. */ List * generate_join_implied_equalities(PlannerInfo *root, Relids join_relids, Relids outer_relids, RelOptInfo *inner_rel) { List *result = NIL; Relids inner_relids = inner_rel->relids; Relids nominal_inner_relids; Relids nominal_join_relids; Bitmapset *matching_ecs; int i; /* If inner rel is a child, extra setup work is needed */ if (IS_OTHER_REL(inner_rel)) { Assert(!bms_is_empty(inner_rel->top_parent_relids)); /* Fetch relid set for the topmost parent rel */ nominal_inner_relids = inner_rel->top_parent_relids; /* ECs will be marked with the parent's relid, not the child's */ nominal_join_relids = bms_union(outer_relids, nominal_inner_relids); } else { nominal_inner_relids = inner_relids; nominal_join_relids = join_relids; } /* * Get all eclasses that mention both inner and outer sides of the join */ matching_ecs = get_common_eclass_indexes(root, nominal_inner_relids, outer_relids); i = -1; while ((i = bms_next_member(matching_ecs, i)) >= 0) { EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i); List *sublist = NIL; /* ECs containing consts do not need any further enforcement */ if (ec->ec_has_const) continue; /* Single-member ECs won't generate any deductions */ if (list_length(ec->ec_members) <= 1) continue; /* Sanity check that this eclass overlaps the join */ Assert(bms_overlap(ec->ec_relids, nominal_join_relids)); if (!ec->ec_broken) sublist = generate_join_implied_equalities_normal(root, ec, join_relids, outer_relids, inner_relids); /* Recover if we failed to generate required derived clauses */ if (ec->ec_broken) sublist = generate_join_implied_equalities_broken(root, ec, nominal_join_relids, outer_relids, nominal_inner_relids, inner_rel); result = list_concat(result, sublist); } return result; } /* * generate_join_implied_equalities_for_ecs * As above, but consider only the listed ECs. */ List * generate_join_implied_equalities_for_ecs(PlannerInfo *root, List *eclasses, Relids join_relids, Relids outer_relids, RelOptInfo *inner_rel) { List *result = NIL; Relids inner_relids = inner_rel->relids; Relids nominal_inner_relids; Relids nominal_join_relids; ListCell *lc; /* If inner rel is a child, extra setup work is needed */ if (IS_OTHER_REL(inner_rel)) { Assert(!bms_is_empty(inner_rel->top_parent_relids)); /* Fetch relid set for the topmost parent rel */ nominal_inner_relids = inner_rel->top_parent_relids; /* ECs will be marked with the parent's relid, not the child's */ nominal_join_relids = bms_union(outer_relids, nominal_inner_relids); } else { nominal_inner_relids = inner_relids; nominal_join_relids = join_relids; } foreach(lc, eclasses) { EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc); List *sublist = NIL; /* ECs containing consts do not need any further enforcement */ if (ec->ec_has_const) continue; /* Single-member ECs won't generate any deductions */ if (list_length(ec->ec_members) <= 1) continue; /* We can quickly ignore any that don't overlap the join, too */ if (!bms_overlap(ec->ec_relids, nominal_join_relids)) continue; if (!ec->ec_broken) sublist = generate_join_implied_equalities_normal(root, ec, join_relids, outer_relids, inner_relids); /* Recover if we failed to generate required derived clauses */ if (ec->ec_broken) sublist = generate_join_implied_equalities_broken(root, ec, nominal_join_relids, outer_relids, nominal_inner_relids, inner_rel); result = list_concat(result, sublist); } return result; } /* * generate_join_implied_equalities for a still-valid EC */ static List * generate_join_implied_equalities_normal(PlannerInfo *root, EquivalenceClass *ec, Relids join_relids, Relids outer_relids, Relids inner_relids) { List *result = NIL; List *new_members = NIL; List *outer_members = NIL; List *inner_members = NIL; ListCell *lc1; /* * First, scan the EC to identify member values that are computable at the * outer rel, at the inner rel, or at this relation but not in either * input rel. The outer-rel members should already be enforced equal, * likewise for the inner-rel members. We'll need to create clauses to * enforce that any newly computable members are all equal to each other * as well as to at least one input member, plus enforce at least one * outer-rel member equal to at least one inner-rel member. */ foreach(lc1, ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1); /* * We don't need to check explicitly for child EC members. This test * against join_relids will cause them to be ignored except when * considering a child inner rel, which is what we want. */ if (!bms_is_subset(cur_em->em_relids, join_relids)) continue; /* not computable yet, or wrong child */ if (bms_is_subset(cur_em->em_relids, outer_relids)) outer_members = lappend(outer_members, cur_em); else if (bms_is_subset(cur_em->em_relids, inner_relids)) inner_members = lappend(inner_members, cur_em); else new_members = lappend(new_members, cur_em); } /* * First, select the joinclause if needed. We can equate any one outer * member to any one inner member, but we have to find a datatype * combination for which an opfamily member operator exists. If we have * choices, we prefer simple Var members (possibly with RelabelType) since * these are (a) cheapest to compute at runtime and (b) most likely to * have useful statistics. Also, prefer operators that are also * hashjoinable. */ if (outer_members && inner_members) { EquivalenceMember *best_outer_em = NULL; EquivalenceMember *best_inner_em = NULL; Oid best_eq_op = InvalidOid; int best_score = -1; RestrictInfo *rinfo; foreach(lc1, outer_members) { EquivalenceMember *outer_em = (EquivalenceMember *) lfirst(lc1); ListCell *lc2; foreach(lc2, inner_members) { EquivalenceMember *inner_em = (EquivalenceMember *) lfirst(lc2); Oid eq_op; int score; eq_op = select_equality_operator(ec, outer_em->em_datatype, inner_em->em_datatype); if (!OidIsValid(eq_op)) continue; score = 0; if (IsA(outer_em->em_expr, Var) || (IsA(outer_em->em_expr, RelabelType) && IsA(((RelabelType *) outer_em->em_expr)->arg, Var))) score++; if (IsA(inner_em->em_expr, Var) || (IsA(inner_em->em_expr, RelabelType) && IsA(((RelabelType *) inner_em->em_expr)->arg, Var))) score++; if (op_hashjoinable(eq_op, exprType((Node *) outer_em->em_expr))) score++; if (score > best_score) { best_outer_em = outer_em; best_inner_em = inner_em; best_eq_op = eq_op; best_score = score; if (best_score == 3) break; /* no need to look further */ } } if (best_score == 3) break; /* no need to look further */ } if (best_score < 0) { /* failed... */ ec->ec_broken = true; return NIL; } /* * Create clause, setting parent_ec to mark it as redundant with other * joinclauses */ rinfo = create_join_clause(root, ec, best_eq_op, best_outer_em, best_inner_em, ec); result = lappend(result, rinfo); } /* * Now deal with building restrictions for any expressions that involve * Vars from both sides of the join. We have to equate all of these to * each other as well as to at least one old member (if any). * * XXX as in generate_base_implied_equalities_no_const, we could be a lot * smarter here to avoid unnecessary failures in cross-type situations. * For now, use the same left-to-right method used there. */ if (new_members) { List *old_members = list_concat(outer_members, inner_members); EquivalenceMember *prev_em = NULL; RestrictInfo *rinfo; /* For now, arbitrarily take the first old_member as the one to use */ if (old_members) new_members = lappend(new_members, linitial(old_members)); foreach(lc1, new_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1); if (prev_em != NULL) { Oid eq_op; eq_op = select_equality_operator(ec, prev_em->em_datatype, cur_em->em_datatype); if (!OidIsValid(eq_op)) { /* failed... */ ec->ec_broken = true; return NIL; } /* do NOT set parent_ec, this qual is not redundant! */ rinfo = create_join_clause(root, ec, eq_op, prev_em, cur_em, NULL); result = lappend(result, rinfo); } prev_em = cur_em; } } return result; } /* * generate_join_implied_equalities cleanup after failure * * Return any original RestrictInfos that are enforceable at this join. * * In the case of a child inner relation, we have to translate the * original RestrictInfos from parent to child Vars. */ static List * generate_join_implied_equalities_broken(PlannerInfo *root, EquivalenceClass *ec, Relids nominal_join_relids, Relids outer_relids, Relids nominal_inner_relids, RelOptInfo *inner_rel) { List *result = NIL; ListCell *lc; foreach(lc, ec->ec_sources) { RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc); Relids clause_relids = restrictinfo->required_relids; if (bms_is_subset(clause_relids, nominal_join_relids) && !bms_is_subset(clause_relids, outer_relids) && !bms_is_subset(clause_relids, nominal_inner_relids)) result = lappend(result, restrictinfo); } /* * If we have to translate, just brute-force apply adjust_appendrel_attrs * to all the RestrictInfos at once. This will result in returning * RestrictInfos that are not listed in ec_derives, but there shouldn't be * any duplication, and it's a sufficiently narrow corner case that we * shouldn't sweat too much over it anyway. * * Since inner_rel might be an indirect descendant of the baserel * mentioned in the ec_sources clauses, we have to be prepared to apply * multiple levels of Var translation. */ if (IS_OTHER_REL(inner_rel) && result != NIL) result = (List *) adjust_appendrel_attrs_multilevel(root, (Node *) result, inner_rel->relids, inner_rel->top_parent_relids); return result; } /* * select_equality_operator * Select a suitable equality operator for comparing two EC members * * Returns InvalidOid if no operator can be found for this datatype combination */ static Oid select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype) { ListCell *lc; foreach(lc, ec->ec_opfamilies) { Oid opfamily = lfirst_oid(lc); Oid opno; opno = get_opfamily_member(opfamily, lefttype, righttype, BTEqualStrategyNumber); if (!OidIsValid(opno)) continue; /* If no barrier quals in query, don't worry about leaky operators */ if (ec->ec_max_security == 0) return opno; /* Otherwise, insist that selected operators be leakproof */ if (get_func_leakproof(get_opcode(opno))) return opno; } return InvalidOid; } /* * create_join_clause * Find or make a RestrictInfo comparing the two given EC members * with the given operator. * * parent_ec is either equal to ec (if the clause is a potentially-redundant * join clause) or NULL (if not). We have to treat this as part of the * match requirements --- it's possible that a clause comparing the same two * EMs is a join clause in one join path and a restriction clause in another. */ static RestrictInfo * create_join_clause(PlannerInfo *root, EquivalenceClass *ec, Oid opno, EquivalenceMember *leftem, EquivalenceMember *rightem, EquivalenceClass *parent_ec) { RestrictInfo *rinfo; ListCell *lc; MemoryContext oldcontext; /* * Search to see if we already built a RestrictInfo for this pair of * EquivalenceMembers. We can use either original source clauses or * previously-derived clauses. The check on opno is probably redundant, * but be safe ... */ foreach(lc, ec->ec_sources) { rinfo = (RestrictInfo *) lfirst(lc); if (rinfo->left_em == leftem && rinfo->right_em == rightem && rinfo->parent_ec == parent_ec && opno == ((OpExpr *) rinfo->clause)->opno) return rinfo; } foreach(lc, ec->ec_derives) { rinfo = (RestrictInfo *) lfirst(lc); if (rinfo->left_em == leftem && rinfo->right_em == rightem && rinfo->parent_ec == parent_ec && opno == ((OpExpr *) rinfo->clause)->opno) return rinfo; } /* * Not there, so build it, in planner context so we can re-use it. (Not * important in normal planning, but definitely so in GEQO.) */ oldcontext = MemoryContextSwitchTo(root->planner_cxt); rinfo = build_implied_join_equality(root, opno, ec->ec_collation, leftem->em_expr, rightem->em_expr, bms_union(leftem->em_relids, rightem->em_relids), bms_union(leftem->em_nullable_relids, rightem->em_nullable_relids), ec->ec_min_security); /* Mark the clause as redundant, or not */ rinfo->parent_ec = parent_ec; /* * We know the correct values for left_ec/right_ec, ie this particular EC, * so we can just set them directly instead of forcing another lookup. */ rinfo->left_ec = ec; rinfo->right_ec = ec; /* Mark it as usable with these EMs */ rinfo->left_em = leftem; rinfo->right_em = rightem; /* and save it for possible re-use */ ec->ec_derives = lappend(ec->ec_derives, rinfo); MemoryContextSwitchTo(oldcontext); return rinfo; } /* * reconsider_outer_join_clauses * Re-examine any outer-join clauses that were set aside by * distribute_qual_to_rels(), and see if we can derive any * EquivalenceClasses from them. Then, if they were not made * redundant, push them out into the regular join-clause lists. * * When we have mergejoinable clauses A = B that are outer-join clauses, * we can't blindly combine them with other clauses A = C to deduce B = C, * since in fact the "equality" A = B won't necessarily hold above the * outer join (one of the variables might be NULL instead). Nonetheless * there are cases where we can add qual clauses using transitivity. * * One case that we look for here is an outer-join clause OUTERVAR = INNERVAR * for which there is also an equivalence clause OUTERVAR = CONSTANT. * It is safe and useful to push a clause INNERVAR = CONSTANT into the * evaluation of the inner (nullable) relation, because any inner rows not * meeting this condition will not contribute to the outer-join result anyway. * (Any outer rows they could join to will be eliminated by the pushed-down * equivalence clause.) * * Note that the above rule does not work for full outer joins; nor is it * very interesting to consider cases where the generated equivalence clause * would involve relations outside the outer join, since such clauses couldn't * be pushed into the inner side's scan anyway. So the restriction to * outervar = pseudoconstant is not really giving up anything. * * For full-join cases, we can only do something useful if it's a FULL JOIN * USING and a merged column has an equivalence MERGEDVAR = CONSTANT. * By the time it gets here, the merged column will look like * COALESCE(LEFTVAR, RIGHTVAR) * and we will have a full-join clause LEFTVAR = RIGHTVAR that we can match * the COALESCE expression to. In this situation we can push LEFTVAR = CONSTANT * and RIGHTVAR = CONSTANT into the input relations, since any rows not * meeting these conditions cannot contribute to the join result. * * Again, there isn't any traction to be gained by trying to deal with * clauses comparing a mergedvar to a non-pseudoconstant. So we can make * use of the EquivalenceClasses to search for matching variables that were * equivalenced to constants. The interesting outer-join clauses were * accumulated for us by distribute_qual_to_rels. * * When we find one of these cases, we implement the changes we want by * generating a new equivalence clause INNERVAR = CONSTANT (or LEFTVAR, etc) * and pushing it into the EquivalenceClass structures. This is because we * may already know that INNERVAR is equivalenced to some other var(s), and * we'd like the constant to propagate to them too. Note that it would be * unsafe to merge any existing EC for INNERVAR with the OUTERVAR's EC --- * that could result in propagating constant restrictions from * INNERVAR to OUTERVAR, which would be very wrong. * * It's possible that the INNERVAR is also an OUTERVAR for some other * outer-join clause, in which case the process can be repeated. So we repeat * looping over the lists of clauses until no further deductions can be made. * Whenever we do make a deduction, we remove the generating clause from the * lists, since we don't want to make the same deduction twice. * * If we don't find any match for a set-aside outer join clause, we must * throw it back into the regular joinclause processing by passing it to * distribute_restrictinfo_to_rels(). If we do generate a derived clause, * however, the outer-join clause is redundant. We still throw it back, * because otherwise the join will be seen as a clauseless join and avoided * during join order searching; but we mark it as redundant to keep from * messing up the joinrel's size estimate. (This behavior means that the * API for this routine is uselessly complex: we could have just put all * the clauses into the regular processing initially. We keep it because * someday we might want to do something else, such as inserting "dummy" * joinclauses instead of real ones.) * * Outer join clauses that are marked outerjoin_delayed are special: this * condition means that one or both VARs might go to null due to a lower * outer join. We can still push a constant through the clause, but only * if its operator is strict; and we *have to* throw the clause back into * regular joinclause processing. By keeping the strict join clause, * we ensure that any null-extended rows that are mistakenly generated due * to suppressing rows not matching the constant will be rejected at the * upper outer join. (This doesn't work for full-join clauses.) */ void reconsider_outer_join_clauses(PlannerInfo *root) { bool found; ListCell *cell; /* Outer loop repeats until we find no more deductions */ do { found = false; /* Process the LEFT JOIN clauses */ foreach(cell, root->left_join_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell); if (reconsider_outer_join_clause(root, rinfo, true)) { found = true; /* remove it from the list */ root->left_join_clauses = foreach_delete_current(root->left_join_clauses, cell); /* we throw it back anyway (see notes above) */ /* but the thrown-back clause has no extra selectivity */ rinfo->norm_selec = 2.0; rinfo->outer_selec = 1.0; distribute_restrictinfo_to_rels(root, rinfo); } } /* Process the RIGHT JOIN clauses */ foreach(cell, root->right_join_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell); if (reconsider_outer_join_clause(root, rinfo, false)) { found = true; /* remove it from the list */ root->right_join_clauses = foreach_delete_current(root->right_join_clauses, cell); /* we throw it back anyway (see notes above) */ /* but the thrown-back clause has no extra selectivity */ rinfo->norm_selec = 2.0; rinfo->outer_selec = 1.0; distribute_restrictinfo_to_rels(root, rinfo); } } /* Process the FULL JOIN clauses */ foreach(cell, root->full_join_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell); if (reconsider_full_join_clause(root, rinfo)) { found = true; /* remove it from the list */ root->full_join_clauses = foreach_delete_current(root->full_join_clauses, cell); /* we throw it back anyway (see notes above) */ /* but the thrown-back clause has no extra selectivity */ rinfo->norm_selec = 2.0; rinfo->outer_selec = 1.0; distribute_restrictinfo_to_rels(root, rinfo); } } } while (found); /* Now, any remaining clauses have to be thrown back */ foreach(cell, root->left_join_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell); distribute_restrictinfo_to_rels(root, rinfo); } foreach(cell, root->right_join_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell); distribute_restrictinfo_to_rels(root, rinfo); } foreach(cell, root->full_join_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell); distribute_restrictinfo_to_rels(root, rinfo); } } /* * reconsider_outer_join_clauses for a single LEFT/RIGHT JOIN clause * * Returns true if we were able to propagate a constant through the clause. */ static bool reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo, bool outer_on_left) { Expr *outervar, *innervar; Oid opno, collation, left_type, right_type, inner_datatype; Relids inner_relids, inner_nullable_relids; ListCell *lc1; Assert(is_opclause(rinfo->clause)); opno = ((OpExpr *) rinfo->clause)->opno; collation = ((OpExpr *) rinfo->clause)->inputcollid; /* If clause is outerjoin_delayed, operator must be strict */ if (rinfo->outerjoin_delayed && !op_strict(opno)) return false; /* Extract needed info from the clause */ op_input_types(opno, &left_type, &right_type); if (outer_on_left) { outervar = (Expr *) get_leftop(rinfo->clause); innervar = (Expr *) get_rightop(rinfo->clause); inner_datatype = right_type; inner_relids = rinfo->right_relids; } else { outervar = (Expr *) get_rightop(rinfo->clause); innervar = (Expr *) get_leftop(rinfo->clause); inner_datatype = left_type; inner_relids = rinfo->left_relids; } inner_nullable_relids = bms_intersect(inner_relids, rinfo->nullable_relids); /* Scan EquivalenceClasses for a match to outervar */ foreach(lc1, root->eq_classes) { EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1); bool match; ListCell *lc2; /* Ignore EC unless it contains pseudoconstants */ if (!cur_ec->ec_has_const) continue; /* Never match to a volatile EC */ if (cur_ec->ec_has_volatile) continue; /* It has to match the outer-join clause as to semantics, too */ if (collation != cur_ec->ec_collation) continue; if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies)) continue; /* Does it contain a match to outervar? */ match = false; foreach(lc2, cur_ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2); Assert(!cur_em->em_is_child); /* no children yet */ if (equal(outervar, cur_em->em_expr)) { match = true; break; } } if (!match) continue; /* no match, so ignore this EC */ /* * Yes it does! Try to generate a clause INNERVAR = CONSTANT for each * CONSTANT in the EC. Note that we must succeed with at least one * constant before we can decide to throw away the outer-join clause. */ match = false; foreach(lc2, cur_ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2); Oid eq_op; RestrictInfo *newrinfo; if (!cur_em->em_is_const) continue; /* ignore non-const members */ eq_op = select_equality_operator(cur_ec, inner_datatype, cur_em->em_datatype); if (!OidIsValid(eq_op)) continue; /* can't generate equality */ newrinfo = build_implied_join_equality(root, eq_op, cur_ec->ec_collation, innervar, cur_em->em_expr, bms_copy(inner_relids), bms_copy(inner_nullable_relids), cur_ec->ec_min_security); if (process_equivalence(root, &newrinfo, true)) match = true; } /* * If we were able to equate INNERVAR to any constant, report success. * Otherwise, fall out of the search loop, since we know the OUTERVAR * appears in at most one EC. */ if (match) return true; else break; } return false; /* failed to make any deduction */ } /* * reconsider_outer_join_clauses for a single FULL JOIN clause * * Returns true if we were able to propagate a constant through the clause. */ static bool reconsider_full_join_clause(PlannerInfo *root, RestrictInfo *rinfo) { Expr *leftvar; Expr *rightvar; Oid opno, collation, left_type, right_type; Relids left_relids, right_relids, left_nullable_relids, right_nullable_relids; ListCell *lc1; /* Can't use an outerjoin_delayed clause here */ if (rinfo->outerjoin_delayed) return false; /* Extract needed info from the clause */ Assert(is_opclause(rinfo->clause)); opno = ((OpExpr *) rinfo->clause)->opno; collation = ((OpExpr *) rinfo->clause)->inputcollid; op_input_types(opno, &left_type, &right_type); leftvar = (Expr *) get_leftop(rinfo->clause); rightvar = (Expr *) get_rightop(rinfo->clause); left_relids = rinfo->left_relids; right_relids = rinfo->right_relids; left_nullable_relids = bms_intersect(left_relids, rinfo->nullable_relids); right_nullable_relids = bms_intersect(right_relids, rinfo->nullable_relids); foreach(lc1, root->eq_classes) { EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1); EquivalenceMember *coal_em = NULL; bool match; bool matchleft; bool matchright; ListCell *lc2; int coal_idx = -1; /* Ignore EC unless it contains pseudoconstants */ if (!cur_ec->ec_has_const) continue; /* Never match to a volatile EC */ if (cur_ec->ec_has_volatile) continue; /* It has to match the outer-join clause as to semantics, too */ if (collation != cur_ec->ec_collation) continue; if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies)) continue; /* * Does it contain a COALESCE(leftvar, rightvar) construct? * * We can assume the COALESCE() inputs are in the same order as the * join clause, since both were automatically generated in the cases * we care about. * * XXX currently this may fail to match in cross-type cases because * the COALESCE will contain typecast operations while the join clause * may not (if there is a cross-type mergejoin operator available for * the two column types). Is it OK to strip implicit coercions from * the COALESCE arguments? */ match = false; foreach(lc2, cur_ec->ec_members) { coal_em = (EquivalenceMember *) lfirst(lc2); Assert(!coal_em->em_is_child); /* no children yet */ if (IsA(coal_em->em_expr, CoalesceExpr)) { CoalesceExpr *cexpr = (CoalesceExpr *) coal_em->em_expr; Node *cfirst; Node *csecond; if (list_length(cexpr->args) != 2) continue; cfirst = (Node *) linitial(cexpr->args); csecond = (Node *) lsecond(cexpr->args); if (equal(leftvar, cfirst) && equal(rightvar, csecond)) { coal_idx = foreach_current_index(lc2); match = true; break; } } } if (!match) continue; /* no match, so ignore this EC */ /* * Yes it does! Try to generate clauses LEFTVAR = CONSTANT and * RIGHTVAR = CONSTANT for each CONSTANT in the EC. Note that we must * succeed with at least one constant for each var before we can * decide to throw away the outer-join clause. */ matchleft = matchright = false; foreach(lc2, cur_ec->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2); Oid eq_op; RestrictInfo *newrinfo; if (!cur_em->em_is_const) continue; /* ignore non-const members */ eq_op = select_equality_operator(cur_ec, left_type, cur_em->em_datatype); if (OidIsValid(eq_op)) { newrinfo = build_implied_join_equality(root, eq_op, cur_ec->ec_collation, leftvar, cur_em->em_expr, bms_copy(left_relids), bms_copy(left_nullable_relids), cur_ec->ec_min_security); if (process_equivalence(root, &newrinfo, true)) matchleft = true; } eq_op = select_equality_operator(cur_ec, right_type, cur_em->em_datatype); if (OidIsValid(eq_op)) { newrinfo = build_implied_join_equality(root, eq_op, cur_ec->ec_collation, rightvar, cur_em->em_expr, bms_copy(right_relids), bms_copy(right_nullable_relids), cur_ec->ec_min_security); if (process_equivalence(root, &newrinfo, true)) matchright = true; } } /* * If we were able to equate both vars to constants, we're done, and * we can throw away the full-join clause as redundant. Moreover, we * can remove the COALESCE entry from the EC, since the added * restrictions ensure it will always have the expected value. (We * don't bother trying to update ec_relids or ec_sources.) */ if (matchleft && matchright) { cur_ec->ec_members = list_delete_nth_cell(cur_ec->ec_members, coal_idx); return true; } /* * Otherwise, fall out of the search loop, since we know the COALESCE * appears in at most one EC (XXX might stop being true if we allow * stripping of coercions above?) */ break; } return false; /* failed to make any deduction */ } /* * exprs_known_equal * Detect whether two expressions are known equal due to equivalence * relationships. * * Actually, this only shows that the expressions are equal according * to some opfamily's notion of equality --- but we only use it for * selectivity estimation, so a fuzzy idea of equality is OK. * * Note: does not bother to check for "equal(item1, item2)"; caller must * check that case if it's possible to pass identical items. */ bool exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2) { ListCell *lc1; foreach(lc1, root->eq_classes) { EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1); bool item1member = false; bool item2member = false; ListCell *lc2; /* Never match to a volatile EC */ if (ec->ec_has_volatile) continue; foreach(lc2, ec->ec_members) { EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2); if (em->em_is_child) continue; /* ignore children here */ if (equal(item1, em->em_expr)) item1member = true; else if (equal(item2, em->em_expr)) item2member = true; /* Exit as soon as equality is proven */ if (item1member && item2member) return true; } } return false; } /* * match_eclasses_to_foreign_key_col * See whether a foreign key column match is proven by any eclass. * * If the referenced and referencing Vars of the fkey's colno'th column are * known equal due to any eclass, return that eclass; otherwise return NULL. * (In principle there might be more than one matching eclass if multiple * collations are involved, but since collation doesn't matter for equality, * we ignore that fine point here.) This is much like exprs_known_equal, * except that we insist on the comparison operator matching the eclass, so * that the result is definite not approximate. * * On success, we also set fkinfo->eclass[colno] to the matching eclass, * and set fkinfo->fk_eclass_member[colno] to the eclass member for the * referencing Var. */ EquivalenceClass * match_eclasses_to_foreign_key_col(PlannerInfo *root, ForeignKeyOptInfo *fkinfo, int colno) { Index var1varno = fkinfo->con_relid; AttrNumber var1attno = fkinfo->conkey[colno]; Index var2varno = fkinfo->ref_relid; AttrNumber var2attno = fkinfo->confkey[colno]; Oid eqop = fkinfo->conpfeqop[colno]; RelOptInfo *rel1 = root->simple_rel_array[var1varno]; RelOptInfo *rel2 = root->simple_rel_array[var2varno]; List *opfamilies = NIL; /* compute only if needed */ Bitmapset *matching_ecs; int i; /* Consider only eclasses mentioning both relations */ Assert(root->ec_merging_done); Assert(IS_SIMPLE_REL(rel1)); Assert(IS_SIMPLE_REL(rel2)); matching_ecs = bms_intersect(rel1->eclass_indexes, rel2->eclass_indexes); i = -1; while ((i = bms_next_member(matching_ecs, i)) >= 0) { EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i); EquivalenceMember *item1_em = NULL; EquivalenceMember *item2_em = NULL; ListCell *lc2; /* Never match to a volatile EC */ if (ec->ec_has_volatile) continue; /* Note: it seems okay to match to "broken" eclasses here */ foreach(lc2, ec->ec_members) { EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2); Var *var; if (em->em_is_child) continue; /* ignore children here */ /* EM must be a Var, possibly with RelabelType */ var = (Var *) em->em_expr; while (var && IsA(var, RelabelType)) var = (Var *) ((RelabelType *) var)->arg; if (!(var && IsA(var, Var))) continue; /* Match? */ if (var->varno == var1varno && var->varattno == var1attno) item1_em = em; else if (var->varno == var2varno && var->varattno == var2attno) item2_em = em; /* Have we found both PK and FK column in this EC? */ if (item1_em && item2_em) { /* * Succeed if eqop matches EC's opfamilies. We could test * this before scanning the members, but it's probably cheaper * to test for member matches first. */ if (opfamilies == NIL) /* compute if we didn't already */ opfamilies = get_mergejoin_opfamilies(eqop); if (equal(opfamilies, ec->ec_opfamilies)) { fkinfo->eclass[colno] = ec; fkinfo->fk_eclass_member[colno] = item2_em; return ec; } /* Otherwise, done with this EC, move on to the next */ break; } } } return NULL; } /* * find_derived_clause_for_ec_member * Search for a previously-derived clause mentioning the given EM. * * The eclass should be an ec_has_const EC, of which the EM is a non-const * member. This should ensure there is just one derived clause mentioning * the EM (and equating it to a constant). * Returns NULL if no such clause can be found. */ RestrictInfo * find_derived_clause_for_ec_member(EquivalenceClass *ec, EquivalenceMember *em) { ListCell *lc; Assert(ec->ec_has_const); Assert(!em->em_is_const); foreach(lc, ec->ec_derives) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc); /* * generate_base_implied_equalities_const will have put non-const * members on the left side of derived clauses. */ if (rinfo->left_em == em) return rinfo; } return NULL; } /* * add_child_rel_equivalences * Search for EC members that reference the root parent of child_rel, and * add transformed members referencing the child_rel. * * Note that this function won't be called at all unless we have at least some * reason to believe that the EC members it generates will be useful. * * parent_rel and child_rel could be derived from appinfo, but since the * caller has already computed them, we might as well just pass them in. * * The passed-in AppendRelInfo is not used when the parent_rel is not a * top-level baserel, since it shows the mapping from the parent_rel but * we need to translate EC expressions that refer to the top-level parent. * Using it is faster than using adjust_appendrel_attrs_multilevel(), though, * so we prefer it when we can. */ void add_child_rel_equivalences(PlannerInfo *root, AppendRelInfo *appinfo, RelOptInfo *parent_rel, RelOptInfo *child_rel) { Relids top_parent_relids = child_rel->top_parent_relids; Relids child_relids = child_rel->relids; int i; /* * EC merging should be complete already, so we can use the parent rel's * eclass_indexes to avoid searching all of root->eq_classes. */ Assert(root->ec_merging_done); Assert(IS_SIMPLE_REL(parent_rel)); i = -1; while ((i = bms_next_member(parent_rel->eclass_indexes, i)) >= 0) { EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i); int num_members; /* * If this EC contains a volatile expression, then generating child * EMs would be downright dangerous, so skip it. We rely on a * volatile EC having only one EM. */ if (cur_ec->ec_has_volatile) continue; /* Sanity check eclass_indexes only contain ECs for parent_rel */ Assert(bms_is_subset(top_parent_relids, cur_ec->ec_relids)); /* * We don't use foreach() here because there's no point in scanning * newly-added child members, so we can stop after the last * pre-existing EC member. */ num_members = list_length(cur_ec->ec_members); for (int pos = 0; pos < num_members; pos++) { EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos); if (cur_em->em_is_const) continue; /* ignore consts here */ /* * We consider only original EC members here, not * already-transformed child members. Otherwise, if some original * member expression references more than one appendrel, we'd get * an O(N^2) explosion of useless derived expressions for * combinations of children. (But add_child_join_rel_equivalences * may add targeted combinations for partitionwise-join purposes.) */ if (cur_em->em_is_child) continue; /* ignore children here */ /* Does this member reference child's topmost parent rel? */ if (bms_overlap(cur_em->em_relids, top_parent_relids)) { /* Yes, generate transformed child version */ Expr *child_expr; Relids new_relids; Relids new_nullable_relids; if (parent_rel->reloptkind == RELOPT_BASEREL) { /* Simple single-level transformation */ child_expr = (Expr *) adjust_appendrel_attrs(root, (Node *) cur_em->em_expr, 1, &appinfo); } else { /* Must do multi-level transformation */ child_expr = (Expr *) adjust_appendrel_attrs_multilevel(root, (Node *) cur_em->em_expr, child_relids, top_parent_relids); } /* * Transform em_relids to match. Note we do *not* do * pull_varnos(child_expr) here, as for example the * transformation might have substituted a constant, but we * don't want the child member to be marked as constant. */ new_relids = bms_difference(cur_em->em_relids, top_parent_relids); new_relids = bms_add_members(new_relids, child_relids); /* * And likewise for nullable_relids. Note this code assumes * parent and child relids are singletons. */ new_nullable_relids = cur_em->em_nullable_relids; if (bms_overlap(new_nullable_relids, top_parent_relids)) { new_nullable_relids = bms_difference(new_nullable_relids, top_parent_relids); new_nullable_relids = bms_add_members(new_nullable_relids, child_relids); } (void) add_eq_member(cur_ec, child_expr, new_relids, new_nullable_relids, true, cur_em->em_datatype); /* Record this EC index for the child rel */ child_rel->eclass_indexes = bms_add_member(child_rel->eclass_indexes, i); } } } } /* * add_child_join_rel_equivalences * Like add_child_rel_equivalences(), but for joinrels * * Here we find the ECs relevant to the top parent joinrel and add transformed * member expressions that refer to this child joinrel. * * Note that this function won't be called at all unless we have at least some * reason to believe that the EC members it generates will be useful. */ void add_child_join_rel_equivalences(PlannerInfo *root, int nappinfos, AppendRelInfo **appinfos, RelOptInfo *parent_joinrel, RelOptInfo *child_joinrel) { Relids top_parent_relids = child_joinrel->top_parent_relids; Relids child_relids = child_joinrel->relids; Bitmapset *matching_ecs; MemoryContext oldcontext; int i; Assert(IS_JOIN_REL(child_joinrel) && IS_JOIN_REL(parent_joinrel)); /* We need consider only ECs that mention the parent joinrel */ matching_ecs = get_eclass_indexes_for_relids(root, top_parent_relids); /* * If we're being called during GEQO join planning, we still have to * create any new EC members in the main planner context, to avoid having * a corrupt EC data structure after the GEQO context is reset. This is * problematic since we'll leak memory across repeated GEQO cycles. For * now, though, bloat is better than crash. If it becomes a real issue * we'll have to do something to avoid generating duplicate EC members. */ oldcontext = MemoryContextSwitchTo(root->planner_cxt); i = -1; while ((i = bms_next_member(matching_ecs, i)) >= 0) { EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i); int num_members; /* * If this EC contains a volatile expression, then generating child * EMs would be downright dangerous, so skip it. We rely on a * volatile EC having only one EM. */ if (cur_ec->ec_has_volatile) continue; /* Sanity check on get_eclass_indexes_for_relids result */ Assert(bms_overlap(top_parent_relids, cur_ec->ec_relids)); /* * We don't use foreach() here because there's no point in scanning * newly-added child members, so we can stop after the last * pre-existing EC member. */ num_members = list_length(cur_ec->ec_members); for (int pos = 0; pos < num_members; pos++) { EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos); if (cur_em->em_is_const) continue; /* ignore consts here */ /* * We consider only original EC members here, not * already-transformed child members. */ if (cur_em->em_is_child) continue; /* ignore children here */ /* * We may ignore expressions that reference a single baserel, * because add_child_rel_equivalences should have handled them. */ if (bms_membership(cur_em->em_relids) != BMS_MULTIPLE) continue; /* Does this member reference child's topmost parent rel? */ if (bms_overlap(cur_em->em_relids, top_parent_relids)) { /* Yes, generate transformed child version */ Expr *child_expr; Relids new_relids; Relids new_nullable_relids; if (parent_joinrel->reloptkind == RELOPT_JOINREL) { /* Simple single-level transformation */ child_expr = (Expr *) adjust_appendrel_attrs(root, (Node *) cur_em->em_expr, nappinfos, appinfos); } else { /* Must do multi-level transformation */ Assert(parent_joinrel->reloptkind == RELOPT_OTHER_JOINREL); child_expr = (Expr *) adjust_appendrel_attrs_multilevel(root, (Node *) cur_em->em_expr, child_relids, top_parent_relids); } /* * Transform em_relids to match. Note we do *not* do * pull_varnos(child_expr) here, as for example the * transformation might have substituted a constant, but we * don't want the child member to be marked as constant. */ new_relids = bms_difference(cur_em->em_relids, top_parent_relids); new_relids = bms_add_members(new_relids, child_relids); /* * For nullable_relids, we must selectively replace parent * nullable relids with child ones. */ new_nullable_relids = cur_em->em_nullable_relids; if (bms_overlap(new_nullable_relids, top_parent_relids)) new_nullable_relids = adjust_child_relids_multilevel(root, new_nullable_relids, child_relids, top_parent_relids); (void) add_eq_member(cur_ec, child_expr, new_relids, new_nullable_relids, true, cur_em->em_datatype); } } } MemoryContextSwitchTo(oldcontext); } /* * generate_implied_equalities_for_column * Create EC-derived joinclauses usable with a specific column. * * This is used by indxpath.c to extract potentially indexable joinclauses * from ECs, and can be used by foreign data wrappers for similar purposes. * We assume that only expressions in Vars of a single table are of interest, * but the caller provides a callback function to identify exactly which * such expressions it would like to know about. * * We assume that any given table/index column could appear in only one EC. * (This should be true in all but the most pathological cases, and if it * isn't, we stop on the first match anyway.) Therefore, what we return * is a redundant list of clauses equating the table/index column to each of * the other-relation values it is known to be equal to. Any one of * these clauses can be used to create a parameterized path, and there * is no value in using more than one. (But it *is* worthwhile to create * a separate parameterized path for each one, since that leads to different * join orders.) * * The caller can pass a Relids set of rels we aren't interested in joining * to, so as to save the work of creating useless clauses. */ List * generate_implied_equalities_for_column(PlannerInfo *root, RelOptInfo *rel, ec_matches_callback_type callback, void *callback_arg, Relids prohibited_rels) { List *result = NIL; bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL); Relids parent_relids; int i; /* Should be OK to rely on eclass_indexes */ Assert(root->ec_merging_done); /* Indexes are available only on base or "other" member relations. */ Assert(IS_SIMPLE_REL(rel)); /* If it's a child rel, we'll need to know what its parent(s) are */ if (is_child_rel) parent_relids = find_childrel_parents(root, rel); else parent_relids = NULL; /* not used, but keep compiler quiet */ i = -1; while ((i = bms_next_member(rel->eclass_indexes, i)) >= 0) { EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i); EquivalenceMember *cur_em; ListCell *lc2; /* Sanity check eclass_indexes only contain ECs for rel */ Assert(is_child_rel || bms_is_subset(rel->relids, cur_ec->ec_relids)); /* * Won't generate joinclauses if const or single-member (the latter * test covers the volatile case too) */ if (cur_ec->ec_has_const || list_length(cur_ec->ec_members) <= 1) continue; /* * Scan members, looking for a match to the target column. Note that * child EC members are considered, but only when they belong to the * target relation. (Unlike regular members, the same expression * could be a child member of more than one EC. Therefore, it's * potentially order-dependent which EC a child relation's target * column gets matched to. This is annoying but it only happens in * corner cases, so for now we live with just reporting the first * match. See also get_eclass_for_sort_expr.) */ cur_em = NULL; foreach(lc2, cur_ec->ec_members) { cur_em = (EquivalenceMember *) lfirst(lc2); if (bms_equal(cur_em->em_relids, rel->relids) && callback(root, rel, cur_ec, cur_em, callback_arg)) break; cur_em = NULL; } if (!cur_em) continue; /* * Found our match. Scan the other EC members and attempt to generate * joinclauses. */ foreach(lc2, cur_ec->ec_members) { EquivalenceMember *other_em = (EquivalenceMember *) lfirst(lc2); Oid eq_op; RestrictInfo *rinfo; if (other_em->em_is_child) continue; /* ignore children here */ /* Make sure it'll be a join to a different rel */ if (other_em == cur_em || bms_overlap(other_em->em_relids, rel->relids)) continue; /* Forget it if caller doesn't want joins to this rel */ if (bms_overlap(other_em->em_relids, prohibited_rels)) continue; /* * Also, if this is a child rel, avoid generating a useless join * to its parent rel(s). */ if (is_child_rel && bms_overlap(parent_relids, other_em->em_relids)) continue; eq_op = select_equality_operator(cur_ec, cur_em->em_datatype, other_em->em_datatype); if (!OidIsValid(eq_op)) continue; /* set parent_ec to mark as redundant with other joinclauses */ rinfo = create_join_clause(root, cur_ec, eq_op, cur_em, other_em, cur_ec); result = lappend(result, rinfo); } /* * If somehow we failed to create any join clauses, we might as well * keep scanning the ECs for another match. But if we did make any, * we're done, because we don't want to return non-redundant clauses. */ if (result) break; } return result; } /* * have_relevant_eclass_joinclause * Detect whether there is an EquivalenceClass that could produce * a joinclause involving the two given relations. * * This is essentially a very cut-down version of * generate_join_implied_equalities(). Note it's OK to occasionally say "yes" * incorrectly. Hence we don't bother with details like whether the lack of a * cross-type operator might prevent the clause from actually being generated. */ bool have_relevant_eclass_joinclause(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2) { Bitmapset *matching_ecs; int i; /* Examine only eclasses mentioning both rel1 and rel2 */ matching_ecs = get_common_eclass_indexes(root, rel1->relids, rel2->relids); i = -1; while ((i = bms_next_member(matching_ecs, i)) >= 0) { EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i); /* * Sanity check that get_common_eclass_indexes gave only ECs * containing both rels. */ Assert(bms_overlap(rel1->relids, ec->ec_relids)); Assert(bms_overlap(rel2->relids, ec->ec_relids)); /* * Won't generate joinclauses if single-member (this test covers the * volatile case too) */ if (list_length(ec->ec_members) <= 1) continue; /* * We do not need to examine the individual members of the EC, because * all that we care about is whether each rel overlaps the relids of * at least one member, and get_common_eclass_indexes() and the single * member check above are sufficient to prove that. (As with * have_relevant_joinclause(), it is not necessary that the EC be able * to form a joinclause relating exactly the two given rels, only that * it be able to form a joinclause mentioning both, and this will * surely be true if both of them overlap ec_relids.) * * Note we don't test ec_broken; if we did, we'd need a separate code * path to look through ec_sources. Checking the membership anyway is * OK as a possibly-overoptimistic heuristic. * * We don't test ec_has_const either, even though a const eclass won't * generate real join clauses. This is because if we had "WHERE a.x = * b.y and a.x = 42", it is worth considering a join between a and b, * since the join result is likely to be small even though it'll end * up being an unqualified nestloop. */ return true; } return false; } /* * has_relevant_eclass_joinclause * Detect whether there is an EquivalenceClass that could produce * a joinclause involving the given relation and anything else. * * This is the same as have_relevant_eclass_joinclause with the other rel * implicitly defined as "everything else in the query". */ bool has_relevant_eclass_joinclause(PlannerInfo *root, RelOptInfo *rel1) { Bitmapset *matched_ecs; int i; /* Examine only eclasses mentioning rel1 */ matched_ecs = get_eclass_indexes_for_relids(root, rel1->relids); i = -1; while ((i = bms_next_member(matched_ecs, i)) >= 0) { EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i); /* * Won't generate joinclauses if single-member (this test covers the * volatile case too) */ if (list_length(ec->ec_members) <= 1) continue; /* * Per the comment in have_relevant_eclass_joinclause, it's sufficient * to find an EC that mentions both this rel and some other rel. */ if (!bms_is_subset(ec->ec_relids, rel1->relids)) return true; } return false; } /* * eclass_useful_for_merging * Detect whether the EC could produce any mergejoinable join clauses * against the specified relation. * * This is just a heuristic test and doesn't have to be exact; it's better * to say "yes" incorrectly than "no". Hence we don't bother with details * like whether the lack of a cross-type operator might prevent the clause * from actually being generated. */ bool eclass_useful_for_merging(PlannerInfo *root, EquivalenceClass *eclass, RelOptInfo *rel) { Relids relids; ListCell *lc; Assert(!eclass->ec_merged); /* * Won't generate joinclauses if const or single-member (the latter test * covers the volatile case too) */ if (eclass->ec_has_const || list_length(eclass->ec_members) <= 1) return false; /* * Note we don't test ec_broken; if we did, we'd need a separate code path * to look through ec_sources. Checking the members anyway is OK as a * possibly-overoptimistic heuristic. */ /* If specified rel is a child, we must consider the topmost parent rel */ if (IS_OTHER_REL(rel)) { Assert(!bms_is_empty(rel->top_parent_relids)); relids = rel->top_parent_relids; } else relids = rel->relids; /* If rel already includes all members of eclass, no point in searching */ if (bms_is_subset(eclass->ec_relids, relids)) return false; /* To join, we need a member not in the given rel */ foreach(lc, eclass->ec_members) { EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc); if (cur_em->em_is_child) continue; /* ignore children here */ if (!bms_overlap(cur_em->em_relids, relids)) return true; } return false; } /* * is_redundant_derived_clause * Test whether rinfo is derived from same EC as any clause in clauselist; * if so, it can be presumed to represent a condition that's redundant * with that member of the list. */ bool is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist) { EquivalenceClass *parent_ec = rinfo->parent_ec; ListCell *lc; /* Fail if it's not a potentially-redundant clause from some EC */ if (parent_ec == NULL) return false; foreach(lc, clauselist) { RestrictInfo *otherrinfo = (RestrictInfo *) lfirst(lc); if (otherrinfo->parent_ec == parent_ec) return true; } return false; } /* * is_redundant_with_indexclauses * Test whether rinfo is redundant with any clause in the IndexClause * list. Here, for convenience, we test both simple identity and * whether it is derived from the same EC as any member of the list. */ bool is_redundant_with_indexclauses(RestrictInfo *rinfo, List *indexclauses) { EquivalenceClass *parent_ec = rinfo->parent_ec; ListCell *lc; foreach(lc, indexclauses) { IndexClause *iclause = lfirst_node(IndexClause, lc); RestrictInfo *otherrinfo = iclause->rinfo; /* If indexclause is lossy, it won't enforce the condition exactly */ if (iclause->lossy) continue; /* Match if it's same clause (pointer equality should be enough) */ if (rinfo == otherrinfo) return true; /* Match if derived from same EC */ if (parent_ec && otherrinfo->parent_ec == parent_ec) return true; /* * No need to look at the derived clauses in iclause->indexquals; they * couldn't match if the parent clause didn't. */ } return false; } /* * get_eclass_indexes_for_relids * Build and return a Bitmapset containing the indexes into root's * eq_classes list for all eclasses that mention any of these relids */ static Bitmapset * get_eclass_indexes_for_relids(PlannerInfo *root, Relids relids) { Bitmapset *ec_indexes = NULL; int i = -1; /* Should be OK to rely on eclass_indexes */ Assert(root->ec_merging_done); while ((i = bms_next_member(relids, i)) > 0) { RelOptInfo *rel = root->simple_rel_array[i]; ec_indexes = bms_add_members(ec_indexes, rel->eclass_indexes); } return ec_indexes; } /* * get_common_eclass_indexes * Build and return a Bitmapset containing the indexes into root's * eq_classes list for all eclasses that mention rels in both * relids1 and relids2. */ static Bitmapset * get_common_eclass_indexes(PlannerInfo *root, Relids relids1, Relids relids2) { Bitmapset *rel1ecs; Bitmapset *rel2ecs; int relid; rel1ecs = get_eclass_indexes_for_relids(root, relids1); /* * We can get away with just using the relation's eclass_indexes directly * when relids2 is a singleton set. */ if (bms_get_singleton_member(relids2, &relid)) rel2ecs = root->simple_rel_array[relid]->eclass_indexes; else rel2ecs = get_eclass_indexes_for_relids(root, relids2); /* Calculate and return the common EC indexes, recycling the left input. */ return bms_int_members(rel1ecs, rel2ecs); }