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Diffstat (limited to 'src/backend/optimizer/path/equivclass.c')
| -rw-r--r-- | src/backend/optimizer/path/equivclass.c | 3226 |
1 files changed, 3226 insertions, 0 deletions
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c new file mode 100644 index 0000000..9f39f46 --- /dev/null +++ b/src/backend/optimizer/path/equivclass.c @@ -0,0 +1,3226 @@ +/*------------------------------------------------------------------------- + * + * equivclass.c + * Routines for managing EquivalenceClasses + * + * See src/backend/optimizer/README for discussion of EquivalenceClasses. + * + * + * Portions Copyright (c) 1996-2022, 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 <limits.h> + +#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; +} + +/* + * 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 an 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); +} |