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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:15:05 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:15:05 +0000
commit46651ce6fe013220ed397add242004d764fc0153 (patch)
tree6e5299f990f88e60174a1d3ae6e48eedd2688b2b /src/backend/optimizer/path/equivclass.c
parentInitial commit. (diff)
downloadpostgresql-14-upstream.tar.xz
postgresql-14-upstream.zip
Adding upstream version 14.5.upstream/14.5upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/backend/optimizer/path/equivclass.c')
-rw-r--r--src/backend/optimizer/path/equivclass.c3255
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diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c
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+/*-------------------------------------------------------------------------
+ *
+ * equivclass.c
+ * Routines for managing EquivalenceClasses
+ *
+ * See src/backend/optimizer/README for discussion of EquivalenceClasses.
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ * src/backend/optimizer/path/equivclass.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <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;
+}
+
+/*
+ * Find an equivalence class member expression, all of whose Vars, come from
+ * the indicated relation.
+ */
+Expr *
+find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
+{
+ ListCell *lc_em;
+
+ foreach(lc_em, ec->ec_members)
+ {
+ EquivalenceMember *em = lfirst(lc_em);
+
+ if (bms_is_subset(em->em_relids, rel->relids) &&
+ !bms_is_empty(em->em_relids))
+ {
+ /*
+ * If there is more than one equivalence member whose Vars are
+ * taken entirely from this relation, we'll be content to choose
+ * any one of those.
+ */
+ return em->em_expr;
+ }
+ }
+
+ /* We didn't find any suitable equivalence class expression */
+ return NULL;
+}
+
+/*
+ * relation_can_be_sorted_early
+ * Can this relation be sorted on this EC before the final output step?
+ *
+ * To succeed, we must find an EC member that prepare_sort_from_pathkeys knows
+ * how to sort on, given the rel's reltarget as input. There are also a few
+ * additional constraints based on the fact that the desired sort will be done
+ * "early", within the scan/join part of the plan. Also, non-parallel-safe
+ * expressions are ignored if 'require_parallel_safe'.
+ *
+ * At some point we might want to return the identified EquivalenceMember,
+ * but for now, callers only want to know if there is one.
+ */
+bool
+relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
+ EquivalenceClass *ec, bool require_parallel_safe)
+{
+ PathTarget *target = rel->reltarget;
+ EquivalenceMember *em;
+ ListCell *lc;
+
+ /*
+ * Reject volatile ECs immediately; such sorts must always be postponed.
+ */
+ if (ec->ec_has_volatile)
+ return false;
+
+ /*
+ * Try to find an EM directly matching some reltarget member.
+ */
+ foreach(lc, target->exprs)
+ {
+ Expr *targetexpr = (Expr *) lfirst(lc);
+
+ em = find_ec_member_matching_expr(ec, targetexpr, rel->relids);
+ if (!em)
+ continue;
+
+ /*
+ * Reject expressions involving set-returning functions, as those
+ * can't be computed early either. (Note: this test and the following
+ * one are effectively checking properties of targetexpr, so there's
+ * no point in asking whether some other EC member would be better.)
+ */
+ if (expression_returns_set((Node *) em->em_expr))
+ continue;
+
+ /*
+ * If requested, reject expressions that are not parallel-safe. We
+ * check this last because it's a rather expensive test.
+ */
+ if (require_parallel_safe &&
+ !is_parallel_safe(root, (Node *) em->em_expr))
+ continue;
+
+ return true;
+ }
+
+ /*
+ * Try to find a expression computable from the reltarget.
+ */
+ em = find_computable_ec_member(root, ec, target->exprs, rel->relids,
+ require_parallel_safe);
+ if (!em)
+ return false;
+
+ /*
+ * Reject expressions involving set-returning functions, as those can't be
+ * computed early either. (There's no point in looking for another EC
+ * member in this case; since SRFs can't appear in WHERE, they cannot
+ * belong to multi-member ECs.)
+ */
+ if (expression_returns_set((Node *) em->em_expr))
+ return false;
+
+ return true;
+}
+
+/*
+ * generate_base_implied_equalities
+ * Generate any restriction clauses that we can deduce from equivalence
+ * classes.
+ *
+ * When an EC contains pseudoconstants, our strategy is to generate
+ * "member = const1" clauses where const1 is the first constant member, for
+ * every other member (including other constants). If we are able to do this
+ * then we don't need any "var = var" comparisons because we've successfully
+ * constrained all the vars at their points of creation. If we fail to
+ * generate any of these clauses due to lack of cross-type operators, we fall
+ * back to the "ec_broken" strategy described below. (XXX if there are
+ * multiple constants of different types, it's possible that we might succeed
+ * in forming all the required clauses if we started from a different const
+ * member; but this seems a sufficiently hokey corner case to not be worth
+ * spending lots of cycles on.)
+ *
+ * For ECs that contain no pseudoconstants, we generate derived clauses
+ * "member1 = member2" for each pair of members belonging to the same base
+ * relation (actually, if there are more than two for the same base relation,
+ * we only need enough clauses to link each to each other). This provides
+ * the base case for the recursion: each row emitted by a base relation scan
+ * will constrain all computable members of the EC to be equal. As each
+ * join path is formed, we'll add additional derived clauses on-the-fly
+ * to maintain this invariant (see generate_join_implied_equalities).
+ *
+ * If the opfamilies used by the EC do not provide complete sets of cross-type
+ * equality operators, it is possible that we will fail to generate a clause
+ * that must be generated to maintain the invariant. (An example: given
+ * "WHERE a.x = b.y AND b.y = a.z", the scheme breaks down if we cannot
+ * generate "a.x = a.z" as a restriction clause for A.) In this case we mark
+ * the EC "ec_broken" and fall back to regurgitating its original source
+ * RestrictInfos at appropriate times. We do not try to retract any derived
+ * clauses already generated from the broken EC, so the resulting plan could
+ * be poor due to bad selectivity estimates caused by redundant clauses. But
+ * the correct solution to that is to fix the opfamilies ...
+ *
+ * Equality clauses derived by this function are passed off to
+ * process_implied_equality (in plan/initsplan.c) to be inserted into the
+ * restrictinfo datastructures. Note that this must be called after initial
+ * scanning of the quals and before Path construction begins.
+ *
+ * We make no attempt to avoid generating duplicate RestrictInfos here: we
+ * don't search ec_sources or ec_derives for matches. It doesn't really
+ * seem worth the trouble to do so.
+ */
+void
+generate_base_implied_equalities(PlannerInfo *root)
+{
+ int ec_index;
+ ListCell *lc;
+
+ /*
+ * At this point, we're done absorbing knowledge of equivalences in the
+ * query, so no further EC merging should happen, and ECs remaining in the
+ * eq_classes list can be considered canonical. (But note that it's still
+ * possible for new single-member ECs to be added through
+ * get_eclass_for_sort_expr().)
+ */
+ root->ec_merging_done = true;
+
+ ec_index = 0;
+ foreach(lc, root->eq_classes)
+ {
+ EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
+ bool can_generate_joinclause = false;
+ int i;
+
+ Assert(ec->ec_merged == NULL); /* else shouldn't be in list */
+ Assert(!ec->ec_broken); /* not yet anyway... */
+
+ /*
+ * Generate implied equalities that are restriction clauses.
+ * Single-member ECs won't generate any deductions, either here or at
+ * the join level.
+ */
+ if (list_length(ec->ec_members) > 1)
+ {
+ if (ec->ec_has_const)
+ generate_base_implied_equalities_const(root, ec);
+ else
+ generate_base_implied_equalities_no_const(root, ec);
+
+ /* Recover if we failed to generate required derived clauses */
+ if (ec->ec_broken)
+ generate_base_implied_equalities_broken(root, ec);
+
+ /* Detect whether this EC might generate join clauses */
+ can_generate_joinclause =
+ (bms_membership(ec->ec_relids) == BMS_MULTIPLE);
+ }
+
+ /*
+ * Mark the base rels cited in each eclass (which should all exist by
+ * now) with the eq_classes indexes of all eclasses mentioning them.
+ * This will let us avoid searching in subsequent lookups. While
+ * we're at it, we can mark base rels that have pending eclass joins;
+ * this is a cheap version of has_relevant_eclass_joinclause().
+ */
+ i = -1;
+ while ((i = bms_next_member(ec->ec_relids, i)) > 0)
+ {
+ RelOptInfo *rel = root->simple_rel_array[i];
+
+ Assert(rel->reloptkind == RELOPT_BASEREL);
+
+ rel->eclass_indexes = bms_add_member(rel->eclass_indexes,
+ ec_index);
+
+ if (can_generate_joinclause)
+ rel->has_eclass_joins = true;
+ }
+
+ ec_index++;
+ }
+}
+
+/*
+ * generate_base_implied_equalities when EC contains pseudoconstant(s)
+ */
+static void
+generate_base_implied_equalities_const(PlannerInfo *root,
+ EquivalenceClass *ec)
+{
+ EquivalenceMember *const_em = NULL;
+ ListCell *lc;
+
+ /*
+ * In the trivial case where we just had one "var = const" clause, push
+ * the original clause back into the main planner machinery. There is
+ * nothing to be gained by doing it differently, and we save the effort to
+ * re-build and re-analyze an equality clause that will be exactly
+ * equivalent to the old one.
+ */
+ if (list_length(ec->ec_members) == 2 &&
+ list_length(ec->ec_sources) == 1)
+ {
+ RestrictInfo *restrictinfo = (RestrictInfo *) linitial(ec->ec_sources);
+
+ if (bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
+ {
+ distribute_restrictinfo_to_rels(root, restrictinfo);
+ return;
+ }
+ }
+
+ /*
+ * Find the constant member to use. We prefer an actual constant to
+ * pseudo-constants (such as Params), because the constraint exclusion
+ * machinery might be able to exclude relations on the basis of generated
+ * "var = const" equalities, but "var = param" won't work for that.
+ */
+ foreach(lc, ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
+
+ if (cur_em->em_is_const)
+ {
+ const_em = cur_em;
+ if (IsA(cur_em->em_expr, Const))
+ break;
+ }
+ }
+ Assert(const_em != NULL);
+
+ /* Generate a derived equality against each other member */
+ foreach(lc, ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
+ Oid eq_op;
+ RestrictInfo *rinfo;
+
+ Assert(!cur_em->em_is_child); /* no children yet */
+ if (cur_em == const_em)
+ continue;
+ eq_op = select_equality_operator(ec,
+ cur_em->em_datatype,
+ const_em->em_datatype);
+ if (!OidIsValid(eq_op))
+ {
+ /* failed... */
+ ec->ec_broken = true;
+ break;
+ }
+ rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
+ cur_em->em_expr, const_em->em_expr,
+ bms_copy(ec->ec_relids),
+ bms_union(cur_em->em_nullable_relids,
+ const_em->em_nullable_relids),
+ ec->ec_min_security,
+ ec->ec_below_outer_join,
+ cur_em->em_is_const);
+
+ /*
+ * If the clause didn't degenerate to a constant, fill in the correct
+ * markings for a mergejoinable clause, and save it in ec_derives. (We
+ * will not re-use such clauses directly, but selectivity estimation
+ * may consult the list later. Note that this use of ec_derives does
+ * not overlap with its use for join clauses, since we never generate
+ * join clauses from an ec_has_const eclass.)
+ */
+ if (rinfo && rinfo->mergeopfamilies)
+ {
+ /* it's not redundant, so don't set parent_ec */
+ rinfo->left_ec = rinfo->right_ec = ec;
+ rinfo->left_em = cur_em;
+ rinfo->right_em = const_em;
+ ec->ec_derives = lappend(ec->ec_derives, rinfo);
+ }
+ }
+}
+
+/*
+ * generate_base_implied_equalities when EC contains no pseudoconstants
+ */
+static void
+generate_base_implied_equalities_no_const(PlannerInfo *root,
+ EquivalenceClass *ec)
+{
+ EquivalenceMember **prev_ems;
+ ListCell *lc;
+
+ /*
+ * We scan the EC members once and track the last-seen member for each
+ * base relation. When we see another member of the same base relation,
+ * we generate "prev_em = cur_em". This results in the minimum number of
+ * derived clauses, but it's possible that it will fail when a different
+ * ordering would succeed. XXX FIXME: use a UNION-FIND algorithm similar
+ * to the way we build merged ECs. (Use a list-of-lists for each rel.)
+ */
+ prev_ems = (EquivalenceMember **)
+ palloc0(root->simple_rel_array_size * sizeof(EquivalenceMember *));
+
+ foreach(lc, ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
+ int relid;
+
+ Assert(!cur_em->em_is_child); /* no children yet */
+ if (!bms_get_singleton_member(cur_em->em_relids, &relid))
+ continue;
+ Assert(relid < root->simple_rel_array_size);
+
+ if (prev_ems[relid] != NULL)
+ {
+ EquivalenceMember *prev_em = prev_ems[relid];
+ Oid eq_op;
+ RestrictInfo *rinfo;
+
+ eq_op = select_equality_operator(ec,
+ prev_em->em_datatype,
+ cur_em->em_datatype);
+ if (!OidIsValid(eq_op))
+ {
+ /* failed... */
+ ec->ec_broken = true;
+ break;
+ }
+ rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
+ prev_em->em_expr, cur_em->em_expr,
+ bms_copy(ec->ec_relids),
+ bms_union(prev_em->em_nullable_relids,
+ cur_em->em_nullable_relids),
+ ec->ec_min_security,
+ ec->ec_below_outer_join,
+ false);
+
+ /*
+ * If the clause didn't degenerate to a constant, fill in the
+ * correct markings for a mergejoinable clause. We don't put it
+ * in ec_derives however; we don't currently need to re-find such
+ * clauses, and we don't want to clutter that list with non-join
+ * clauses.
+ */
+ if (rinfo && rinfo->mergeopfamilies)
+ {
+ /* it's not redundant, so don't set parent_ec */
+ rinfo->left_ec = rinfo->right_ec = ec;
+ rinfo->left_em = prev_em;
+ rinfo->right_em = cur_em;
+ }
+ }
+ prev_ems[relid] = cur_em;
+ }
+
+ pfree(prev_ems);
+
+ /*
+ * We also have to make sure that all the Vars used in the member clauses
+ * will be available at any join node we might try to reference them at.
+ * For the moment we force all the Vars to be available at all join nodes
+ * for this eclass. Perhaps this could be improved by doing some
+ * pre-analysis of which members we prefer to join, but it's no worse than
+ * what happened in the pre-8.3 code.
+ */
+ foreach(lc, ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
+ List *vars = pull_var_clause((Node *) cur_em->em_expr,
+ PVC_RECURSE_AGGREGATES |
+ PVC_RECURSE_WINDOWFUNCS |
+ PVC_INCLUDE_PLACEHOLDERS);
+
+ add_vars_to_targetlist(root, vars, ec->ec_relids, false);
+ list_free(vars);
+ }
+}
+
+/*
+ * generate_base_implied_equalities cleanup after failure
+ *
+ * What we must do here is push any zero- or one-relation source RestrictInfos
+ * of the EC back into the main restrictinfo datastructures. Multi-relation
+ * clauses will be regurgitated later by generate_join_implied_equalities().
+ * (We do it this way to maintain continuity with the case that ec_broken
+ * becomes set only after we've gone up a join level or two.) However, for
+ * an EC that contains constants, we can adopt a simpler strategy and just
+ * throw back all the source RestrictInfos immediately; that works because
+ * we know that such an EC can't become broken later. (This rule justifies
+ * ignoring ec_has_const ECs in generate_join_implied_equalities, even when
+ * they are broken.)
+ */
+static void
+generate_base_implied_equalities_broken(PlannerInfo *root,
+ EquivalenceClass *ec)
+{
+ ListCell *lc;
+
+ foreach(lc, ec->ec_sources)
+ {
+ RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
+
+ if (ec->ec_has_const ||
+ bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
+ distribute_restrictinfo_to_rels(root, restrictinfo);
+ }
+}
+
+
+/*
+ * generate_join_implied_equalities
+ * Generate any join clauses that we can deduce from equivalence classes.
+ *
+ * At a join node, we must enforce restriction clauses sufficient to ensure
+ * that all equivalence-class members computable at that node are equal.
+ * Since the set of clauses to enforce can vary depending on which subset
+ * relations are the inputs, we have to compute this afresh for each join
+ * relation pair. Hence a fresh List of RestrictInfo nodes is built and
+ * passed back on each call.
+ *
+ * In addition to its use at join nodes, this can be applied to generate
+ * eclass-based join clauses for use in a parameterized scan of a base rel.
+ * The reason for the asymmetry of specifying the inner rel as a RelOptInfo
+ * and the outer rel by Relids is that this usage occurs before we have
+ * built any join RelOptInfos.
+ *
+ * An annoying special case for parameterized scans is that the inner rel can
+ * be an appendrel child (an "other rel"). In this case we must generate
+ * appropriate clauses using child EC members. add_child_rel_equivalences
+ * must already have been done for the child rel.
+ *
+ * The results are sufficient for use in merge, hash, and plain nestloop join
+ * methods. We do not worry here about selecting clauses that are optimal
+ * for use in a parameterized indexscan. indxpath.c makes its own selections
+ * of clauses to use, and if the ones we pick here are redundant with those,
+ * the extras will be eliminated at createplan time, using the parent_ec
+ * markers that we provide (see is_redundant_derived_clause()).
+ *
+ * Because the same join clauses are likely to be needed multiple times as
+ * we consider different join paths, we avoid generating multiple copies:
+ * whenever we select a particular pair of EquivalenceMembers to join,
+ * we check to see if the pair matches any original clause (in ec_sources)
+ * or previously-built clause (in ec_derives). This saves memory and allows
+ * re-use of information cached in RestrictInfos.
+ *
+ * join_relids should always equal bms_union(outer_relids, inner_rel->relids).
+ * We could simplify this function's API by computing it internally, but in
+ * most current uses, the caller has the value at hand anyway.
+ */
+List *
+generate_join_implied_equalities(PlannerInfo *root,
+ Relids join_relids,
+ Relids outer_relids,
+ RelOptInfo *inner_rel)
+{
+ List *result = NIL;
+ Relids inner_relids = inner_rel->relids;
+ Relids nominal_inner_relids;
+ Relids nominal_join_relids;
+ Bitmapset *matching_ecs;
+ int i;
+
+ /* If inner rel is a child, extra setup work is needed */
+ if (IS_OTHER_REL(inner_rel))
+ {
+ Assert(!bms_is_empty(inner_rel->top_parent_relids));
+
+ /* Fetch relid set for the topmost parent rel */
+ nominal_inner_relids = inner_rel->top_parent_relids;
+ /* ECs will be marked with the parent's relid, not the child's */
+ nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
+ }
+ else
+ {
+ nominal_inner_relids = inner_relids;
+ nominal_join_relids = join_relids;
+ }
+
+ /*
+ * Get all eclasses that mention both inner and outer sides of the join
+ */
+ matching_ecs = get_common_eclass_indexes(root, nominal_inner_relids,
+ outer_relids);
+
+ i = -1;
+ while ((i = bms_next_member(matching_ecs, i)) >= 0)
+ {
+ EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
+ List *sublist = NIL;
+
+ /* ECs containing consts do not need any further enforcement */
+ if (ec->ec_has_const)
+ continue;
+
+ /* Single-member ECs won't generate any deductions */
+ if (list_length(ec->ec_members) <= 1)
+ continue;
+
+ /* Sanity check that this eclass overlaps the join */
+ Assert(bms_overlap(ec->ec_relids, nominal_join_relids));
+
+ if (!ec->ec_broken)
+ sublist = generate_join_implied_equalities_normal(root,
+ ec,
+ join_relids,
+ outer_relids,
+ inner_relids);
+
+ /* Recover if we failed to generate required derived clauses */
+ if (ec->ec_broken)
+ sublist = generate_join_implied_equalities_broken(root,
+ ec,
+ nominal_join_relids,
+ outer_relids,
+ nominal_inner_relids,
+ inner_rel);
+
+ result = list_concat(result, sublist);
+ }
+
+ return result;
+}
+
+/*
+ * generate_join_implied_equalities_for_ecs
+ * As above, but consider only the listed ECs.
+ */
+List *
+generate_join_implied_equalities_for_ecs(PlannerInfo *root,
+ List *eclasses,
+ Relids join_relids,
+ Relids outer_relids,
+ RelOptInfo *inner_rel)
+{
+ List *result = NIL;
+ Relids inner_relids = inner_rel->relids;
+ Relids nominal_inner_relids;
+ Relids nominal_join_relids;
+ ListCell *lc;
+
+ /* If inner rel is a child, extra setup work is needed */
+ if (IS_OTHER_REL(inner_rel))
+ {
+ Assert(!bms_is_empty(inner_rel->top_parent_relids));
+
+ /* Fetch relid set for the topmost parent rel */
+ nominal_inner_relids = inner_rel->top_parent_relids;
+ /* ECs will be marked with the parent's relid, not the child's */
+ nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
+ }
+ else
+ {
+ nominal_inner_relids = inner_relids;
+ nominal_join_relids = join_relids;
+ }
+
+ foreach(lc, eclasses)
+ {
+ EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
+ List *sublist = NIL;
+
+ /* ECs containing consts do not need any further enforcement */
+ if (ec->ec_has_const)
+ continue;
+
+ /* Single-member ECs won't generate any deductions */
+ if (list_length(ec->ec_members) <= 1)
+ continue;
+
+ /* We can quickly ignore any that don't overlap the join, too */
+ if (!bms_overlap(ec->ec_relids, nominal_join_relids))
+ continue;
+
+ if (!ec->ec_broken)
+ sublist = generate_join_implied_equalities_normal(root,
+ ec,
+ join_relids,
+ outer_relids,
+ inner_relids);
+
+ /* Recover if we failed to generate required derived clauses */
+ if (ec->ec_broken)
+ sublist = generate_join_implied_equalities_broken(root,
+ ec,
+ nominal_join_relids,
+ outer_relids,
+ nominal_inner_relids,
+ inner_rel);
+
+ result = list_concat(result, sublist);
+ }
+
+ return result;
+}
+
+/*
+ * generate_join_implied_equalities for a still-valid EC
+ */
+static List *
+generate_join_implied_equalities_normal(PlannerInfo *root,
+ EquivalenceClass *ec,
+ Relids join_relids,
+ Relids outer_relids,
+ Relids inner_relids)
+{
+ List *result = NIL;
+ List *new_members = NIL;
+ List *outer_members = NIL;
+ List *inner_members = NIL;
+ ListCell *lc1;
+
+ /*
+ * First, scan the EC to identify member values that are computable at the
+ * outer rel, at the inner rel, or at this relation but not in either
+ * input rel. The outer-rel members should already be enforced equal,
+ * likewise for the inner-rel members. We'll need to create clauses to
+ * enforce that any newly computable members are all equal to each other
+ * as well as to at least one input member, plus enforce at least one
+ * outer-rel member equal to at least one inner-rel member.
+ */
+ foreach(lc1, ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
+
+ /*
+ * We don't need to check explicitly for child EC members. This test
+ * against join_relids will cause them to be ignored except when
+ * considering a child inner rel, which is what we want.
+ */
+ if (!bms_is_subset(cur_em->em_relids, join_relids))
+ continue; /* not computable yet, or wrong child */
+
+ if (bms_is_subset(cur_em->em_relids, outer_relids))
+ outer_members = lappend(outer_members, cur_em);
+ else if (bms_is_subset(cur_em->em_relids, inner_relids))
+ inner_members = lappend(inner_members, cur_em);
+ else
+ new_members = lappend(new_members, cur_em);
+ }
+
+ /*
+ * First, select the joinclause if needed. We can equate any one outer
+ * member to any one inner member, but we have to find a datatype
+ * combination for which an opfamily member operator exists. If we have
+ * choices, we prefer simple Var members (possibly with RelabelType) since
+ * these are (a) cheapest to compute at runtime and (b) most likely to
+ * have useful statistics. Also, prefer operators that are also
+ * hashjoinable.
+ */
+ if (outer_members && inner_members)
+ {
+ EquivalenceMember *best_outer_em = NULL;
+ EquivalenceMember *best_inner_em = NULL;
+ Oid best_eq_op = InvalidOid;
+ int best_score = -1;
+ RestrictInfo *rinfo;
+
+ foreach(lc1, outer_members)
+ {
+ EquivalenceMember *outer_em = (EquivalenceMember *) lfirst(lc1);
+ ListCell *lc2;
+
+ foreach(lc2, inner_members)
+ {
+ EquivalenceMember *inner_em = (EquivalenceMember *) lfirst(lc2);
+ Oid eq_op;
+ int score;
+
+ eq_op = select_equality_operator(ec,
+ outer_em->em_datatype,
+ inner_em->em_datatype);
+ if (!OidIsValid(eq_op))
+ continue;
+ score = 0;
+ if (IsA(outer_em->em_expr, Var) ||
+ (IsA(outer_em->em_expr, RelabelType) &&
+ IsA(((RelabelType *) outer_em->em_expr)->arg, Var)))
+ score++;
+ if (IsA(inner_em->em_expr, Var) ||
+ (IsA(inner_em->em_expr, RelabelType) &&
+ IsA(((RelabelType *) inner_em->em_expr)->arg, Var)))
+ score++;
+ if (op_hashjoinable(eq_op,
+ exprType((Node *) outer_em->em_expr)))
+ score++;
+ if (score > best_score)
+ {
+ best_outer_em = outer_em;
+ best_inner_em = inner_em;
+ best_eq_op = eq_op;
+ best_score = score;
+ if (best_score == 3)
+ break; /* no need to look further */
+ }
+ }
+ if (best_score == 3)
+ break; /* no need to look further */
+ }
+ if (best_score < 0)
+ {
+ /* failed... */
+ ec->ec_broken = true;
+ return NIL;
+ }
+
+ /*
+ * Create clause, setting parent_ec to mark it as redundant with other
+ * joinclauses
+ */
+ rinfo = create_join_clause(root, ec, best_eq_op,
+ best_outer_em, best_inner_em,
+ ec);
+
+ result = lappend(result, rinfo);
+ }
+
+ /*
+ * Now deal with building restrictions for any expressions that involve
+ * Vars from both sides of the join. We have to equate all of these to
+ * each other as well as to at least one old member (if any).
+ *
+ * XXX as in generate_base_implied_equalities_no_const, we could be a lot
+ * smarter here to avoid unnecessary failures in cross-type situations.
+ * For now, use the same left-to-right method used there.
+ */
+ if (new_members)
+ {
+ List *old_members = list_concat(outer_members, inner_members);
+ EquivalenceMember *prev_em = NULL;
+ RestrictInfo *rinfo;
+
+ /* For now, arbitrarily take the first old_member as the one to use */
+ if (old_members)
+ new_members = lappend(new_members, linitial(old_members));
+
+ foreach(lc1, new_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
+
+ if (prev_em != NULL)
+ {
+ Oid eq_op;
+
+ eq_op = select_equality_operator(ec,
+ prev_em->em_datatype,
+ cur_em->em_datatype);
+ if (!OidIsValid(eq_op))
+ {
+ /* failed... */
+ ec->ec_broken = true;
+ return NIL;
+ }
+ /* do NOT set parent_ec, this qual is not redundant! */
+ rinfo = create_join_clause(root, ec, eq_op,
+ prev_em, cur_em,
+ NULL);
+
+ result = lappend(result, rinfo);
+ }
+ prev_em = cur_em;
+ }
+ }
+
+ return result;
+}
+
+/*
+ * generate_join_implied_equalities cleanup after failure
+ *
+ * Return any original RestrictInfos that are enforceable at this join.
+ *
+ * In the case of a child inner relation, we have to translate the
+ * original RestrictInfos from parent to child Vars.
+ */
+static List *
+generate_join_implied_equalities_broken(PlannerInfo *root,
+ EquivalenceClass *ec,
+ Relids nominal_join_relids,
+ Relids outer_relids,
+ Relids nominal_inner_relids,
+ RelOptInfo *inner_rel)
+{
+ List *result = NIL;
+ ListCell *lc;
+
+ foreach(lc, ec->ec_sources)
+ {
+ RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
+ Relids clause_relids = restrictinfo->required_relids;
+
+ if (bms_is_subset(clause_relids, nominal_join_relids) &&
+ !bms_is_subset(clause_relids, outer_relids) &&
+ !bms_is_subset(clause_relids, nominal_inner_relids))
+ result = lappend(result, restrictinfo);
+ }
+
+ /*
+ * If we have to translate, just brute-force apply adjust_appendrel_attrs
+ * to all the RestrictInfos at once. This will result in returning
+ * RestrictInfos that are not listed in ec_derives, but there shouldn't be
+ * any duplication, and it's a sufficiently narrow corner case that we
+ * shouldn't sweat too much over it anyway.
+ *
+ * Since inner_rel might be an indirect descendant of the baserel
+ * mentioned in the ec_sources clauses, we have to be prepared to apply
+ * multiple levels of Var translation.
+ */
+ if (IS_OTHER_REL(inner_rel) && result != NIL)
+ result = (List *) adjust_appendrel_attrs_multilevel(root,
+ (Node *) result,
+ inner_rel->relids,
+ inner_rel->top_parent_relids);
+
+ return result;
+}
+
+
+/*
+ * select_equality_operator
+ * Select a suitable equality operator for comparing two EC members
+ *
+ * Returns InvalidOid if no operator can be found for this datatype combination
+ */
+static Oid
+select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype)
+{
+ ListCell *lc;
+
+ foreach(lc, ec->ec_opfamilies)
+ {
+ Oid opfamily = lfirst_oid(lc);
+ Oid opno;
+
+ opno = get_opfamily_member(opfamily, lefttype, righttype,
+ BTEqualStrategyNumber);
+ if (!OidIsValid(opno))
+ continue;
+ /* If no barrier quals in query, don't worry about leaky operators */
+ if (ec->ec_max_security == 0)
+ return opno;
+ /* Otherwise, insist that selected operators be leakproof */
+ if (get_func_leakproof(get_opcode(opno)))
+ return opno;
+ }
+ return InvalidOid;
+}
+
+
+/*
+ * create_join_clause
+ * Find or make a RestrictInfo comparing the two given EC members
+ * with the given operator.
+ *
+ * parent_ec is either equal to ec (if the clause is a potentially-redundant
+ * join clause) or NULL (if not). We have to treat this as part of the
+ * match requirements --- it's possible that a clause comparing the same two
+ * EMs is a join clause in one join path and a restriction clause in another.
+ */
+static RestrictInfo *
+create_join_clause(PlannerInfo *root,
+ EquivalenceClass *ec, Oid opno,
+ EquivalenceMember *leftem,
+ EquivalenceMember *rightem,
+ EquivalenceClass *parent_ec)
+{
+ RestrictInfo *rinfo;
+ ListCell *lc;
+ MemoryContext oldcontext;
+
+ /*
+ * Search to see if we already built a RestrictInfo for this pair of
+ * EquivalenceMembers. We can use either original source clauses or
+ * previously-derived clauses. The check on opno is probably redundant,
+ * but be safe ...
+ */
+ foreach(lc, ec->ec_sources)
+ {
+ rinfo = (RestrictInfo *) lfirst(lc);
+ if (rinfo->left_em == leftem &&
+ rinfo->right_em == rightem &&
+ rinfo->parent_ec == parent_ec &&
+ opno == ((OpExpr *) rinfo->clause)->opno)
+ return rinfo;
+ }
+
+ foreach(lc, ec->ec_derives)
+ {
+ rinfo = (RestrictInfo *) lfirst(lc);
+ if (rinfo->left_em == leftem &&
+ rinfo->right_em == rightem &&
+ rinfo->parent_ec == parent_ec &&
+ opno == ((OpExpr *) rinfo->clause)->opno)
+ return rinfo;
+ }
+
+ /*
+ * Not there, so build it, in planner context so we can re-use it. (Not
+ * important in normal planning, but definitely so in GEQO.)
+ */
+ oldcontext = MemoryContextSwitchTo(root->planner_cxt);
+
+ rinfo = build_implied_join_equality(root,
+ opno,
+ ec->ec_collation,
+ leftem->em_expr,
+ rightem->em_expr,
+ bms_union(leftem->em_relids,
+ rightem->em_relids),
+ bms_union(leftem->em_nullable_relids,
+ rightem->em_nullable_relids),
+ ec->ec_min_security);
+
+ /* Mark the clause as redundant, or not */
+ rinfo->parent_ec = parent_ec;
+
+ /*
+ * We know the correct values for left_ec/right_ec, ie this particular EC,
+ * so we can just set them directly instead of forcing another lookup.
+ */
+ rinfo->left_ec = ec;
+ rinfo->right_ec = ec;
+
+ /* Mark it as usable with these EMs */
+ rinfo->left_em = leftem;
+ rinfo->right_em = rightem;
+ /* and save it for possible re-use */
+ ec->ec_derives = lappend(ec->ec_derives, rinfo);
+
+ MemoryContextSwitchTo(oldcontext);
+
+ return rinfo;
+}
+
+
+/*
+ * reconsider_outer_join_clauses
+ * Re-examine any outer-join clauses that were set aside by
+ * distribute_qual_to_rels(), and see if we can derive any
+ * EquivalenceClasses from them. Then, if they were not made
+ * redundant, push them out into the regular join-clause lists.
+ *
+ * When we have mergejoinable clauses A = B that are outer-join clauses,
+ * we can't blindly combine them with other clauses A = C to deduce B = C,
+ * since in fact the "equality" A = B won't necessarily hold above the
+ * outer join (one of the variables might be NULL instead). Nonetheless
+ * there are cases where we can add qual clauses using transitivity.
+ *
+ * One case that we look for here is an outer-join clause OUTERVAR = INNERVAR
+ * for which there is also an equivalence clause OUTERVAR = CONSTANT.
+ * It is safe and useful to push a clause INNERVAR = CONSTANT into the
+ * evaluation of the inner (nullable) relation, because any inner rows not
+ * meeting this condition will not contribute to the outer-join result anyway.
+ * (Any outer rows they could join to will be eliminated by the pushed-down
+ * equivalence clause.)
+ *
+ * Note that the above rule does not work for full outer joins; nor is it
+ * very interesting to consider cases where the generated equivalence clause
+ * would involve relations outside the outer join, since such clauses couldn't
+ * be pushed into the inner side's scan anyway. So the restriction to
+ * outervar = pseudoconstant is not really giving up anything.
+ *
+ * For full-join cases, we can only do something useful if it's a FULL JOIN
+ * USING and a merged column has an equivalence MERGEDVAR = CONSTANT.
+ * By the time it gets here, the merged column will look like
+ * COALESCE(LEFTVAR, RIGHTVAR)
+ * and we will have a full-join clause LEFTVAR = RIGHTVAR that we can match
+ * the COALESCE expression to. In this situation we can push LEFTVAR = CONSTANT
+ * and RIGHTVAR = CONSTANT into the input relations, since any rows not
+ * meeting these conditions cannot contribute to the join result.
+ *
+ * Again, there isn't any traction to be gained by trying to deal with
+ * clauses comparing a mergedvar to a non-pseudoconstant. So we can make
+ * use of the EquivalenceClasses to search for matching variables that were
+ * equivalenced to constants. The interesting outer-join clauses were
+ * accumulated for us by distribute_qual_to_rels.
+ *
+ * When we find one of these cases, we implement the changes we want by
+ * generating a new equivalence clause INNERVAR = CONSTANT (or LEFTVAR, etc)
+ * and pushing it into the EquivalenceClass structures. This is because we
+ * may already know that INNERVAR is equivalenced to some other var(s), and
+ * we'd like the constant to propagate to them too. Note that it would be
+ * unsafe to merge any existing EC for INNERVAR with the OUTERVAR's EC ---
+ * that could result in propagating constant restrictions from
+ * INNERVAR to OUTERVAR, which would be very wrong.
+ *
+ * It's possible that the INNERVAR is also an OUTERVAR for some other
+ * outer-join clause, in which case the process can be repeated. So we repeat
+ * looping over the lists of clauses until no further deductions can be made.
+ * Whenever we do make a deduction, we remove the generating clause from the
+ * lists, since we don't want to make the same deduction twice.
+ *
+ * If we don't find any match for a set-aside outer join clause, we must
+ * throw it back into the regular joinclause processing by passing it to
+ * distribute_restrictinfo_to_rels(). If we do generate a derived clause,
+ * however, the outer-join clause is redundant. We still throw it back,
+ * because otherwise the join will be seen as a clauseless join and avoided
+ * during join order searching; but we mark it as redundant to keep from
+ * messing up the joinrel's size estimate. (This behavior means that the
+ * API for this routine is uselessly complex: we could have just put all
+ * the clauses into the regular processing initially. We keep it because
+ * someday we might want to do something else, such as inserting "dummy"
+ * joinclauses instead of real ones.)
+ *
+ * Outer join clauses that are marked outerjoin_delayed are special: this
+ * condition means that one or both VARs might go to null due to a lower
+ * outer join. We can still push a constant through the clause, but only
+ * if its operator is strict; and we *have to* throw the clause back into
+ * regular joinclause processing. By keeping the strict join clause,
+ * we ensure that any null-extended rows that are mistakenly generated due
+ * to suppressing rows not matching the constant will be rejected at the
+ * upper outer join. (This doesn't work for full-join clauses.)
+ */
+void
+reconsider_outer_join_clauses(PlannerInfo *root)
+{
+ bool found;
+ ListCell *cell;
+
+ /* Outer loop repeats until we find no more deductions */
+ do
+ {
+ found = false;
+
+ /* Process the LEFT JOIN clauses */
+ foreach(cell, root->left_join_clauses)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
+
+ if (reconsider_outer_join_clause(root, rinfo, true))
+ {
+ found = true;
+ /* remove it from the list */
+ root->left_join_clauses =
+ foreach_delete_current(root->left_join_clauses, cell);
+ /* we throw it back anyway (see notes above) */
+ /* but the thrown-back clause has no extra selectivity */
+ rinfo->norm_selec = 2.0;
+ rinfo->outer_selec = 1.0;
+ distribute_restrictinfo_to_rels(root, rinfo);
+ }
+ }
+
+ /* Process the RIGHT JOIN clauses */
+ foreach(cell, root->right_join_clauses)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
+
+ if (reconsider_outer_join_clause(root, rinfo, false))
+ {
+ found = true;
+ /* remove it from the list */
+ root->right_join_clauses =
+ foreach_delete_current(root->right_join_clauses, cell);
+ /* we throw it back anyway (see notes above) */
+ /* but the thrown-back clause has no extra selectivity */
+ rinfo->norm_selec = 2.0;
+ rinfo->outer_selec = 1.0;
+ distribute_restrictinfo_to_rels(root, rinfo);
+ }
+ }
+
+ /* Process the FULL JOIN clauses */
+ foreach(cell, root->full_join_clauses)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
+
+ if (reconsider_full_join_clause(root, rinfo))
+ {
+ found = true;
+ /* remove it from the list */
+ root->full_join_clauses =
+ foreach_delete_current(root->full_join_clauses, cell);
+ /* we throw it back anyway (see notes above) */
+ /* but the thrown-back clause has no extra selectivity */
+ rinfo->norm_selec = 2.0;
+ rinfo->outer_selec = 1.0;
+ distribute_restrictinfo_to_rels(root, rinfo);
+ }
+ }
+ } while (found);
+
+ /* Now, any remaining clauses have to be thrown back */
+ foreach(cell, root->left_join_clauses)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
+
+ distribute_restrictinfo_to_rels(root, rinfo);
+ }
+ foreach(cell, root->right_join_clauses)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
+
+ distribute_restrictinfo_to_rels(root, rinfo);
+ }
+ foreach(cell, root->full_join_clauses)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
+
+ distribute_restrictinfo_to_rels(root, rinfo);
+ }
+}
+
+/*
+ * reconsider_outer_join_clauses for a single LEFT/RIGHT JOIN clause
+ *
+ * Returns true if we were able to propagate a constant through the clause.
+ */
+static bool
+reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo,
+ bool outer_on_left)
+{
+ Expr *outervar,
+ *innervar;
+ Oid opno,
+ collation,
+ left_type,
+ right_type,
+ inner_datatype;
+ Relids inner_relids,
+ inner_nullable_relids;
+ ListCell *lc1;
+
+ Assert(is_opclause(rinfo->clause));
+ opno = ((OpExpr *) rinfo->clause)->opno;
+ collation = ((OpExpr *) rinfo->clause)->inputcollid;
+
+ /* If clause is outerjoin_delayed, operator must be strict */
+ if (rinfo->outerjoin_delayed && !op_strict(opno))
+ return false;
+
+ /* Extract needed info from the clause */
+ op_input_types(opno, &left_type, &right_type);
+ if (outer_on_left)
+ {
+ outervar = (Expr *) get_leftop(rinfo->clause);
+ innervar = (Expr *) get_rightop(rinfo->clause);
+ inner_datatype = right_type;
+ inner_relids = rinfo->right_relids;
+ }
+ else
+ {
+ outervar = (Expr *) get_rightop(rinfo->clause);
+ innervar = (Expr *) get_leftop(rinfo->clause);
+ inner_datatype = left_type;
+ inner_relids = rinfo->left_relids;
+ }
+ inner_nullable_relids = bms_intersect(inner_relids,
+ rinfo->nullable_relids);
+
+ /* Scan EquivalenceClasses for a match to outervar */
+ foreach(lc1, root->eq_classes)
+ {
+ EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
+ bool match;
+ ListCell *lc2;
+
+ /* Ignore EC unless it contains pseudoconstants */
+ if (!cur_ec->ec_has_const)
+ continue;
+ /* Never match to a volatile EC */
+ if (cur_ec->ec_has_volatile)
+ continue;
+ /* It has to match the outer-join clause as to semantics, too */
+ if (collation != cur_ec->ec_collation)
+ continue;
+ if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
+ continue;
+ /* Does it contain a match to outervar? */
+ match = false;
+ foreach(lc2, cur_ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
+
+ Assert(!cur_em->em_is_child); /* no children yet */
+ if (equal(outervar, cur_em->em_expr))
+ {
+ match = true;
+ break;
+ }
+ }
+ if (!match)
+ continue; /* no match, so ignore this EC */
+
+ /*
+ * Yes it does! Try to generate a clause INNERVAR = CONSTANT for each
+ * CONSTANT in the EC. Note that we must succeed with at least one
+ * constant before we can decide to throw away the outer-join clause.
+ */
+ match = false;
+ foreach(lc2, cur_ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
+ Oid eq_op;
+ RestrictInfo *newrinfo;
+
+ if (!cur_em->em_is_const)
+ continue; /* ignore non-const members */
+ eq_op = select_equality_operator(cur_ec,
+ inner_datatype,
+ cur_em->em_datatype);
+ if (!OidIsValid(eq_op))
+ continue; /* can't generate equality */
+ newrinfo = build_implied_join_equality(root,
+ eq_op,
+ cur_ec->ec_collation,
+ innervar,
+ cur_em->em_expr,
+ bms_copy(inner_relids),
+ bms_copy(inner_nullable_relids),
+ cur_ec->ec_min_security);
+ if (process_equivalence(root, &newrinfo, true))
+ match = true;
+ }
+
+ /*
+ * If we were able to equate INNERVAR to any constant, report success.
+ * Otherwise, fall out of the search loop, since we know the OUTERVAR
+ * appears in at most one EC.
+ */
+ if (match)
+ return true;
+ else
+ break;
+ }
+
+ return false; /* failed to make any deduction */
+}
+
+/*
+ * reconsider_outer_join_clauses for a single FULL JOIN clause
+ *
+ * Returns true if we were able to propagate a constant through the clause.
+ */
+static bool
+reconsider_full_join_clause(PlannerInfo *root, RestrictInfo *rinfo)
+{
+ Expr *leftvar;
+ Expr *rightvar;
+ Oid opno,
+ collation,
+ left_type,
+ right_type;
+ Relids left_relids,
+ right_relids,
+ left_nullable_relids,
+ right_nullable_relids;
+ ListCell *lc1;
+
+ /* Can't use an outerjoin_delayed clause here */
+ if (rinfo->outerjoin_delayed)
+ return false;
+
+ /* Extract needed info from the clause */
+ Assert(is_opclause(rinfo->clause));
+ opno = ((OpExpr *) rinfo->clause)->opno;
+ collation = ((OpExpr *) rinfo->clause)->inputcollid;
+ op_input_types(opno, &left_type, &right_type);
+ leftvar = (Expr *) get_leftop(rinfo->clause);
+ rightvar = (Expr *) get_rightop(rinfo->clause);
+ left_relids = rinfo->left_relids;
+ right_relids = rinfo->right_relids;
+ left_nullable_relids = bms_intersect(left_relids,
+ rinfo->nullable_relids);
+ right_nullable_relids = bms_intersect(right_relids,
+ rinfo->nullable_relids);
+
+ foreach(lc1, root->eq_classes)
+ {
+ EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
+ EquivalenceMember *coal_em = NULL;
+ bool match;
+ bool matchleft;
+ bool matchright;
+ ListCell *lc2;
+ int coal_idx = -1;
+
+ /* Ignore EC unless it contains pseudoconstants */
+ if (!cur_ec->ec_has_const)
+ continue;
+ /* Never match to a volatile EC */
+ if (cur_ec->ec_has_volatile)
+ continue;
+ /* It has to match the outer-join clause as to semantics, too */
+ if (collation != cur_ec->ec_collation)
+ continue;
+ if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
+ continue;
+
+ /*
+ * Does it contain a COALESCE(leftvar, rightvar) construct?
+ *
+ * We can assume the COALESCE() inputs are in the same order as the
+ * join clause, since both were automatically generated in the cases
+ * we care about.
+ *
+ * XXX currently this may fail to match in cross-type cases because
+ * the COALESCE will contain typecast operations while the join clause
+ * may not (if there is a cross-type mergejoin operator available for
+ * the two column types). Is it OK to strip implicit coercions from
+ * the COALESCE arguments?
+ */
+ match = false;
+ foreach(lc2, cur_ec->ec_members)
+ {
+ coal_em = (EquivalenceMember *) lfirst(lc2);
+ Assert(!coal_em->em_is_child); /* no children yet */
+ if (IsA(coal_em->em_expr, CoalesceExpr))
+ {
+ CoalesceExpr *cexpr = (CoalesceExpr *) coal_em->em_expr;
+ Node *cfirst;
+ Node *csecond;
+
+ if (list_length(cexpr->args) != 2)
+ continue;
+ cfirst = (Node *) linitial(cexpr->args);
+ csecond = (Node *) lsecond(cexpr->args);
+
+ if (equal(leftvar, cfirst) && equal(rightvar, csecond))
+ {
+ coal_idx = foreach_current_index(lc2);
+ match = true;
+ break;
+ }
+ }
+ }
+ if (!match)
+ continue; /* no match, so ignore this EC */
+
+ /*
+ * Yes it does! Try to generate clauses LEFTVAR = CONSTANT and
+ * RIGHTVAR = CONSTANT for each CONSTANT in the EC. Note that we must
+ * succeed with at least one constant for each var before we can
+ * decide to throw away the outer-join clause.
+ */
+ matchleft = matchright = false;
+ foreach(lc2, cur_ec->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
+ Oid eq_op;
+ RestrictInfo *newrinfo;
+
+ if (!cur_em->em_is_const)
+ continue; /* ignore non-const members */
+ eq_op = select_equality_operator(cur_ec,
+ left_type,
+ cur_em->em_datatype);
+ if (OidIsValid(eq_op))
+ {
+ newrinfo = build_implied_join_equality(root,
+ eq_op,
+ cur_ec->ec_collation,
+ leftvar,
+ cur_em->em_expr,
+ bms_copy(left_relids),
+ bms_copy(left_nullable_relids),
+ cur_ec->ec_min_security);
+ if (process_equivalence(root, &newrinfo, true))
+ matchleft = true;
+ }
+ eq_op = select_equality_operator(cur_ec,
+ right_type,
+ cur_em->em_datatype);
+ if (OidIsValid(eq_op))
+ {
+ newrinfo = build_implied_join_equality(root,
+ eq_op,
+ cur_ec->ec_collation,
+ rightvar,
+ cur_em->em_expr,
+ bms_copy(right_relids),
+ bms_copy(right_nullable_relids),
+ cur_ec->ec_min_security);
+ if (process_equivalence(root, &newrinfo, true))
+ matchright = true;
+ }
+ }
+
+ /*
+ * If we were able to equate both vars to constants, we're done, and
+ * we can throw away the full-join clause as redundant. Moreover, we
+ * can remove the COALESCE entry from the EC, since the added
+ * restrictions ensure it will always have the expected value. (We
+ * don't bother trying to update ec_relids or ec_sources.)
+ */
+ if (matchleft && matchright)
+ {
+ cur_ec->ec_members = list_delete_nth_cell(cur_ec->ec_members, coal_idx);
+ return true;
+ }
+
+ /*
+ * Otherwise, fall out of the search loop, since we know the COALESCE
+ * appears in at most one EC (XXX might stop being true if we allow
+ * stripping of coercions above?)
+ */
+ break;
+ }
+
+ return false; /* failed to make any deduction */
+}
+
+
+/*
+ * exprs_known_equal
+ * Detect whether two expressions are known equal due to equivalence
+ * relationships.
+ *
+ * Actually, this only shows that the expressions are equal according
+ * to some opfamily's notion of equality --- but we only use it for
+ * selectivity estimation, so a fuzzy idea of equality is OK.
+ *
+ * Note: does not bother to check for "equal(item1, item2)"; caller must
+ * check that case if it's possible to pass identical items.
+ */
+bool
+exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2)
+{
+ ListCell *lc1;
+
+ foreach(lc1, root->eq_classes)
+ {
+ EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
+ bool item1member = false;
+ bool item2member = false;
+ ListCell *lc2;
+
+ /* Never match to a volatile EC */
+ if (ec->ec_has_volatile)
+ continue;
+
+ foreach(lc2, ec->ec_members)
+ {
+ EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
+
+ if (em->em_is_child)
+ continue; /* ignore children here */
+ if (equal(item1, em->em_expr))
+ item1member = true;
+ else if (equal(item2, em->em_expr))
+ item2member = true;
+ /* Exit as soon as equality is proven */
+ if (item1member && item2member)
+ return true;
+ }
+ }
+ return false;
+}
+
+
+/*
+ * match_eclasses_to_foreign_key_col
+ * See whether a foreign key column match is proven by any eclass.
+ *
+ * If the referenced and referencing Vars of the fkey's colno'th column are
+ * known equal due to any eclass, return that eclass; otherwise return NULL.
+ * (In principle there might be more than one matching eclass if multiple
+ * collations are involved, but since collation doesn't matter for equality,
+ * we ignore that fine point here.) This is much like exprs_known_equal,
+ * except that we insist on the comparison operator matching the eclass, so
+ * that the result is definite not approximate.
+ *
+ * On success, we also set fkinfo->eclass[colno] to the matching eclass,
+ * and set fkinfo->fk_eclass_member[colno] to the eclass member for the
+ * referencing Var.
+ */
+EquivalenceClass *
+match_eclasses_to_foreign_key_col(PlannerInfo *root,
+ ForeignKeyOptInfo *fkinfo,
+ int colno)
+{
+ Index var1varno = fkinfo->con_relid;
+ AttrNumber var1attno = fkinfo->conkey[colno];
+ Index var2varno = fkinfo->ref_relid;
+ AttrNumber var2attno = fkinfo->confkey[colno];
+ Oid eqop = fkinfo->conpfeqop[colno];
+ RelOptInfo *rel1 = root->simple_rel_array[var1varno];
+ RelOptInfo *rel2 = root->simple_rel_array[var2varno];
+ List *opfamilies = NIL; /* compute only if needed */
+ Bitmapset *matching_ecs;
+ int i;
+
+ /* Consider only eclasses mentioning both relations */
+ Assert(root->ec_merging_done);
+ Assert(IS_SIMPLE_REL(rel1));
+ Assert(IS_SIMPLE_REL(rel2));
+ matching_ecs = bms_intersect(rel1->eclass_indexes,
+ rel2->eclass_indexes);
+
+ i = -1;
+ while ((i = bms_next_member(matching_ecs, i)) >= 0)
+ {
+ EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
+ i);
+ EquivalenceMember *item1_em = NULL;
+ EquivalenceMember *item2_em = NULL;
+ ListCell *lc2;
+
+ /* Never match to a volatile EC */
+ if (ec->ec_has_volatile)
+ continue;
+ /* Note: it seems okay to match to "broken" eclasses here */
+
+ foreach(lc2, ec->ec_members)
+ {
+ EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
+ Var *var;
+
+ if (em->em_is_child)
+ continue; /* ignore children here */
+
+ /* EM must be a Var, possibly with RelabelType */
+ var = (Var *) em->em_expr;
+ while (var && IsA(var, RelabelType))
+ var = (Var *) ((RelabelType *) var)->arg;
+ if (!(var && IsA(var, Var)))
+ continue;
+
+ /* Match? */
+ if (var->varno == var1varno && var->varattno == var1attno)
+ item1_em = em;
+ else if (var->varno == var2varno && var->varattno == var2attno)
+ item2_em = em;
+
+ /* Have we found both PK and FK column in this EC? */
+ if (item1_em && item2_em)
+ {
+ /*
+ * Succeed if eqop matches EC's opfamilies. We could test
+ * this before scanning the members, but it's probably cheaper
+ * to test for member matches first.
+ */
+ if (opfamilies == NIL) /* compute if we didn't already */
+ opfamilies = get_mergejoin_opfamilies(eqop);
+ if (equal(opfamilies, ec->ec_opfamilies))
+ {
+ fkinfo->eclass[colno] = ec;
+ fkinfo->fk_eclass_member[colno] = item2_em;
+ return ec;
+ }
+ /* Otherwise, done with this EC, move on to the next */
+ break;
+ }
+ }
+ }
+ return NULL;
+}
+
+/*
+ * find_derived_clause_for_ec_member
+ * Search for a previously-derived clause mentioning the given EM.
+ *
+ * The eclass should be an ec_has_const EC, of which the EM is a non-const
+ * member. This should ensure there is just one derived clause mentioning
+ * the EM (and equating it to a constant).
+ * Returns NULL if no such clause can be found.
+ */
+RestrictInfo *
+find_derived_clause_for_ec_member(EquivalenceClass *ec,
+ EquivalenceMember *em)
+{
+ ListCell *lc;
+
+ Assert(ec->ec_has_const);
+ Assert(!em->em_is_const);
+ foreach(lc, ec->ec_derives)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
+
+ /*
+ * generate_base_implied_equalities_const will have put non-const
+ * members on the left side of derived clauses.
+ */
+ if (rinfo->left_em == em)
+ return rinfo;
+ }
+ return NULL;
+}
+
+
+/*
+ * add_child_rel_equivalences
+ * Search for EC members that reference the root parent of child_rel, and
+ * add transformed members referencing the child_rel.
+ *
+ * Note that this function won't be called at all unless we have at least some
+ * reason to believe that the EC members it generates will be useful.
+ *
+ * parent_rel and child_rel could be derived from appinfo, but since the
+ * caller has already computed them, we might as well just pass them in.
+ *
+ * The passed-in AppendRelInfo is not used when the parent_rel is not a
+ * top-level baserel, since it shows the mapping from the parent_rel but
+ * we need to translate EC expressions that refer to the top-level parent.
+ * Using it is faster than using adjust_appendrel_attrs_multilevel(), though,
+ * so we prefer it when we can.
+ */
+void
+add_child_rel_equivalences(PlannerInfo *root,
+ AppendRelInfo *appinfo,
+ RelOptInfo *parent_rel,
+ RelOptInfo *child_rel)
+{
+ Relids top_parent_relids = child_rel->top_parent_relids;
+ Relids child_relids = child_rel->relids;
+ int i;
+
+ /*
+ * EC merging should be complete already, so we can use the parent rel's
+ * eclass_indexes to avoid searching all of root->eq_classes.
+ */
+ Assert(root->ec_merging_done);
+ Assert(IS_SIMPLE_REL(parent_rel));
+
+ i = -1;
+ while ((i = bms_next_member(parent_rel->eclass_indexes, i)) >= 0)
+ {
+ EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
+ int num_members;
+
+ /*
+ * If this EC contains a volatile expression, then generating child
+ * EMs would be downright dangerous, so skip it. We rely on a
+ * volatile EC having only one EM.
+ */
+ if (cur_ec->ec_has_volatile)
+ continue;
+
+ /* Sanity check eclass_indexes only contain ECs for parent_rel */
+ Assert(bms_is_subset(top_parent_relids, cur_ec->ec_relids));
+
+ /*
+ * We don't use foreach() here because there's no point in scanning
+ * newly-added child members, so we can stop after the last
+ * pre-existing EC member.
+ */
+ num_members = list_length(cur_ec->ec_members);
+ for (int pos = 0; pos < num_members; pos++)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
+
+ if (cur_em->em_is_const)
+ continue; /* ignore consts here */
+
+ /*
+ * We consider only original EC members here, not
+ * already-transformed child members. Otherwise, if some original
+ * member expression references more than one appendrel, we'd get
+ * an O(N^2) explosion of useless derived expressions for
+ * combinations of children. (But add_child_join_rel_equivalences
+ * may add targeted combinations for partitionwise-join purposes.)
+ */
+ if (cur_em->em_is_child)
+ continue; /* ignore children here */
+
+ /* Does this member reference child's topmost parent rel? */
+ if (bms_overlap(cur_em->em_relids, top_parent_relids))
+ {
+ /* Yes, generate transformed child version */
+ Expr *child_expr;
+ Relids new_relids;
+ Relids new_nullable_relids;
+
+ if (parent_rel->reloptkind == RELOPT_BASEREL)
+ {
+ /* Simple single-level transformation */
+ child_expr = (Expr *)
+ adjust_appendrel_attrs(root,
+ (Node *) cur_em->em_expr,
+ 1, &appinfo);
+ }
+ else
+ {
+ /* Must do multi-level transformation */
+ child_expr = (Expr *)
+ adjust_appendrel_attrs_multilevel(root,
+ (Node *) cur_em->em_expr,
+ child_relids,
+ top_parent_relids);
+ }
+
+ /*
+ * Transform em_relids to match. Note we do *not* do
+ * pull_varnos(child_expr) here, as for example the
+ * transformation might have substituted a constant, but we
+ * don't want the child member to be marked as constant.
+ */
+ new_relids = bms_difference(cur_em->em_relids,
+ top_parent_relids);
+ new_relids = bms_add_members(new_relids, child_relids);
+
+ /*
+ * And likewise for nullable_relids. Note this code assumes
+ * parent and child relids are singletons.
+ */
+ new_nullable_relids = cur_em->em_nullable_relids;
+ if (bms_overlap(new_nullable_relids, top_parent_relids))
+ {
+ new_nullable_relids = bms_difference(new_nullable_relids,
+ top_parent_relids);
+ new_nullable_relids = bms_add_members(new_nullable_relids,
+ child_relids);
+ }
+
+ (void) add_eq_member(cur_ec, child_expr,
+ new_relids, new_nullable_relids,
+ true, cur_em->em_datatype);
+
+ /* Record this EC index for the child rel */
+ child_rel->eclass_indexes = bms_add_member(child_rel->eclass_indexes, i);
+ }
+ }
+ }
+}
+
+/*
+ * add_child_join_rel_equivalences
+ * Like add_child_rel_equivalences(), but for joinrels
+ *
+ * Here we find the ECs relevant to the top parent joinrel and add transformed
+ * member expressions that refer to this child joinrel.
+ *
+ * Note that this function won't be called at all unless we have at least some
+ * reason to believe that the EC members it generates will be useful.
+ */
+void
+add_child_join_rel_equivalences(PlannerInfo *root,
+ int nappinfos, AppendRelInfo **appinfos,
+ RelOptInfo *parent_joinrel,
+ RelOptInfo *child_joinrel)
+{
+ Relids top_parent_relids = child_joinrel->top_parent_relids;
+ Relids child_relids = child_joinrel->relids;
+ Bitmapset *matching_ecs;
+ MemoryContext oldcontext;
+ int i;
+
+ Assert(IS_JOIN_REL(child_joinrel) && IS_JOIN_REL(parent_joinrel));
+
+ /* We need consider only ECs that mention the parent joinrel */
+ matching_ecs = get_eclass_indexes_for_relids(root, top_parent_relids);
+
+ /*
+ * If we're being called during GEQO join planning, we still have to
+ * create any new EC members in the main planner context, to avoid having
+ * a corrupt EC data structure after the GEQO context is reset. This is
+ * problematic since we'll leak memory across repeated GEQO cycles. For
+ * now, though, bloat is better than crash. If it becomes a real issue
+ * we'll have to do something to avoid generating duplicate EC members.
+ */
+ oldcontext = MemoryContextSwitchTo(root->planner_cxt);
+
+ i = -1;
+ while ((i = bms_next_member(matching_ecs, i)) >= 0)
+ {
+ EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
+ int num_members;
+
+ /*
+ * If this EC contains a volatile expression, then generating child
+ * EMs would be downright dangerous, so skip it. We rely on a
+ * volatile EC having only one EM.
+ */
+ if (cur_ec->ec_has_volatile)
+ continue;
+
+ /* Sanity check on get_eclass_indexes_for_relids result */
+ Assert(bms_overlap(top_parent_relids, cur_ec->ec_relids));
+
+ /*
+ * We don't use foreach() here because there's no point in scanning
+ * newly-added child members, so we can stop after the last
+ * pre-existing EC member.
+ */
+ num_members = list_length(cur_ec->ec_members);
+ for (int pos = 0; pos < num_members; pos++)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
+
+ if (cur_em->em_is_const)
+ continue; /* ignore consts here */
+
+ /*
+ * We consider only original EC members here, not
+ * already-transformed child members.
+ */
+ if (cur_em->em_is_child)
+ continue; /* ignore children here */
+
+ /*
+ * We may ignore expressions that reference a single baserel,
+ * because add_child_rel_equivalences should have handled them.
+ */
+ if (bms_membership(cur_em->em_relids) != BMS_MULTIPLE)
+ continue;
+
+ /* Does this member reference child's topmost parent rel? */
+ if (bms_overlap(cur_em->em_relids, top_parent_relids))
+ {
+ /* Yes, generate transformed child version */
+ Expr *child_expr;
+ Relids new_relids;
+ Relids new_nullable_relids;
+
+ if (parent_joinrel->reloptkind == RELOPT_JOINREL)
+ {
+ /* Simple single-level transformation */
+ child_expr = (Expr *)
+ adjust_appendrel_attrs(root,
+ (Node *) cur_em->em_expr,
+ nappinfos, appinfos);
+ }
+ else
+ {
+ /* Must do multi-level transformation */
+ Assert(parent_joinrel->reloptkind == RELOPT_OTHER_JOINREL);
+ child_expr = (Expr *)
+ adjust_appendrel_attrs_multilevel(root,
+ (Node *) cur_em->em_expr,
+ child_relids,
+ top_parent_relids);
+ }
+
+ /*
+ * Transform em_relids to match. Note we do *not* do
+ * pull_varnos(child_expr) here, as for example the
+ * transformation might have substituted a constant, but we
+ * don't want the child member to be marked as constant.
+ */
+ new_relids = bms_difference(cur_em->em_relids,
+ top_parent_relids);
+ new_relids = bms_add_members(new_relids, child_relids);
+
+ /*
+ * For nullable_relids, we must selectively replace parent
+ * nullable relids with child ones.
+ */
+ new_nullable_relids = cur_em->em_nullable_relids;
+ if (bms_overlap(new_nullable_relids, top_parent_relids))
+ new_nullable_relids =
+ adjust_child_relids_multilevel(root,
+ new_nullable_relids,
+ child_relids,
+ top_parent_relids);
+
+ (void) add_eq_member(cur_ec, child_expr,
+ new_relids, new_nullable_relids,
+ true, cur_em->em_datatype);
+ }
+ }
+ }
+
+ MemoryContextSwitchTo(oldcontext);
+}
+
+
+/*
+ * generate_implied_equalities_for_column
+ * Create EC-derived joinclauses usable with a specific column.
+ *
+ * This is used by indxpath.c to extract potentially indexable joinclauses
+ * from ECs, and can be used by foreign data wrappers for similar purposes.
+ * We assume that only expressions in Vars of a single table are of interest,
+ * but the caller provides a callback function to identify exactly which
+ * such expressions it would like to know about.
+ *
+ * We assume that any given table/index column could appear in only one EC.
+ * (This should be true in all but the most pathological cases, and if it
+ * isn't, we stop on the first match anyway.) Therefore, what we return
+ * is a redundant list of clauses equating the table/index column to each of
+ * the other-relation values it is known to be equal to. Any one of
+ * these clauses can be used to create a parameterized path, and there
+ * is no value in using more than one. (But it *is* worthwhile to create
+ * a separate parameterized path for each one, since that leads to different
+ * join orders.)
+ *
+ * The caller can pass a Relids set of rels we aren't interested in joining
+ * to, so as to save the work of creating useless clauses.
+ */
+List *
+generate_implied_equalities_for_column(PlannerInfo *root,
+ RelOptInfo *rel,
+ ec_matches_callback_type callback,
+ void *callback_arg,
+ Relids prohibited_rels)
+{
+ List *result = NIL;
+ bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
+ Relids parent_relids;
+ int i;
+
+ /* Should be OK to rely on eclass_indexes */
+ Assert(root->ec_merging_done);
+
+ /* Indexes are available only on base or "other" member relations. */
+ Assert(IS_SIMPLE_REL(rel));
+
+ /* If it's a child rel, we'll need to know what its parent(s) are */
+ if (is_child_rel)
+ parent_relids = find_childrel_parents(root, rel);
+ else
+ parent_relids = NULL; /* not used, but keep compiler quiet */
+
+ i = -1;
+ while ((i = bms_next_member(rel->eclass_indexes, i)) >= 0)
+ {
+ EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
+ EquivalenceMember *cur_em;
+ ListCell *lc2;
+
+ /* Sanity check eclass_indexes only contain ECs for rel */
+ Assert(is_child_rel || bms_is_subset(rel->relids, cur_ec->ec_relids));
+
+ /*
+ * Won't generate joinclauses if const or single-member (the latter
+ * test covers the volatile case too)
+ */
+ if (cur_ec->ec_has_const || list_length(cur_ec->ec_members) <= 1)
+ continue;
+
+ /*
+ * Scan members, looking for a match to the target column. Note that
+ * child EC members are considered, but only when they belong to the
+ * target relation. (Unlike regular members, the same expression
+ * could be a child member of more than one EC. Therefore, it's
+ * potentially order-dependent which EC a child relation's target
+ * column gets matched to. This is annoying but it only happens in
+ * corner cases, so for now we live with just reporting the first
+ * match. See also get_eclass_for_sort_expr.)
+ */
+ cur_em = NULL;
+ foreach(lc2, cur_ec->ec_members)
+ {
+ cur_em = (EquivalenceMember *) lfirst(lc2);
+ if (bms_equal(cur_em->em_relids, rel->relids) &&
+ callback(root, rel, cur_ec, cur_em, callback_arg))
+ break;
+ cur_em = NULL;
+ }
+
+ if (!cur_em)
+ continue;
+
+ /*
+ * Found our match. Scan the other EC members and attempt to generate
+ * joinclauses.
+ */
+ foreach(lc2, cur_ec->ec_members)
+ {
+ EquivalenceMember *other_em = (EquivalenceMember *) lfirst(lc2);
+ Oid eq_op;
+ RestrictInfo *rinfo;
+
+ if (other_em->em_is_child)
+ continue; /* ignore children here */
+
+ /* Make sure it'll be a join to a different rel */
+ if (other_em == cur_em ||
+ bms_overlap(other_em->em_relids, rel->relids))
+ continue;
+
+ /* Forget it if caller doesn't want joins to this rel */
+ if (bms_overlap(other_em->em_relids, prohibited_rels))
+ continue;
+
+ /*
+ * Also, if this is a child rel, avoid generating a useless join
+ * to its parent rel(s).
+ */
+ if (is_child_rel &&
+ bms_overlap(parent_relids, other_em->em_relids))
+ continue;
+
+ eq_op = select_equality_operator(cur_ec,
+ cur_em->em_datatype,
+ other_em->em_datatype);
+ if (!OidIsValid(eq_op))
+ continue;
+
+ /* set parent_ec to mark as redundant with other joinclauses */
+ rinfo = create_join_clause(root, cur_ec, eq_op,
+ cur_em, other_em,
+ cur_ec);
+
+ result = lappend(result, rinfo);
+ }
+
+ /*
+ * If somehow we failed to create any join clauses, we might as well
+ * keep scanning the ECs for another match. But if we did make any,
+ * we're done, because we don't want to return non-redundant clauses.
+ */
+ if (result)
+ break;
+ }
+
+ return result;
+}
+
+/*
+ * have_relevant_eclass_joinclause
+ * Detect whether there is an EquivalenceClass that could produce
+ * a joinclause involving the two given relations.
+ *
+ * This is essentially a very cut-down version of
+ * generate_join_implied_equalities(). Note it's OK to occasionally say "yes"
+ * incorrectly. Hence we don't bother with details like whether the lack of a
+ * cross-type operator might prevent the clause from actually being generated.
+ */
+bool
+have_relevant_eclass_joinclause(PlannerInfo *root,
+ RelOptInfo *rel1, RelOptInfo *rel2)
+{
+ Bitmapset *matching_ecs;
+ int i;
+
+ /* Examine only eclasses mentioning both rel1 and rel2 */
+ matching_ecs = get_common_eclass_indexes(root, rel1->relids,
+ rel2->relids);
+
+ i = -1;
+ while ((i = bms_next_member(matching_ecs, i)) >= 0)
+ {
+ EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
+ i);
+
+ /*
+ * Sanity check that get_common_eclass_indexes gave only ECs
+ * containing both rels.
+ */
+ Assert(bms_overlap(rel1->relids, ec->ec_relids));
+ Assert(bms_overlap(rel2->relids, ec->ec_relids));
+
+ /*
+ * Won't generate joinclauses if single-member (this test covers the
+ * volatile case too)
+ */
+ if (list_length(ec->ec_members) <= 1)
+ continue;
+
+ /*
+ * We do not need to examine the individual members of the EC, because
+ * all that we care about is whether each rel overlaps the relids of
+ * at least one member, and get_common_eclass_indexes() and the single
+ * member check above are sufficient to prove that. (As with
+ * have_relevant_joinclause(), it is not necessary that the EC be able
+ * to form a joinclause relating exactly the two given rels, only that
+ * it be able to form a joinclause mentioning both, and this will
+ * surely be true if both of them overlap ec_relids.)
+ *
+ * Note we don't test ec_broken; if we did, we'd need a separate code
+ * path to look through ec_sources. Checking the membership anyway is
+ * OK as a possibly-overoptimistic heuristic.
+ *
+ * We don't test ec_has_const either, even though a const eclass won't
+ * generate real join clauses. This is because if we had "WHERE a.x =
+ * b.y and a.x = 42", it is worth considering a join between a and b,
+ * since the join result is likely to be small even though it'll end
+ * up being an unqualified nestloop.
+ */
+
+ return true;
+ }
+
+ return false;
+}
+
+
+/*
+ * has_relevant_eclass_joinclause
+ * Detect whether there is an EquivalenceClass that could produce
+ * a joinclause involving the given relation and anything else.
+ *
+ * This is the same as have_relevant_eclass_joinclause with the other rel
+ * implicitly defined as "everything else in the query".
+ */
+bool
+has_relevant_eclass_joinclause(PlannerInfo *root, RelOptInfo *rel1)
+{
+ Bitmapset *matched_ecs;
+ int i;
+
+ /* Examine only eclasses mentioning rel1 */
+ matched_ecs = get_eclass_indexes_for_relids(root, rel1->relids);
+
+ i = -1;
+ while ((i = bms_next_member(matched_ecs, i)) >= 0)
+ {
+ EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
+ i);
+
+ /*
+ * Won't generate joinclauses if single-member (this test covers the
+ * volatile case too)
+ */
+ if (list_length(ec->ec_members) <= 1)
+ continue;
+
+ /*
+ * Per the comment in have_relevant_eclass_joinclause, it's sufficient
+ * to find an EC that mentions both this rel and some other rel.
+ */
+ if (!bms_is_subset(ec->ec_relids, rel1->relids))
+ return true;
+ }
+
+ return false;
+}
+
+
+/*
+ * eclass_useful_for_merging
+ * Detect whether the EC could produce any mergejoinable join clauses
+ * against the specified relation.
+ *
+ * This is just a heuristic test and doesn't have to be exact; it's better
+ * to say "yes" incorrectly than "no". Hence we don't bother with details
+ * like whether the lack of a cross-type operator might prevent the clause
+ * from actually being generated.
+ */
+bool
+eclass_useful_for_merging(PlannerInfo *root,
+ EquivalenceClass *eclass,
+ RelOptInfo *rel)
+{
+ Relids relids;
+ ListCell *lc;
+
+ Assert(!eclass->ec_merged);
+
+ /*
+ * Won't generate joinclauses if const or single-member (the latter test
+ * covers the volatile case too)
+ */
+ if (eclass->ec_has_const || list_length(eclass->ec_members) <= 1)
+ return false;
+
+ /*
+ * Note we don't test ec_broken; if we did, we'd need a separate code path
+ * to look through ec_sources. Checking the members anyway is OK as a
+ * possibly-overoptimistic heuristic.
+ */
+
+ /* If specified rel is a child, we must consider the topmost parent rel */
+ if (IS_OTHER_REL(rel))
+ {
+ Assert(!bms_is_empty(rel->top_parent_relids));
+ relids = rel->top_parent_relids;
+ }
+ else
+ relids = rel->relids;
+
+ /* If rel already includes all members of eclass, no point in searching */
+ if (bms_is_subset(eclass->ec_relids, relids))
+ return false;
+
+ /* To join, we need a member not in the given rel */
+ foreach(lc, eclass->ec_members)
+ {
+ EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
+
+ if (cur_em->em_is_child)
+ continue; /* ignore children here */
+
+ if (!bms_overlap(cur_em->em_relids, relids))
+ return true;
+ }
+
+ return false;
+}
+
+
+/*
+ * is_redundant_derived_clause
+ * Test whether rinfo is derived from same EC as any clause in clauselist;
+ * if so, it can be presumed to represent a condition that's redundant
+ * with that member of the list.
+ */
+bool
+is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist)
+{
+ EquivalenceClass *parent_ec = rinfo->parent_ec;
+ ListCell *lc;
+
+ /* Fail if it's not a potentially-redundant clause from some EC */
+ if (parent_ec == NULL)
+ return false;
+
+ foreach(lc, clauselist)
+ {
+ RestrictInfo *otherrinfo = (RestrictInfo *) lfirst(lc);
+
+ if (otherrinfo->parent_ec == parent_ec)
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * is_redundant_with_indexclauses
+ * Test whether rinfo is redundant with any clause in the IndexClause
+ * list. Here, for convenience, we test both simple identity and
+ * whether it is derived from the same EC as any member of the list.
+ */
+bool
+is_redundant_with_indexclauses(RestrictInfo *rinfo, List *indexclauses)
+{
+ EquivalenceClass *parent_ec = rinfo->parent_ec;
+ ListCell *lc;
+
+ foreach(lc, indexclauses)
+ {
+ IndexClause *iclause = lfirst_node(IndexClause, lc);
+ RestrictInfo *otherrinfo = iclause->rinfo;
+
+ /* If indexclause is lossy, it won't enforce the condition exactly */
+ if (iclause->lossy)
+ continue;
+
+ /* Match if it's same clause (pointer equality should be enough) */
+ if (rinfo == otherrinfo)
+ return true;
+ /* Match if derived from same EC */
+ if (parent_ec && otherrinfo->parent_ec == parent_ec)
+ return true;
+
+ /*
+ * No need to look at the derived clauses in iclause->indexquals; they
+ * couldn't match if the parent clause didn't.
+ */
+ }
+
+ return false;
+}
+
+/*
+ * get_eclass_indexes_for_relids
+ * Build and return a Bitmapset containing the indexes into root's
+ * eq_classes list for all eclasses that mention any of these relids
+ */
+static Bitmapset *
+get_eclass_indexes_for_relids(PlannerInfo *root, Relids relids)
+{
+ Bitmapset *ec_indexes = NULL;
+ int i = -1;
+
+ /* Should be OK to rely on eclass_indexes */
+ Assert(root->ec_merging_done);
+
+ while ((i = bms_next_member(relids, i)) > 0)
+ {
+ RelOptInfo *rel = root->simple_rel_array[i];
+
+ ec_indexes = bms_add_members(ec_indexes, rel->eclass_indexes);
+ }
+ return ec_indexes;
+}
+
+/*
+ * get_common_eclass_indexes
+ * Build and return a Bitmapset containing the indexes into root's
+ * eq_classes list for all eclasses that mention rels in both
+ * relids1 and relids2.
+ */
+static Bitmapset *
+get_common_eclass_indexes(PlannerInfo *root, Relids relids1, Relids relids2)
+{
+ Bitmapset *rel1ecs;
+ Bitmapset *rel2ecs;
+ int relid;
+
+ rel1ecs = get_eclass_indexes_for_relids(root, relids1);
+
+ /*
+ * We can get away with just using the relation's eclass_indexes directly
+ * when relids2 is a singleton set.
+ */
+ if (bms_get_singleton_member(relids2, &relid))
+ rel2ecs = root->simple_rel_array[relid]->eclass_indexes;
+ else
+ rel2ecs = get_eclass_indexes_for_relids(root, relids2);
+
+ /* Calculate and return the common EC indexes, recycling the left input. */
+ return bms_int_members(rel1ecs, rel2ecs);
+}