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ORDER BY <constant> as redundant. One is that this means query_planner() has to canonicalize pathkeys even when the query jointree is empty; the canonicalization was always a no-op in such cases before, but no more. Also, we have to guard against thinking that a set-returning function is "constant" for this purpose. Add a couple of regression tests for these evidently under-tested cases. Per report from Greg Stark and subsequent experimentation.
1780 lines
54 KiB
C
1780 lines
54 KiB
C
/*-------------------------------------------------------------------------
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*
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* equivclass.c
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* Routines for managing EquivalenceClasses
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*
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* See src/backend/optimizer/README for discussion of EquivalenceClasses.
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*
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*
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* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/path/equivclass.c,v 1.3 2007/07/07 20:46:45 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/skey.h"
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#include "optimizer/clauses.h"
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#include "optimizer/cost.h"
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#include "optimizer/paths.h"
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#include "optimizer/planmain.h"
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#include "optimizer/prep.h"
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#include "optimizer/var.h"
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#include "utils/lsyscache.h"
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static EquivalenceMember *add_eq_member(EquivalenceClass *ec,
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Expr *expr, Relids relids,
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bool is_child, Oid datatype);
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static void generate_base_implied_equalities_const(PlannerInfo *root,
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EquivalenceClass *ec);
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static void generate_base_implied_equalities_no_const(PlannerInfo *root,
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EquivalenceClass *ec);
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static void generate_base_implied_equalities_broken(PlannerInfo *root,
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EquivalenceClass *ec);
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static List *generate_join_implied_equalities_normal(PlannerInfo *root,
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EquivalenceClass *ec,
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RelOptInfo *joinrel,
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RelOptInfo *outer_rel,
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RelOptInfo *inner_rel);
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static List *generate_join_implied_equalities_broken(PlannerInfo *root,
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EquivalenceClass *ec,
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RelOptInfo *joinrel,
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RelOptInfo *outer_rel,
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RelOptInfo *inner_rel);
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static Oid select_equality_operator(EquivalenceClass *ec,
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Oid lefttype, Oid righttype);
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static RestrictInfo *create_join_clause(PlannerInfo *root,
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EquivalenceClass *ec, Oid opno,
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EquivalenceMember *leftem,
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EquivalenceMember *rightem,
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EquivalenceClass *parent_ec);
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static void reconsider_outer_join_clause(PlannerInfo *root,
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RestrictInfo *rinfo,
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bool outer_on_left);
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static void reconsider_full_join_clause(PlannerInfo *root,
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RestrictInfo *rinfo);
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/*
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* process_equivalence
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* The given clause has a mergejoinable operator and can be applied without
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* any delay by an outer join, so its two sides can be considered equal
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* anywhere they are both computable; moreover that equality can be
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* extended transitively. Record this knowledge in the EquivalenceClass
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* data structure. Returns TRUE if successful, FALSE if not (in which
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* case caller should treat the clause as ordinary, not an equivalence).
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*
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* If below_outer_join is true, then the clause was found below the nullable
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* side of an outer join, so its sides might validly be both NULL rather than
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* strictly equal. We can still deduce equalities in such cases, but we take
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* care to mark an EquivalenceClass if it came from any such clauses. Also,
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* we have to check that both sides are either pseudo-constants or strict
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* functions of Vars, else they might not both go to NULL above the outer
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* join. (This is the reason why we need a failure return. It's more
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* convenient to check this case here than at the call sites...)
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*
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* Note: constructing merged EquivalenceClasses is a standard UNION-FIND
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* problem, for which there exist better data structures than simple lists.
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* If this code ever proves to be a bottleneck then it could be sped up ---
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* but for now, simple is beautiful.
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*
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* Note: this is only called during planner startup, not during GEQO
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* exploration, so we need not worry about whether we're in the right
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* memory context.
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*/
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bool
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process_equivalence(PlannerInfo *root, RestrictInfo *restrictinfo,
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bool below_outer_join)
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{
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Expr *clause = restrictinfo->clause;
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Oid opno,
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item1_type,
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item2_type;
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Expr *item1;
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Expr *item2;
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Relids item1_relids,
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item2_relids;
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List *opfamilies;
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EquivalenceClass *ec1,
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*ec2;
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EquivalenceMember *em1,
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*em2;
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ListCell *lc1;
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/* Extract info from given clause */
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Assert(is_opclause(clause));
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opno = ((OpExpr *) clause)->opno;
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item1 = (Expr *) get_leftop(clause);
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item2 = (Expr *) get_rightop(clause);
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item1_relids = restrictinfo->left_relids;
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item2_relids = restrictinfo->right_relids;
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/*
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* If below outer join, check for strictness, else reject.
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*/
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if (below_outer_join)
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{
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if (!bms_is_empty(item1_relids) &&
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contain_nonstrict_functions((Node *) item1))
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return false; /* LHS is non-strict but not constant */
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if (!bms_is_empty(item2_relids) &&
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contain_nonstrict_functions((Node *) item2))
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return false; /* RHS is non-strict but not constant */
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}
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/*
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* We use the declared input types of the operator, not exprType() of
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* the inputs, as the nominal datatypes for opfamily lookup. This
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* presumes that btree operators are always registered with amoplefttype
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* and amoprighttype equal to their declared input types. We will need
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* this info anyway to build EquivalenceMember nodes, and by extracting
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* it now we can use type comparisons to short-circuit some equal() tests.
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*/
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op_input_types(opno, &item1_type, &item2_type);
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opfamilies = restrictinfo->mergeopfamilies;
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/*
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* Sweep through the existing EquivalenceClasses looking for matches
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* to item1 and item2. These are the possible outcomes:
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*
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* 1. We find both in the same EC. The equivalence is already known,
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* so there's nothing to do.
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*
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* 2. We find both in different ECs. Merge the two ECs together.
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*
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* 3. We find just one. Add the other to its EC.
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*
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* 4. We find neither. Make a new, two-entry EC.
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*
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* Note: since all ECs are built through this process, it's impossible
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* that we'd match an item in more than one existing EC. It is possible
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* to match more than once within an EC, if someone fed us something silly
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* like "WHERE X=X". (However, we can't simply discard such clauses,
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* since they should fail when X is null; so we will build a 2-member
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* EC to ensure the correct restriction clause gets generated. Hence
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* there is no shortcut here for item1 and item2 equal.)
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*/
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ec1 = ec2 = NULL;
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em1 = em2 = NULL;
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foreach(lc1, root->eq_classes)
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{
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EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
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ListCell *lc2;
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/* Never match to a volatile EC */
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if (cur_ec->ec_has_volatile)
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continue;
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/*
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* A "match" requires matching sets of btree opfamilies. Use of
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* equal() for this test has implications discussed in the comments
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* for get_mergejoin_opfamilies().
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*/
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if (!equal(opfamilies, cur_ec->ec_opfamilies))
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continue;
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foreach(lc2, cur_ec->ec_members)
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{
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EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
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Assert(!cur_em->em_is_child); /* no children yet */
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/*
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* If below an outer join, don't match constants: they're not
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* as constant as they look.
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*/
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if ((below_outer_join || cur_ec->ec_below_outer_join) &&
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cur_em->em_is_const)
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continue;
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if (!ec1 &&
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item1_type == cur_em->em_datatype &&
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equal(item1, cur_em->em_expr))
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{
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ec1 = cur_ec;
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em1 = cur_em;
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if (ec2)
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break;
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}
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if (!ec2 &&
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item2_type == cur_em->em_datatype &&
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equal(item2, cur_em->em_expr))
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{
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ec2 = cur_ec;
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em2 = cur_em;
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if (ec1)
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break;
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}
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}
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if (ec1 && ec2)
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break;
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}
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/* Sweep finished, what did we find? */
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if (ec1 && ec2)
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{
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/* If case 1, nothing to do, except add to sources */
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if (ec1 == ec2)
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{
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ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
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ec1->ec_below_outer_join |= below_outer_join;
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/* mark the RI as usable with this pair of EMs */
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/* NB: can't set left_ec/right_ec until merging is finished */
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restrictinfo->left_em = em1;
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restrictinfo->right_em = em2;
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return true;
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}
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/*
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* Case 2: need to merge ec1 and ec2. We add ec2's items to ec1,
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* then set ec2's ec_merged link to point to ec1 and remove ec2
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* from the eq_classes list. We cannot simply delete ec2 because
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* that could leave dangling pointers in existing PathKeys. We
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* leave it behind with a link so that the merged EC can be found.
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*/
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ec1->ec_members = list_concat(ec1->ec_members, ec2->ec_members);
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ec1->ec_sources = list_concat(ec1->ec_sources, ec2->ec_sources);
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ec1->ec_derives = list_concat(ec1->ec_derives, ec2->ec_derives);
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ec1->ec_relids = bms_join(ec1->ec_relids, ec2->ec_relids);
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ec1->ec_has_const |= ec2->ec_has_const;
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/* can't need to set has_volatile */
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ec1->ec_below_outer_join |= ec2->ec_below_outer_join;
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ec2->ec_merged = ec1;
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root->eq_classes = list_delete_ptr(root->eq_classes, ec2);
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/* just to avoid debugging confusion w/ dangling pointers: */
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ec2->ec_members = NIL;
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ec2->ec_sources = NIL;
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ec2->ec_derives = NIL;
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ec2->ec_relids = NULL;
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ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
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ec1->ec_below_outer_join |= below_outer_join;
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/* mark the RI as usable with this pair of EMs */
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restrictinfo->left_em = em1;
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restrictinfo->right_em = em2;
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}
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else if (ec1)
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{
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/* Case 3: add item2 to ec1 */
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em2 = add_eq_member(ec1, item2, item2_relids, false, item2_type);
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ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
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ec1->ec_below_outer_join |= below_outer_join;
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/* mark the RI as usable with this pair of EMs */
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restrictinfo->left_em = em1;
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restrictinfo->right_em = em2;
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}
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else if (ec2)
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{
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/* Case 3: add item1 to ec2 */
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em1 = add_eq_member(ec2, item1, item1_relids, false, item1_type);
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ec2->ec_sources = lappend(ec2->ec_sources, restrictinfo);
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ec2->ec_below_outer_join |= below_outer_join;
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/* mark the RI as usable with this pair of EMs */
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restrictinfo->left_em = em1;
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restrictinfo->right_em = em2;
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}
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else
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{
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/* Case 4: make a new, two-entry EC */
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EquivalenceClass *ec = makeNode(EquivalenceClass);
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ec->ec_opfamilies = opfamilies;
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ec->ec_members = NIL;
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ec->ec_sources = list_make1(restrictinfo);
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ec->ec_derives = NIL;
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ec->ec_relids = NULL;
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ec->ec_has_const = false;
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ec->ec_has_volatile = false;
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ec->ec_below_outer_join = below_outer_join;
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ec->ec_broken = false;
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ec->ec_merged = NULL;
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em1 = add_eq_member(ec, item1, item1_relids, false, item1_type);
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em2 = add_eq_member(ec, item2, item2_relids, false, item2_type);
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root->eq_classes = lappend(root->eq_classes, ec);
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/* mark the RI as usable with this pair of EMs */
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restrictinfo->left_em = em1;
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restrictinfo->right_em = em2;
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}
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return true;
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}
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/*
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* add_eq_member - build a new EquivalenceMember and add it to an EC
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*/
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static EquivalenceMember *
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add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
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bool is_child, Oid datatype)
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{
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EquivalenceMember *em = makeNode(EquivalenceMember);
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em->em_expr = expr;
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em->em_relids = relids;
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em->em_is_const = false;
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em->em_is_child = is_child;
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em->em_datatype = datatype;
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if (bms_is_empty(relids))
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{
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/*
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* No Vars, assume it's a pseudoconstant. This is correct for
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* entries generated from process_equivalence(), because a WHERE
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* clause can't contain aggregates or SRFs, and non-volatility was
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* checked before process_equivalence() ever got called. But
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* get_eclass_for_sort_expr() has to work harder. We put the tests
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* there not here to save cycles in the equivalence case.
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*/
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Assert(!is_child);
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em->em_is_const = true;
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ec->ec_has_const = true;
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/* it can't affect ec_relids */
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}
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else if (!is_child) /* child members don't add to ec_relids */
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{
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ec->ec_relids = bms_add_members(ec->ec_relids, relids);
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}
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ec->ec_members = lappend(ec->ec_members, em);
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return em;
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}
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/*
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* get_eclass_for_sort_expr
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* Given an expression and opfamily info, find an existing equivalence
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* class it is a member of; if none, build a new single-member
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* EquivalenceClass for it.
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*
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* This can be used safely both before and after EquivalenceClass merging;
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* since it never causes merging it does not invalidate any existing ECs
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* or PathKeys.
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*
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* Note: opfamilies must be chosen consistently with the way
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* process_equivalence() would do; that is, generated from a mergejoinable
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* equality operator. Else we might fail to detect valid equivalences,
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* generating poor (but not incorrect) plans.
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*/
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EquivalenceClass *
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get_eclass_for_sort_expr(PlannerInfo *root,
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Expr *expr,
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Oid expr_datatype,
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List *opfamilies)
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{
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EquivalenceClass *newec;
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EquivalenceMember *newem;
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ListCell *lc1;
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MemoryContext oldcontext;
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/*
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* Scan through the existing EquivalenceClasses for a match
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*/
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foreach(lc1, root->eq_classes)
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{
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EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
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ListCell *lc2;
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/* we allow matching to a volatile EC here */
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if (!equal(opfamilies, cur_ec->ec_opfamilies))
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continue;
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foreach(lc2, cur_ec->ec_members)
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{
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EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
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/*
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* If below an outer join, don't match constants: they're not
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* as constant as they look.
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*/
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if (cur_ec->ec_below_outer_join &&
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cur_em->em_is_const)
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continue;
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if (expr_datatype == cur_em->em_datatype &&
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equal(expr, cur_em->em_expr))
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return cur_ec; /* Match! */
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}
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}
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/*
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* No match, so build a new single-member EC
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*
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* Here, we must be sure that we construct the EC in the right context.
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* We can assume, however, that the passed expr is long-lived.
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*/
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oldcontext = MemoryContextSwitchTo(root->planner_cxt);
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newec = makeNode(EquivalenceClass);
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newec->ec_opfamilies = list_copy(opfamilies);
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newec->ec_members = NIL;
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newec->ec_sources = NIL;
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newec->ec_derives = NIL;
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newec->ec_relids = NULL;
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newec->ec_has_const = false;
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newec->ec_has_volatile = contain_volatile_functions((Node *) expr);
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newec->ec_below_outer_join = false;
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newec->ec_broken = false;
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newec->ec_merged = NULL;
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newem = add_eq_member(newec, expr, pull_varnos((Node *) expr),
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false, expr_datatype);
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/*
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* add_eq_member doesn't check for volatile functions, set-returning
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* functions, or aggregates, but such could appear in sort expressions;
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* so we have to check whether its const-marking was correct.
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*/
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if (newec->ec_has_const)
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{
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if (newec->ec_has_volatile ||
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expression_returns_set((Node *) expr) ||
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contain_agg_clause((Node *) expr))
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{
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newec->ec_has_const = false;
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newem->em_is_const = false;
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}
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}
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root->eq_classes = lappend(root->eq_classes, newec);
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MemoryContextSwitchTo(oldcontext);
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return newec;
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}
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|
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/*
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* generate_base_implied_equalities
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* Generate any restriction clauses that we can deduce from equivalence
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* classes.
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*
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* When an EC contains pseudoconstants, our strategy is to generate
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* "member = const1" clauses where const1 is the first constant member, for
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* every other member (including other constants). If we are able to do this
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* then we don't need any "var = var" comparisons because we've successfully
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* constrained all the vars at their points of creation. If we fail to
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* generate any of these clauses due to lack of cross-type operators, we fall
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* back to the "ec_broken" strategy described below. (XXX if there are
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* multiple constants of different types, it's possible that we might succeed
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* in forming all the required clauses if we started from a different const
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* member; but this seems a sufficiently hokey corner case to not be worth
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* spending lots of cycles on.)
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*
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* For ECs that contain no pseudoconstants, we generate derived clauses
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* "member1 = member2" for each pair of members belonging to the same base
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* relation (actually, if there are more than two for the same base relation,
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* 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 for matches, nor put the created RestrictInfos
|
|
* into ec_derives. Doing so would require some slightly ugly changes in
|
|
* initsplan.c's API, and there's no real advantage, because the clauses
|
|
* generated here can't duplicate anything we will generate for joins anyway.
|
|
*/
|
|
void
|
|
generate_base_implied_equalities(PlannerInfo *root)
|
|
{
|
|
ListCell *lc;
|
|
Index rti;
|
|
|
|
foreach(lc, root->eq_classes)
|
|
{
|
|
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
|
|
|
|
Assert(ec->ec_merged == NULL); /* else shouldn't be in list */
|
|
Assert(!ec->ec_broken); /* not yet anyway... */
|
|
|
|
/* Single-member ECs won't generate any deductions */
|
|
if (list_length(ec->ec_members) <= 1)
|
|
continue;
|
|
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* This is also a handy place to mark base rels (which should all
|
|
* exist by now) with flags showing whether they have pending eclass
|
|
* joins.
|
|
*/
|
|
for (rti = 1; rti < root->simple_rel_array_size; rti++)
|
|
{
|
|
RelOptInfo *brel = root->simple_rel_array[rti];
|
|
|
|
if (brel == NULL)
|
|
continue;
|
|
|
|
brel->has_eclass_joins = has_relevant_eclass_joinclause(root, brel);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/* Find the constant member to use */
|
|
foreach(lc, ec->ec_members)
|
|
{
|
|
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
|
|
|
|
if (cur_em->em_is_const)
|
|
{
|
|
const_em = cur_em;
|
|
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;
|
|
|
|
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;
|
|
}
|
|
process_implied_equality(root, eq_op,
|
|
cur_em->em_expr, const_em->em_expr,
|
|
ec->ec_relids,
|
|
ec->ec_below_outer_join,
|
|
cur_em->em_is_const);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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_mem = cur_mem". 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_membership(cur_em->em_relids) != BMS_SINGLETON)
|
|
continue;
|
|
relid = bms_singleton_member(cur_em->em_relids);
|
|
Assert(relid < root->simple_rel_array_size);
|
|
|
|
if (prev_ems[relid] != NULL)
|
|
{
|
|
EquivalenceMember *prev_em = prev_ems[relid];
|
|
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;
|
|
break;
|
|
}
|
|
process_implied_equality(root, eq_op,
|
|
prev_em->em_expr, cur_em->em_expr,
|
|
ec->ec_relids,
|
|
ec->ec_below_outer_join,
|
|
false);
|
|
}
|
|
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, false);
|
|
|
|
add_vars_to_targetlist(root, vars, ec->ec_relids);
|
|
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.)
|
|
*/
|
|
static void
|
|
generate_base_implied_equalities_broken(PlannerInfo *root,
|
|
EquivalenceClass *ec)
|
|
{
|
|
ListCell *lc;
|
|
|
|
foreach(lc, ec->ec_sources)
|
|
{
|
|
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
|
|
|
|
if (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
|
|
* path pair. Hence a fresh List of RestrictInfo nodes is built and passed
|
|
* back on each call.
|
|
*
|
|
* 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 nestloop-with-inner-indexscan join, however. 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 in createplan.c.
|
|
*
|
|
* 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.
|
|
*/
|
|
List *
|
|
generate_join_implied_equalities(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outer_rel,
|
|
RelOptInfo *inner_rel)
|
|
{
|
|
List *result = NIL;
|
|
ListCell *lc;
|
|
|
|
foreach(lc, root->eq_classes)
|
|
{
|
|
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, joinrel->relids))
|
|
continue;
|
|
|
|
if (!ec->ec_broken)
|
|
sublist = generate_join_implied_equalities_normal(root,
|
|
ec,
|
|
joinrel,
|
|
outer_rel,
|
|
inner_rel);
|
|
|
|
/* Recover if we failed to generate required derived clauses */
|
|
if (ec->ec_broken)
|
|
sublist = generate_join_implied_equalities_broken(root,
|
|
ec,
|
|
joinrel,
|
|
outer_rel,
|
|
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,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outer_rel,
|
|
RelOptInfo *inner_rel)
|
|
{
|
|
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);
|
|
|
|
if (cur_em->em_is_child)
|
|
continue; /* ignore children here */
|
|
if (!bms_is_subset(cur_em->em_relids, joinrel->relids))
|
|
continue; /* ignore --- not computable yet */
|
|
|
|
if (bms_is_subset(cur_em->em_relids, outer_rel->relids))
|
|
outer_members = lappend(outer_members, cur_em);
|
|
else if (bms_is_subset(cur_em->em_relids, inner_rel->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, if enable_hashjoin is on, we 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 (!enable_hashjoin || op_hashjoinable(eq_op))
|
|
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.
|
|
*/
|
|
static List *
|
|
generate_join_implied_equalities_broken(PlannerInfo *root,
|
|
EquivalenceClass *ec,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outer_rel,
|
|
RelOptInfo *inner_rel)
|
|
{
|
|
List *result = NIL;
|
|
ListCell *lc;
|
|
|
|
foreach(lc, ec->ec_sources)
|
|
{
|
|
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
|
|
|
|
if (bms_is_subset(restrictinfo->required_relids, joinrel->relids) &&
|
|
!bms_is_subset(restrictinfo->required_relids, outer_rel->relids) &&
|
|
!bms_is_subset(restrictinfo->required_relids, inner_rel->relids))
|
|
result = lappend(result, restrictinfo);
|
|
}
|
|
|
|
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))
|
|
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(opno,
|
|
leftem->em_expr,
|
|
rightem->em_expr,
|
|
ec->ec_relids);
|
|
|
|
/* Mark the clause as redundant, or not */
|
|
rinfo->parent_ec = parent_ec;
|
|
|
|
/*
|
|
* We can set these now, rather than letting them be looked up later,
|
|
* since this is only used after EC merging is complete.
|
|
*/
|
|
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 either create EquivalenceClasses
|
|
* to replace them or 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 equivalence clause involves
|
|
* relations entirely 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.
|
|
*
|
|
* 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().
|
|
*/
|
|
void
|
|
reconsider_outer_join_clauses(PlannerInfo *root)
|
|
{
|
|
ListCell *lc;
|
|
|
|
/* Process the LEFT JOIN clauses */
|
|
foreach(lc, root->left_join_clauses)
|
|
{
|
|
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
|
|
|
|
reconsider_outer_join_clause(root, rinfo, true);
|
|
}
|
|
/* And the RIGHT JOIN clauses */
|
|
foreach(lc, root->right_join_clauses)
|
|
{
|
|
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
|
|
|
|
reconsider_outer_join_clause(root, rinfo, false);
|
|
}
|
|
/* And the FULL JOIN clauses */
|
|
foreach(lc, root->full_join_clauses)
|
|
{
|
|
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
|
|
|
|
reconsider_full_join_clause(root, rinfo);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* reconsider_outer_join_clauses for a single LEFT/RIGHT JOIN clause
|
|
*/
|
|
static void
|
|
reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo,
|
|
bool outer_on_left)
|
|
{
|
|
Expr *outervar,
|
|
*innervar;
|
|
Oid left_type,
|
|
right_type,
|
|
inner_datatype;
|
|
ListCell *lc1;
|
|
|
|
/* Extract needed info from the clause */
|
|
Assert(is_opclause(rinfo->clause));
|
|
op_input_types(((OpExpr *) rinfo->clause)->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;
|
|
}
|
|
else
|
|
{
|
|
outervar = (Expr *) get_rightop(rinfo->clause);
|
|
innervar = (Expr *) get_leftop(rinfo->clause);
|
|
inner_datatype = left_type;
|
|
}
|
|
|
|
/* 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 opfamilies, too */
|
|
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);
|
|
|
|
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(eq_op,
|
|
innervar,
|
|
cur_em->em_expr,
|
|
cur_ec->ec_relids);
|
|
if (process_equivalence(root, newrinfo, true))
|
|
match = true;
|
|
}
|
|
|
|
/*
|
|
* If we were able to equate INNERVAR to any constant, we're done, and
|
|
* we can throw away the outer-join clause as redundant. Otherwise,
|
|
* fall out of the search loop, since we know the OUTERVAR appears in
|
|
* at most one EC.
|
|
*/
|
|
if (match)
|
|
return;
|
|
else
|
|
break;
|
|
}
|
|
|
|
/* We did not find a match, so throw it back into regular processing */
|
|
distribute_restrictinfo_to_rels(root, rinfo);
|
|
}
|
|
|
|
/*
|
|
* reconsider_outer_join_clauses for a single FULL JOIN clause
|
|
*/
|
|
static void
|
|
reconsider_full_join_clause(PlannerInfo *root, RestrictInfo *rinfo)
|
|
{
|
|
Expr *leftvar;
|
|
Expr *rightvar;
|
|
Oid left_type,
|
|
right_type;
|
|
ListCell *lc1;
|
|
|
|
/* Extract needed info from the clause */
|
|
Assert(is_opclause(rinfo->clause));
|
|
leftvar = (Expr *) get_leftop(rinfo->clause);
|
|
rightvar = (Expr *) get_rightop(rinfo->clause);
|
|
op_input_types(((OpExpr *) rinfo->clause)->opno,
|
|
&left_type, &right_type);
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
|
|
EquivalenceMember *coal_em = NULL;
|
|
bool match;
|
|
bool matchleft;
|
|
bool matchright;
|
|
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 opfamilies, too */
|
|
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);
|
|
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))
|
|
{
|
|
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(eq_op,
|
|
leftvar,
|
|
cur_em->em_expr,
|
|
cur_ec->ec_relids);
|
|
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(eq_op,
|
|
rightvar,
|
|
cur_em->em_expr,
|
|
cur_ec->ec_relids);
|
|
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_ptr(cur_ec->ec_members, coal_em);
|
|
return;
|
|
}
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/* We did not find a match, so throw it back into regular processing */
|
|
distribute_restrictinfo_to_rels(root, rinfo);
|
|
}
|
|
|
|
|
|
/*
|
|
* 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 (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;
|
|
}
|
|
|
|
|
|
/*
|
|
* add_child_rel_equivalences
|
|
* Search for EC members that reference (only) the parent_rel, and
|
|
* add transformed members referencing the child_rel.
|
|
*
|
|
* We only need to do this for ECs that could generate join conditions,
|
|
* since the child members are only used for creating inner-indexscan paths.
|
|
*
|
|
* 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.
|
|
*/
|
|
void
|
|
add_child_rel_equivalences(PlannerInfo *root,
|
|
AppendRelInfo *appinfo,
|
|
RelOptInfo *parent_rel,
|
|
RelOptInfo *child_rel)
|
|
{
|
|
ListCell *lc1;
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
|
|
ListCell *lc2;
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/* No point in searching if parent rel not mentioned in eclass */
|
|
if (!bms_is_subset(parent_rel->relids, cur_ec->ec_relids))
|
|
continue;
|
|
|
|
foreach(lc2, cur_ec->ec_members)
|
|
{
|
|
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
|
|
|
|
/* Does it reference (only) parent_rel? */
|
|
if (bms_equal(cur_em->em_relids, parent_rel->relids))
|
|
{
|
|
/* Yes, generate transformed child version */
|
|
Expr *child_expr;
|
|
|
|
child_expr = (Expr *)
|
|
adjust_appendrel_attrs((Node *) cur_em->em_expr,
|
|
appinfo);
|
|
(void) add_eq_member(cur_ec, child_expr, child_rel->relids,
|
|
true, cur_em->em_datatype);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* find_eclass_clauses_for_index_join
|
|
* Create joinclauses usable for a nestloop-with-inner-indexscan
|
|
* scanning the given inner rel with the specified set of outer rels.
|
|
*/
|
|
List *
|
|
find_eclass_clauses_for_index_join(PlannerInfo *root, RelOptInfo *rel,
|
|
Relids outer_relids)
|
|
{
|
|
List *result = NIL;
|
|
bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
|
|
ListCell *lc1;
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
|
|
ListCell *lc2;
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/*
|
|
* No point in searching if rel not mentioned in eclass (but we
|
|
* can't tell that for a child rel).
|
|
*/
|
|
if (!is_child_rel &&
|
|
!bms_is_subset(rel->relids, cur_ec->ec_relids))
|
|
continue;
|
|
/* ... nor if no overlap with outer_relids */
|
|
if (!bms_overlap(outer_relids, cur_ec->ec_relids))
|
|
continue;
|
|
|
|
/* Scan members, looking for indexable columns */
|
|
foreach(lc2, cur_ec->ec_members)
|
|
{
|
|
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
|
|
EquivalenceMember *best_outer_em = NULL;
|
|
Oid best_eq_op = InvalidOid;
|
|
ListCell *lc3;
|
|
|
|
if (!bms_equal(cur_em->em_relids, rel->relids) ||
|
|
!eclass_matches_any_index(cur_ec, cur_em, rel))
|
|
continue;
|
|
|
|
/*
|
|
* Found one, so try to generate a join clause. This is like
|
|
* generate_join_implied_equalities_normal, except simpler
|
|
* since our only preference item is to pick a Var on the
|
|
* outer side. We only need one join clause per index col.
|
|
*/
|
|
foreach(lc3, cur_ec->ec_members)
|
|
{
|
|
EquivalenceMember *outer_em = (EquivalenceMember *) lfirst(lc3);
|
|
Oid eq_op;
|
|
|
|
if (!bms_is_subset(outer_em->em_relids, outer_relids))
|
|
continue;
|
|
eq_op = select_equality_operator(cur_ec,
|
|
cur_em->em_datatype,
|
|
outer_em->em_datatype);
|
|
if (!OidIsValid(eq_op))
|
|
continue;
|
|
best_outer_em = outer_em;
|
|
best_eq_op = eq_op;
|
|
if (IsA(outer_em->em_expr, Var) ||
|
|
(IsA(outer_em->em_expr, RelabelType) &&
|
|
IsA(((RelabelType *) outer_em->em_expr)->arg, Var)))
|
|
break; /* no need to look further */
|
|
}
|
|
|
|
if (best_outer_em)
|
|
{
|
|
/* Found a suitable joinclause */
|
|
RestrictInfo *rinfo;
|
|
|
|
/* set parent_ec to mark as redundant with other joinclauses */
|
|
rinfo = create_join_clause(root, cur_ec, best_eq_op,
|
|
cur_em, best_outer_em,
|
|
cur_ec);
|
|
|
|
result = lappend(result, rinfo);
|
|
/*
|
|
* Note: we keep scanning here because we want to provide
|
|
* a clause for every possible indexcol.
|
|
*/
|
|
}
|
|
}
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
|
|
/*
|
|
* have_relevant_eclass_joinclause
|
|
* Detect whether there is an EquivalenceClass that could produce
|
|
* a joinclause between 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)
|
|
{
|
|
ListCell *lc1;
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
|
|
bool has_rel1;
|
|
bool has_rel2;
|
|
ListCell *lc2;
|
|
|
|
/*
|
|
* Won't generate joinclauses if const or single-member (the latter
|
|
* test covers the volatile case too)
|
|
*/
|
|
if (ec->ec_has_const || list_length(ec->ec_members) <= 1)
|
|
continue;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
|
|
/* Needn't scan if it couldn't contain members from each rel */
|
|
if (!bms_overlap(rel1->relids, ec->ec_relids) ||
|
|
!bms_overlap(rel2->relids, ec->ec_relids))
|
|
continue;
|
|
|
|
/* Scan the EC to see if it has member(s) in each rel */
|
|
has_rel1 = has_rel2 = false;
|
|
foreach(lc2, ec->ec_members)
|
|
{
|
|
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
|
|
|
|
if (cur_em->em_is_child)
|
|
continue; /* ignore children here */
|
|
if (bms_is_subset(cur_em->em_relids, rel1->relids))
|
|
{
|
|
has_rel1 = true;
|
|
if (has_rel2)
|
|
break;
|
|
}
|
|
if (bms_is_subset(cur_em->em_relids, rel2->relids))
|
|
{
|
|
has_rel2 = true;
|
|
if (has_rel1)
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (has_rel1 && has_rel2)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
|
|
/*
|
|
* has_relevant_eclass_joinclause
|
|
* Detect whether there is an EquivalenceClass that could produce
|
|
* a joinclause between 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)
|
|
{
|
|
ListCell *lc1;
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
|
|
bool has_rel1;
|
|
bool has_rel2;
|
|
ListCell *lc2;
|
|
|
|
/*
|
|
* Won't generate joinclauses if const or single-member (the latter
|
|
* test covers the volatile case too)
|
|
*/
|
|
if (ec->ec_has_const || list_length(ec->ec_members) <= 1)
|
|
continue;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
|
|
/* Needn't scan if it couldn't contain members from each rel */
|
|
if (!bms_overlap(rel1->relids, ec->ec_relids) ||
|
|
bms_is_subset(ec->ec_relids, rel1->relids))
|
|
continue;
|
|
|
|
/* Scan the EC to see if it has member(s) in each rel */
|
|
has_rel1 = has_rel2 = false;
|
|
foreach(lc2, ec->ec_members)
|
|
{
|
|
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
|
|
|
|
if (cur_em->em_is_child)
|
|
continue; /* ignore children here */
|
|
if (bms_is_subset(cur_em->em_relids, rel1->relids))
|
|
{
|
|
has_rel1 = true;
|
|
if (has_rel2)
|
|
break;
|
|
}
|
|
if (!bms_overlap(cur_em->em_relids, rel1->relids))
|
|
{
|
|
has_rel2 = true;
|
|
if (has_rel1)
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (has_rel1 && has_rel2)
|
|
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(EquivalenceClass *eclass,
|
|
RelOptInfo *rel)
|
|
{
|
|
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 rel already includes all members of eclass, no point in searching */
|
|
if (bms_is_subset(eclass->ec_relids, rel->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 &&
|
|
!bms_overlap(cur_em->em_relids, rel->relids))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|