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e3ffd05b02
We should be willing to cross-join two small relations if that allows us to use an inner indexscan on a large relation (that is, the potential indexqual for the large table requires both smaller relations). This worked in simple cases but fell apart as soon as there was a join clause to a fourth relation, because the existence of any two-relation join clause caused the planner to not consider clauseless joins between other base relations. The added regression test shows an example case adapted from a recent complaint from Benoit Delbosc. Adjust have_relevant_joinclause, have_relevant_eclass_joinclause, and has_relevant_eclass_joinclause to consider that a join clause mentioning three or more relations is sufficient grounds for joining any subset of those relations, even if we have to do so via a cartesian join. Since such clauses are relatively uncommon, this shouldn't affect planning speed on typical queries; in fact it should help a bit, because the latter two functions in particular get significantly simpler. Although this is arguably a bug fix, I'm not going to risk back-patching it, since it might have currently-unforeseen consequences.
2177 lines
68 KiB
C
2177 lines
68 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) 1996-2012, 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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* src/backend/optimizer/path/equivclass.c
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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 "catalog/pg_type.h"
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#include "nodes/makefuncs.h"
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#include "nodes/nodeFuncs.h"
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#include "optimizer/clauses.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 bool 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 bool reconsider_full_join_clause(PlannerInfo *root,
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RestrictInfo *rinfo);
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static Index get_parent_relid(PlannerInfo *root, RelOptInfo *rel);
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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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* On success return, we have also initialized the clause's left_ec/right_ec
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* fields to point to the EquivalenceClass representing it. This saves lookup
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* effort later.
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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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collation,
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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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/* Should not already be marked as having generated an eclass */
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Assert(restrictinfo->left_ec == NULL);
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Assert(restrictinfo->right_ec == NULL);
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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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collation = ((OpExpr *) clause)->inputcollid;
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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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* Ensure both input expressions expose the desired collation (their types
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* should be OK already); see comments for canonicalize_ec_expression.
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*/
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item1 = canonicalize_ec_expression(item1,
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exprType((Node *) item1),
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collation);
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item2 = canonicalize_ec_expression(item2,
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exprType((Node *) item2),
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collation);
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/*
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* Reject clauses of the form X=X. These are not as redundant as they
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* might seem at first glance: assuming the operator is strict, this is
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* really an expensive way to write X IS NOT NULL. So we must not risk
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* just losing the clause, which would be possible if there is already a
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* single-element EquivalenceClass containing X. The case is not common
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* enough to be worth contorting the EC machinery for, so just reject the
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* clause and let it be processed as a normal restriction clause.
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*/
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if (equal(item1, item2))
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return false; /* X=X is not a useful equivalence */
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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 the
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* inputs, as the nominal datatypes for opfamily lookup. This presumes
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* that btree operators are always registered with amoplefttype and
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* amoprighttype equal to their declared input types. We will need this
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* info anyway to build EquivalenceMember nodes, and by extracting it now
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* 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 to
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* 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, so
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* 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 or the similar
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* search in get_eclass_for_sort_expr(), it's impossible that we'd match
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* an item in more than one existing nonvolatile EC. So it's okay to stop
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* at the first match.
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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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* The collation has to match; check this first since it's cheaper
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* than the opfamily comparison.
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*/
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if (collation != cur_ec->ec_collation)
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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 as
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* 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 associated with this eclass */
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restrictinfo->left_ec = ec1;
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restrictinfo->right_ec = ec1;
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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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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, then
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* set ec2's ec_merged link to point to ec1 and remove ec2 from the
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* eq_classes list. We cannot simply delete ec2 because that could
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* leave dangling pointers in existing PathKeys. We leave it behind
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* 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 associated with this eclass */
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restrictinfo->left_ec = ec1;
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restrictinfo->right_ec = ec1;
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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 associated with this eclass */
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restrictinfo->left_ec = ec1;
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restrictinfo->right_ec = ec1;
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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 associated with this eclass */
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restrictinfo->left_ec = ec2;
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restrictinfo->right_ec = ec2;
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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_collation = collation;
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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_sortref = 0;
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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 associated with this eclass */
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restrictinfo->left_ec = ec;
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restrictinfo->right_ec = 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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* canonicalize_ec_expression
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*
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* This function ensures that the expression exposes the expected type and
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* collation, so that it will be equal() to other equivalence-class expressions
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* that it ought to be equal() to.
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*
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* The rule for datatypes is that the exposed type should match what it would
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* be for an input to an operator of the EC's opfamilies; which is usually
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* the declared input type of the operator, but in the case of polymorphic
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* operators no relabeling is wanted (compare the behavior of parse_coerce.c).
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* Expressions coming in from quals will generally have the right type
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* already, but expressions coming from indexkeys may not (because they are
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* represented without any explicit relabel in pg_index), and the same problem
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* occurs for sort expressions (because the parser is likewise cavalier about
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* putting relabels on them). Such cases will be binary-compatible with the
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* real operators, so adding a RelabelType is sufficient.
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*
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* Also, the expression's exposed collation must match the EC's collation.
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* This is important because in comparisons like "foo < bar COLLATE baz",
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* only one of the expressions has the correct exposed collation as we receive
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* it from the parser. Forcing both of them to have it ensures that all
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* variant spellings of such a construct behave the same. Again, we can
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* stick on a RelabelType to force the right exposed collation. (It might
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* work to not label the collation at all in EC members, but this is risky
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* since some parts of the system expect exprCollation() to deliver the
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* right answer for a sort key.)
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*
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* Note this code assumes that the expression has already been through
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* eval_const_expressions, so there are no CollateExprs and no redundant
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* RelabelTypes.
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*/
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Expr *
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canonicalize_ec_expression(Expr *expr, Oid req_type, Oid req_collation)
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{
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Oid expr_type = exprType((Node *) expr);
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/*
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* For a polymorphic-input-type opclass, just keep the same exposed type.
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*/
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if (IsPolymorphicType(req_type))
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req_type = expr_type;
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/*
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* No work if the expression exposes the right type/collation already.
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*/
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if (expr_type != req_type ||
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exprCollation((Node *) expr) != req_collation)
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{
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/*
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* Strip any existing RelabelType, then add a new one if needed. This
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* is to preserve the invariant of no redundant RelabelTypes.
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*
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* If we have to change the exposed type of the stripped expression,
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* set typmod to -1 (since the new type may not have the same typmod
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* interpretation). If we only have to change collation, preserve the
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* exposed typmod.
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*/
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while (expr && IsA(expr, RelabelType))
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expr = (Expr *) ((RelabelType *) expr)->arg;
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if (exprType((Node *) expr) != req_type)
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expr = (Expr *) makeRelabelType(expr,
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req_type,
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-1,
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req_collation,
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COERCE_DONTCARE);
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else if (exprCollation((Node *) expr) != req_collation)
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expr = (Expr *) makeRelabelType(expr,
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req_type,
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exprTypmod((Node *) expr),
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req_collation,
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COERCE_DONTCARE);
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}
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return expr;
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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))
|
|
{
|
|
/*
|
|
* 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.
|
|
*
|
|
* 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_indexcol 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,
|
|
List *opfamilies,
|
|
Oid opcintype,
|
|
Oid collation,
|
|
Index sortref,
|
|
Relids rel,
|
|
bool create_it)
|
|
{
|
|
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_merged = NULL;
|
|
|
|
if (newec->ec_has_volatile && sortref == 0) /* should not happen */
|
|
elog(ERROR, "volatile EquivalenceClass has no sortref");
|
|
|
|
newem = add_eq_member(newec, copyObject(expr), pull_varnos((Node *) expr),
|
|
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);
|
|
|
|
MemoryContextSwitchTo(oldcontext);
|
|
|
|
return newec;
|
|
}
|
|
|
|
|
|
/*
|
|
* 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 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;
|
|
|
|
/*
|
|
* 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 */
|
|
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, ec->ec_collation,
|
|
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, ec->ec_collation,
|
|
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,
|
|
PVC_RECURSE_AGGREGATES,
|
|
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.)
|
|
*/
|
|
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-parameterized-inner-scan. 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, 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.
|
|
*/
|
|
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,
|
|
ec->ec_collation,
|
|
leftem->em_expr,
|
|
rightem->em_expr,
|
|
bms_union(leftem->em_relids,
|
|
rightem->em_relids));
|
|
|
|
/* 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;
|
|
ListCell *prev;
|
|
ListCell *next;
|
|
|
|
/* Outer loop repeats until we find no more deductions */
|
|
do
|
|
{
|
|
found = false;
|
|
|
|
/* Process the LEFT JOIN clauses */
|
|
prev = NULL;
|
|
for (cell = list_head(root->left_join_clauses); cell; cell = next)
|
|
{
|
|
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
|
|
|
|
next = lnext(cell);
|
|
if (reconsider_outer_join_clause(root, rinfo, true))
|
|
{
|
|
found = true;
|
|
/* remove it from the list */
|
|
root->left_join_clauses =
|
|
list_delete_cell(root->left_join_clauses, cell, prev);
|
|
/* 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);
|
|
}
|
|
else
|
|
prev = cell;
|
|
}
|
|
|
|
/* Process the RIGHT JOIN clauses */
|
|
prev = NULL;
|
|
for (cell = list_head(root->right_join_clauses); cell; cell = next)
|
|
{
|
|
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
|
|
|
|
next = lnext(cell);
|
|
if (reconsider_outer_join_clause(root, rinfo, false))
|
|
{
|
|
found = true;
|
|
/* remove it from the list */
|
|
root->right_join_clauses =
|
|
list_delete_cell(root->right_join_clauses, cell, prev);
|
|
/* 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);
|
|
}
|
|
else
|
|
prev = cell;
|
|
}
|
|
|
|
/* Process the FULL JOIN clauses */
|
|
prev = NULL;
|
|
for (cell = list_head(root->full_join_clauses); cell; cell = next)
|
|
{
|
|
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
|
|
|
|
next = lnext(cell);
|
|
if (reconsider_full_join_clause(root, rinfo))
|
|
{
|
|
found = true;
|
|
/* remove it from the list */
|
|
root->full_join_clauses =
|
|
list_delete_cell(root->full_join_clauses, cell, prev);
|
|
/* 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);
|
|
}
|
|
else
|
|
prev = cell;
|
|
}
|
|
} 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;
|
|
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;
|
|
}
|
|
|
|
/* 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(eq_op,
|
|
cur_ec->ec_collation,
|
|
innervar,
|
|
cur_em->em_expr,
|
|
inner_relids);
|
|
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;
|
|
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;
|
|
|
|
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 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))
|
|
{
|
|
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,
|
|
cur_ec->ec_collation,
|
|
leftvar,
|
|
cur_em->em_expr,
|
|
left_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,
|
|
cur_ec->ec_collation,
|
|
rightvar,
|
|
cur_em->em_expr,
|
|
right_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 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;
|
|
}
|
|
|
|
|
|
/*
|
|
* add_child_rel_equivalences
|
|
* Search for EC members that reference (only) the parent_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.
|
|
*/
|
|
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;
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/* 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);
|
|
|
|
if (cur_em->em_is_child)
|
|
continue; /* ignore children here */
|
|
|
|
/* 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(root,
|
|
(Node *) cur_em->em_expr,
|
|
appinfo);
|
|
(void) add_eq_member(cur_ec, child_expr, child_rel->relids,
|
|
true, cur_em->em_datatype);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* mutate_eclass_expressions
|
|
* Apply an expression tree mutator to all expressions stored in
|
|
* equivalence classes.
|
|
*
|
|
* This is a bit of a hack ... it's currently needed only by planagg.c,
|
|
* which needs to do a global search-and-replace of MIN/MAX Aggrefs
|
|
* after eclasses are already set up. Without changing the eclasses too,
|
|
* subsequent matching of ORDER BY clauses would fail.
|
|
*
|
|
* Note that we assume the mutation won't affect relation membership or any
|
|
* other properties we keep track of (which is a bit bogus, but by the time
|
|
* planagg.c runs, it no longer matters). Also we must be called in the
|
|
* main planner memory context.
|
|
*/
|
|
void
|
|
mutate_eclass_expressions(PlannerInfo *root,
|
|
Node *(*mutator) (),
|
|
void *context)
|
|
{
|
|
ListCell *lc1;
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
|
|
ListCell *lc2;
|
|
|
|
foreach(lc2, cur_ec->ec_members)
|
|
{
|
|
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
|
|
|
|
cur_em->em_expr = (Expr *)
|
|
mutator((Node *) cur_em->em_expr, context);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* generate_implied_equalities_for_indexcol
|
|
* Create EC-derived joinclauses usable with a specific index column.
|
|
*
|
|
* We assume that any given 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 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 indexscan, 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.)
|
|
*/
|
|
List *
|
|
generate_implied_equalities_for_indexcol(PlannerInfo *root,
|
|
IndexOptInfo *index,
|
|
int indexcol)
|
|
{
|
|
List *result = NIL;
|
|
RelOptInfo *rel = index->rel;
|
|
bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
|
|
Index parent_relid;
|
|
ListCell *lc1;
|
|
|
|
/* If it's a child rel, we'll need to know what its parent is */
|
|
if (is_child_rel)
|
|
parent_relid = get_parent_relid(root, rel);
|
|
else
|
|
parent_relid = 0; /* not used, but keep compiler quiet */
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
|
|
EquivalenceMember *cur_em;
|
|
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;
|
|
|
|
/*
|
|
* Scan members, looking for a match to the indexable 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 index
|
|
* 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) &&
|
|
eclass_member_matches_indexcol(cur_ec, cur_em,
|
|
index, indexcol))
|
|
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;
|
|
|
|
/*
|
|
* Also, if this is a child rel, avoid generating a useless join
|
|
* to its parent rel.
|
|
*/
|
|
if (is_child_rel &&
|
|
bms_is_member(parent_relid, 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;
|
|
}
|
|
|
|
/*
|
|
* get_parent_relid
|
|
* Get the relid of a child rel's parent appendrel
|
|
*
|
|
* Possibly this should be somewhere else, but right now the logic is only
|
|
* needed here.
|
|
*/
|
|
static Index
|
|
get_parent_relid(PlannerInfo *root, RelOptInfo *rel)
|
|
{
|
|
ListCell *lc;
|
|
|
|
foreach(lc, root->append_rel_list)
|
|
{
|
|
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
|
|
|
|
if (appinfo->child_relid == rel->relid)
|
|
return appinfo->parent_relid;
|
|
}
|
|
/* should have found the entry ... */
|
|
elog(ERROR, "child rel not found in append_rel_list");
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
ListCell *lc1;
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
|
|
|
|
/*
|
|
* 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 a test on ec_relids is 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.
|
|
*/
|
|
if (bms_overlap(rel1->relids, ec->ec_relids) &&
|
|
bms_overlap(rel2->relids, ec->ec_relids))
|
|
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)
|
|
{
|
|
ListCell *lc1;
|
|
|
|
foreach(lc1, root->eq_classes)
|
|
{
|
|
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
|
|
|
|
/*
|
|
* 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_overlap(rel1->relids, ec->ec_relids) &&
|
|
!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(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)
|
|
continue; /* ignore children here */
|
|
|
|
if (!bms_overlap(cur_em->em_relids, rel->relids))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|