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postgres/src/backend/optimizer/path/equivclass.c
Tom Lane 03107b4eda Ensure generated join clauses for child rels have correct relids. 
When building a join clause derived from an EquivalenceClass, if the
clause is to be used with an appendrel child relation then make sure
its clause_relids include the relids of that child relation.
Normally this would be true already because the EquivalenceMember
would be a Var of that relation.  However, if the appendrel represents
a flattened UNION ALL construct then some child EquivalenceMembers
could be constants with no relids.  The resulting under-marked clause
is problematic because it could mislead join_clause_is_movable_into
about where the clause should be evaluated.  We do not have an example
showing incorrect plan generation, but there are existing cases in
the regression tests that will fail the Asserts this patch adds to
get_baserel_parampathinfo.  A similarly wrong conclusion about a
clause being considered by get_joinrel_parampathinfo would lead to
wrong placement of the clause.  (This also squares with the way
that clause_relids is calculated for non-equijoin clauses in
adjust_appendrel_attrs.)

The other reason for wanting these new Asserts is that the previous
blithe assumption that the results of generate_join_implied_equalities
"necessarily satisfy join_clause_is_movable_into" turns out to be
wrong pre-v16.  If it's still wrong it'd be good to find out.

Per bug #18429 from Benoît Ryder.  The bug as filed was fixed by
commit 2489d76c4, but these changes correlate with the fix we
will need to apply in pre-v16 branches.

Discussion: https://postgr.es/m/18429-8982d4a348cc86c6@postgresql.org
2024-04-16 11:22:51 -04:00

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/*-------------------------------------------------------------------------
*
* equivclass.c
* Routines for managing EquivalenceClasses
*
* See src/backend/optimizer/README for discussion of EquivalenceClasses.
*
*
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/optimizer/path/equivclass.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include "access/stratnum.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/appendinfo.h"
#include "optimizer/clauses.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/restrictinfo.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"
static EquivalenceMember *add_eq_member(EquivalenceClass *ec,
Expr *expr, Relids relids,
JoinDomain *jdomain,
EquivalenceMember *parent,
Oid datatype);
static bool is_exprlist_member(Expr *node, List *exprs);
static void generate_base_implied_equalities_const(PlannerInfo *root,
EquivalenceClass *ec);
static void generate_base_implied_equalities_no_const(PlannerInfo *root,
EquivalenceClass *ec);
static void generate_base_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec);
static List *generate_join_implied_equalities_normal(PlannerInfo *root,
EquivalenceClass *ec,
Relids join_relids,
Relids outer_relids,
Relids inner_relids);
static List *generate_join_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec,
Relids nominal_join_relids,
Relids outer_relids,
Relids nominal_inner_relids,
RelOptInfo *inner_rel);
static Oid select_equality_operator(EquivalenceClass *ec,
Oid lefttype, Oid righttype);
static RestrictInfo *create_join_clause(PlannerInfo *root,
EquivalenceClass *ec, Oid opno,
EquivalenceMember *leftem,
EquivalenceMember *rightem,
EquivalenceClass *parent_ec);
static bool reconsider_outer_join_clause(PlannerInfo *root,
OuterJoinClauseInfo *ojcinfo,
bool outer_on_left);
static bool reconsider_full_join_clause(PlannerInfo *root,
OuterJoinClauseInfo *ojcinfo);
static JoinDomain *find_join_domain(PlannerInfo *root, Relids relids);
static Bitmapset *get_eclass_indexes_for_relids(PlannerInfo *root,
Relids relids);
static Bitmapset *get_common_eclass_indexes(PlannerInfo *root, Relids relids1,
Relids relids2);
/*
* process_equivalence
* The given clause has a mergejoinable operator and is not an outer-join
* qualification, so its two sides can be considered equal
* anywhere they are both computable; moreover that equality can be
* extended transitively. Record this knowledge in the EquivalenceClass
* data structure, if applicable. Returns true if successful, false if not
* (in which case caller should treat the clause as ordinary, not an
* equivalence).
*
* In some cases, although we cannot convert a clause into EquivalenceClass
* knowledge, we can still modify it to a more useful form than the original.
* Then, *p_restrictinfo will be replaced by a new RestrictInfo, which is what
* the caller should use for further processing.
*
* jdomain is the join domain within which the given clause was found.
* This limits the applicability of deductions from the EquivalenceClass,
* as described in optimizer/README.
*
* We reject proposed equivalence clauses if they contain leaky functions
* and have security_level above zero. The EC evaluation rules require us to
* apply certain tests at certain joining levels, and we can't tolerate
* delaying any test on security_level grounds. By rejecting candidate clauses
* that might require security delays, we ensure it's safe to apply an EC
* clause as soon as it's supposed to be applied.
*
* On success return, we have also initialized the clause's left_ec/right_ec
* fields to point to the EquivalenceClass representing it. This saves lookup
* effort later.
*
* Note: constructing merged EquivalenceClasses is a standard UNION-FIND
* problem, for which there exist better data structures than simple lists.
* If this code ever proves to be a bottleneck then it could be sped up ---
* but for now, simple is beautiful.
*
* Note: this is only called during planner startup, not during GEQO
* exploration, so we need not worry about whether we're in the right
* memory context.
*/
bool
process_equivalence(PlannerInfo *root,
RestrictInfo **p_restrictinfo,
JoinDomain *jdomain)
{
RestrictInfo *restrictinfo = *p_restrictinfo;
Expr *clause = restrictinfo->clause;
Oid opno,
collation,
item1_type,
item2_type;
Expr *item1;
Expr *item2;
Relids item1_relids,
item2_relids;
List *opfamilies;
EquivalenceClass *ec1,
*ec2;
EquivalenceMember *em1,
*em2;
ListCell *lc1;
int ec2_idx;
/* Should not already be marked as having generated an eclass */
Assert(restrictinfo->left_ec == NULL);
Assert(restrictinfo->right_ec == NULL);
/* Reject if it is potentially postponable by security considerations */
if (restrictinfo->security_level > 0 && !restrictinfo->leakproof)
return false;
/* Extract info from given clause */
Assert(is_opclause(clause));
opno = ((OpExpr *) clause)->opno;
collation = ((OpExpr *) clause)->inputcollid;
item1 = (Expr *) get_leftop(clause);
item2 = (Expr *) get_rightop(clause);
item1_relids = restrictinfo->left_relids;
item2_relids = restrictinfo->right_relids;
/*
* Ensure both input expressions expose the desired collation (their types
* should be OK already); see comments for canonicalize_ec_expression.
*/
item1 = canonicalize_ec_expression(item1,
exprType((Node *) item1),
collation);
item2 = canonicalize_ec_expression(item2,
exprType((Node *) item2),
collation);
/*
* Clauses of the form X=X cannot be translated into EquivalenceClasses.
* We'd either end up with a single-entry EC, losing the knowledge that
* the clause was present at all, or else make an EC with duplicate
* entries, causing other issues.
*/
if (equal(item1, item2))
{
/*
* If the operator is strict, then the clause can be treated as just
* "X IS NOT NULL". (Since we know we are considering a top-level
* qual, we can ignore the difference between FALSE and NULL results.)
* It's worth making the conversion because we'll typically get a much
* better selectivity estimate than we would for X=X.
*
* If the operator is not strict, we can't be sure what it will do
* with NULLs, so don't attempt to optimize it.
*/
set_opfuncid((OpExpr *) clause);
if (func_strict(((OpExpr *) clause)->opfuncid))
{
NullTest *ntest = makeNode(NullTest);
ntest->arg = item1;
ntest->nulltesttype = IS_NOT_NULL;
ntest->argisrow = false; /* correct even if composite arg */
ntest->location = -1;
*p_restrictinfo =
make_restrictinfo(root,
(Expr *) ntest,
restrictinfo->is_pushed_down,
restrictinfo->has_clone,
restrictinfo->is_clone,
restrictinfo->pseudoconstant,
restrictinfo->security_level,
NULL,
restrictinfo->incompatible_relids,
restrictinfo->outer_relids);
}
return false;
}
/*
* We use the declared input types of the operator, not exprType() of the
* inputs, as the nominal datatypes for opfamily lookup. This presumes
* that btree operators are always registered with amoplefttype and
* amoprighttype equal to their declared input types. We will need this
* info anyway to build EquivalenceMember nodes, and by extracting it now
* we can use type comparisons to short-circuit some equal() tests.
*/
op_input_types(opno, &item1_type, &item2_type);
opfamilies = restrictinfo->mergeopfamilies;
/*
* Sweep through the existing EquivalenceClasses looking for matches to
* item1 and item2. These are the possible outcomes:
*
* 1. We find both in the same EC. The equivalence is already known, so
* there's nothing to do.
*
* 2. We find both in different ECs. Merge the two ECs together.
*
* 3. We find just one. Add the other to its EC.
*
* 4. We find neither. Make a new, two-entry EC.
*
* Note: since all ECs are built through this process or the similar
* search in get_eclass_for_sort_expr(), it's impossible that we'd match
* an item in more than one existing nonvolatile EC. So it's okay to stop
* at the first match.
*/
ec1 = ec2 = NULL;
em1 = em2 = NULL;
ec2_idx = -1;
foreach(lc1, root->eq_classes)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
ListCell *lc2;
/* Never match to a volatile EC */
if (cur_ec->ec_has_volatile)
continue;
/*
* The collation has to match; check this first since it's cheaper
* than the opfamily comparison.
*/
if (collation != cur_ec->ec_collation)
continue;
/*
* A "match" requires matching sets of btree opfamilies. Use of
* equal() for this test has implications discussed in the comments
* for get_mergejoin_opfamilies().
*/
if (!equal(opfamilies, cur_ec->ec_opfamilies))
continue;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
Assert(!cur_em->em_is_child); /* no children yet */
/*
* Match constants only within the same JoinDomain (see
* optimizer/README).
*/
if (cur_em->em_is_const && cur_em->em_jdomain != jdomain)
continue;
if (!ec1 &&
item1_type == cur_em->em_datatype &&
equal(item1, cur_em->em_expr))
{
ec1 = cur_ec;
em1 = cur_em;
if (ec2)
break;
}
if (!ec2 &&
item2_type == cur_em->em_datatype &&
equal(item2, cur_em->em_expr))
{
ec2 = cur_ec;
ec2_idx = foreach_current_index(lc1);
em2 = cur_em;
if (ec1)
break;
}
}
if (ec1 && ec2)
break;
}
/* Sweep finished, what did we find? */
if (ec1 && ec2)
{
/* If case 1, nothing to do, except add to sources */
if (ec1 == ec2)
{
ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
ec1->ec_min_security = Min(ec1->ec_min_security,
restrictinfo->security_level);
ec1->ec_max_security = Max(ec1->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
return true;
}
/*
* Case 2: need to merge ec1 and ec2. This should never happen after
* the ECs have reached canonical state; otherwise, pathkeys could be
* rendered non-canonical by the merge, and relation eclass indexes
* would get broken by removal of an eq_classes list entry.
*/
if (root->ec_merging_done)
elog(ERROR, "too late to merge equivalence classes");
/*
* We add ec2's items to ec1, then set ec2's ec_merged link to point
* to ec1 and remove ec2 from the eq_classes list. We cannot simply
* delete ec2 because that could leave dangling pointers in existing
* PathKeys. We leave it behind with a link so that the merged EC can
* be found.
*/
ec1->ec_members = list_concat(ec1->ec_members, ec2->ec_members);
ec1->ec_sources = list_concat(ec1->ec_sources, ec2->ec_sources);
ec1->ec_derives = list_concat(ec1->ec_derives, ec2->ec_derives);
ec1->ec_relids = bms_join(ec1->ec_relids, ec2->ec_relids);
ec1->ec_has_const |= ec2->ec_has_const;
/* can't need to set has_volatile */
ec1->ec_min_security = Min(ec1->ec_min_security,
ec2->ec_min_security);
ec1->ec_max_security = Max(ec1->ec_max_security,
ec2->ec_max_security);
ec2->ec_merged = ec1;
root->eq_classes = list_delete_nth_cell(root->eq_classes, ec2_idx);
/* just to avoid debugging confusion w/ dangling pointers: */
ec2->ec_members = NIL;
ec2->ec_sources = NIL;
ec2->ec_derives = NIL;
ec2->ec_relids = NULL;
ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
ec1->ec_min_security = Min(ec1->ec_min_security,
restrictinfo->security_level);
ec1->ec_max_security = Max(ec1->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
else if (ec1)
{
/* Case 3: add item2 to ec1 */
em2 = add_eq_member(ec1, item2, item2_relids,
jdomain, NULL, item2_type);
ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
ec1->ec_min_security = Min(ec1->ec_min_security,
restrictinfo->security_level);
ec1->ec_max_security = Max(ec1->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
else if (ec2)
{
/* Case 3: add item1 to ec2 */
em1 = add_eq_member(ec2, item1, item1_relids,
jdomain, NULL, item1_type);
ec2->ec_sources = lappend(ec2->ec_sources, restrictinfo);
ec2->ec_min_security = Min(ec2->ec_min_security,
restrictinfo->security_level);
ec2->ec_max_security = Max(ec2->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec2;
restrictinfo->right_ec = ec2;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
else
{
/* Case 4: make a new, two-entry EC */
EquivalenceClass *ec = makeNode(EquivalenceClass);
ec->ec_opfamilies = opfamilies;
ec->ec_collation = collation;
ec->ec_members = NIL;
ec->ec_sources = list_make1(restrictinfo);
ec->ec_derives = NIL;
ec->ec_relids = NULL;
ec->ec_has_const = false;
ec->ec_has_volatile = false;
ec->ec_broken = false;
ec->ec_sortref = 0;
ec->ec_min_security = restrictinfo->security_level;
ec->ec_max_security = restrictinfo->security_level;
ec->ec_merged = NULL;
em1 = add_eq_member(ec, item1, item1_relids,
jdomain, NULL, item1_type);
em2 = add_eq_member(ec, item2, item2_relids,
jdomain, NULL, item2_type);
root->eq_classes = lappend(root->eq_classes, ec);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec;
restrictinfo->right_ec = ec;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
return true;
}
/*
* canonicalize_ec_expression
*
* This function ensures that the expression exposes the expected type and
* collation, so that it will be equal() to other equivalence-class expressions
* that it ought to be equal() to.
*
* The rule for datatypes is that the exposed type should match what it would
* be for an input to an operator of the EC's opfamilies; which is usually
* the declared input type of the operator, but in the case of polymorphic
* operators no relabeling is wanted (compare the behavior of parse_coerce.c).
* Expressions coming in from quals will generally have the right type
* already, but expressions coming from indexkeys may not (because they are
* represented without any explicit relabel in pg_index), and the same problem
* occurs for sort expressions (because the parser is likewise cavalier about
* putting relabels on them). Such cases will be binary-compatible with the
* real operators, so adding a RelabelType is sufficient.
*
* Also, the expression's exposed collation must match the EC's collation.
* This is important because in comparisons like "foo < bar COLLATE baz",
* only one of the expressions has the correct exposed collation as we receive
* it from the parser. Forcing both of them to have it ensures that all
* variant spellings of such a construct behave the same. Again, we can
* stick on a RelabelType to force the right exposed collation. (It might
* work to not label the collation at all in EC members, but this is risky
* since some parts of the system expect exprCollation() to deliver the
* right answer for a sort key.)
*/
Expr *
canonicalize_ec_expression(Expr *expr, Oid req_type, Oid req_collation)
{
Oid expr_type = exprType((Node *) expr);
/*
* For a polymorphic-input-type opclass, just keep the same exposed type.
* RECORD opclasses work like polymorphic-type ones for this purpose.
*/
if (IsPolymorphicType(req_type) || req_type == RECORDOID)
req_type = expr_type;
/*
* No work if the expression exposes the right type/collation already.
*/
if (expr_type != req_type ||
exprCollation((Node *) expr) != req_collation)
{
/*
* If we have to change the type of the expression, set typmod to -1,
* since the new type may not have the same typmod interpretation.
* When we only have to change collation, preserve the exposed typmod.
*/
int32 req_typmod;
if (expr_type != req_type)
req_typmod = -1;
else
req_typmod = exprTypmod((Node *) expr);
/*
* Use applyRelabelType so that we preserve const-flatness. This is
* important since eval_const_expressions has already been applied.
*/
expr = (Expr *) applyRelabelType((Node *) expr,
req_type, req_typmod, req_collation,
COERCE_IMPLICIT_CAST, -1, false);
}
return expr;
}
/*
* add_eq_member - build a new EquivalenceMember and add it to an EC
*/
static EquivalenceMember *
add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
JoinDomain *jdomain, EquivalenceMember *parent, Oid datatype)
{
EquivalenceMember *em = makeNode(EquivalenceMember);
em->em_expr = expr;
em->em_relids = relids;
em->em_is_const = false;
em->em_is_child = (parent != NULL);
em->em_datatype = datatype;
em->em_jdomain = jdomain;
em->em_parent = parent;
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(!parent);
em->em_is_const = true;
ec->ec_has_const = true;
/* it can't affect ec_relids */
}
else if (!parent) /* 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_column and match_pathkeys_to_index.)
*
* If create_it is true, we'll build a new EquivalenceClass when there is no
* match. If create_it is false, we just return NULL when no match.
*
* This can be used safely both before and after EquivalenceClass merging;
* since it never causes merging it does not invalidate any existing ECs
* or PathKeys. However, ECs added after path generation has begun are
* of limited usefulness, so usually it's best to create them beforehand.
*
* Note: opfamilies must be chosen consistently with the way
* process_equivalence() would do; that is, generated from a mergejoinable
* equality operator. Else we might fail to detect valid equivalences,
* generating poor (but not incorrect) plans.
*/
EquivalenceClass *
get_eclass_for_sort_expr(PlannerInfo *root,
Expr *expr,
List *opfamilies,
Oid opcintype,
Oid collation,
Index sortref,
Relids rel,
bool create_it)
{
JoinDomain *jdomain;
Relids expr_relids;
EquivalenceClass *newec;
EquivalenceMember *newem;
ListCell *lc1;
MemoryContext oldcontext;
/*
* Ensure the expression exposes the correct type and collation.
*/
expr = canonicalize_ec_expression(expr, opcintype, collation);
/*
* Since SortGroupClause nodes are top-level expressions (GROUP BY, ORDER
* BY, etc), they can be presumed to belong to the top JoinDomain.
*/
jdomain = linitial_node(JoinDomain, root->join_domains);
/*
* 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;
/*
* Match constants only within the same JoinDomain (see
* optimizer/README).
*/
if (cur_em->em_is_const && cur_em->em_jdomain != jdomain)
continue;
if (opcintype == cur_em->em_datatype &&
equal(expr, cur_em->em_expr))
{
/*
* Match!
*
* Copy the sortref if it wasn't set yet. That may happen if
* the ec was constructed from a WHERE clause, i.e. it doesn't
* have a target reference at all.
*/
if (cur_ec->ec_sortref == 0 && sortref > 0)
cur_ec->ec_sortref = sortref;
return cur_ec;
}
}
}
/* 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_broken = false;
newec->ec_sortref = sortref;
newec->ec_min_security = UINT_MAX;
newec->ec_max_security = 0;
newec->ec_merged = NULL;
if (newec->ec_has_volatile && sortref == 0) /* should not happen */
elog(ERROR, "volatile EquivalenceClass has no sortref");
/*
* Get the precise set of relids appearing in the expression.
*/
expr_relids = pull_varnos(root, (Node *) expr);
newem = add_eq_member(newec, copyObject(expr), expr_relids,
jdomain, NULL, opcintype);
/*
* add_eq_member doesn't check for volatile functions, set-returning
* functions, aggregates, or window functions, but such could appear in
* sort expressions; so we have to check whether its const-marking was
* correct.
*/
if (newec->ec_has_const)
{
if (newec->ec_has_volatile ||
expression_returns_set((Node *) expr) ||
contain_agg_clause((Node *) expr) ||
contain_window_function((Node *) expr))
{
newec->ec_has_const = false;
newem->em_is_const = false;
}
}
root->eq_classes = lappend(root->eq_classes, newec);
/*
* If EC merging is already complete, we have to mop up by adding the new
* EC to the eclass_indexes of the relation(s) mentioned in it.
*/
if (root->ec_merging_done)
{
int ec_index = list_length(root->eq_classes) - 1;
int i = -1;
while ((i = bms_next_member(newec->ec_relids, i)) > 0)
{
RelOptInfo *rel = root->simple_rel_array[i];
if (rel == NULL) /* must be an outer join */
{
Assert(bms_is_member(i, root->outer_join_rels));
continue;
}
Assert(rel->reloptkind == RELOPT_BASEREL);
rel->eclass_indexes = bms_add_member(rel->eclass_indexes,
ec_index);
}
}
MemoryContextSwitchTo(oldcontext);
return newec;
}
/*
* find_ec_member_matching_expr
* Locate an EquivalenceClass member matching the given expr, if any;
* return NULL if no match.
*
* "Matching" is defined as "equal after stripping RelabelTypes".
* This is used for identifying sort expressions, and we need to allow
* binary-compatible relabeling for some cases involving binary-compatible
* sort operators.
*
* Child EC members are ignored unless they belong to given 'relids'.
*/
EquivalenceMember *
find_ec_member_matching_expr(EquivalenceClass *ec,
Expr *expr,
Relids relids)
{
ListCell *lc;
/* We ignore binary-compatible relabeling on both ends */
while (expr && IsA(expr, RelabelType))
expr = ((RelabelType *) expr)->arg;
foreach(lc, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc);
Expr *emexpr;
/*
* We shouldn't be trying to sort by an equivalence class that
* contains a constant, so no need to consider such cases any further.
*/
if (em->em_is_const)
continue;
/*
* Ignore child members unless they belong to the requested rel.
*/
if (em->em_is_child &&
!bms_is_subset(em->em_relids, relids))
continue;
/*
* Match if same expression (after stripping relabel).
*/
emexpr = em->em_expr;
while (emexpr && IsA(emexpr, RelabelType))
emexpr = ((RelabelType *) emexpr)->arg;
if (equal(emexpr, expr))
return em;
}
return NULL;
}
/*
* find_computable_ec_member
* Locate an EquivalenceClass member that can be computed from the
* expressions appearing in "exprs"; return NULL if no match.
*
* "exprs" can be either a list of bare expression trees, or a list of
* TargetEntry nodes. Either way, it should contain Vars and possibly
* Aggrefs and WindowFuncs, which are matched to the corresponding elements
* of the EquivalenceClass's expressions.
*
* Unlike find_ec_member_matching_expr, there's no special provision here
* for binary-compatible relabeling. This is intentional: if we have to
* compute an expression in this way, setrefs.c is going to insist on exact
* matches of Vars to the source tlist.
*
* Child EC members are ignored unless they belong to given 'relids'.
* Also, non-parallel-safe expressions are ignored if 'require_parallel_safe'.
*
* Note: some callers pass root == NULL for notational reasons. This is OK
* when require_parallel_safe is false.
*/
EquivalenceMember *
find_computable_ec_member(PlannerInfo *root,
EquivalenceClass *ec,
List *exprs,
Relids relids,
bool require_parallel_safe)
{
ListCell *lc;
foreach(lc, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc);
List *exprvars;
ListCell *lc2;
/*
* We shouldn't be trying to sort by an equivalence class that
* contains a constant, so no need to consider such cases any further.
*/
if (em->em_is_const)
continue;
/*
* Ignore child members unless they belong to the requested rel.
*/
if (em->em_is_child &&
!bms_is_subset(em->em_relids, relids))
continue;
/*
* Match if all Vars and quasi-Vars are available in "exprs".
*/
exprvars = pull_var_clause((Node *) em->em_expr,
PVC_INCLUDE_AGGREGATES |
PVC_INCLUDE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
foreach(lc2, exprvars)
{
if (!is_exprlist_member(lfirst(lc2), exprs))
break;
}
list_free(exprvars);
if (lc2)
continue; /* we hit a non-available Var */
/*
* If requested, reject expressions that are not parallel-safe. We
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
!is_parallel_safe(root, (Node *) em->em_expr))
continue;
return em; /* found usable expression */
}
return NULL;
}
/*
* is_exprlist_member
* Subroutine for find_computable_ec_member: is "node" in "exprs"?
*
* Per the requirements of that function, "exprs" might or might not have
* TargetEntry superstructure.
*/
static bool
is_exprlist_member(Expr *node, List *exprs)
{
ListCell *lc;
foreach(lc, exprs)
{
Expr *expr = (Expr *) lfirst(lc);
if (expr && IsA(expr, TargetEntry))
expr = ((TargetEntry *) expr)->expr;
if (equal(node, expr))
return true;
}
return false;
}
/*
* relation_can_be_sorted_early
* Can this relation be sorted on this EC before the final output step?
*
* To succeed, we must find an EC member that prepare_sort_from_pathkeys knows
* how to sort on, given the rel's reltarget as input. There are also a few
* additional constraints based on the fact that the desired sort will be done
* "early", within the scan/join part of the plan. Also, non-parallel-safe
* expressions are ignored if 'require_parallel_safe'.
*
* At some point we might want to return the identified EquivalenceMember,
* but for now, callers only want to know if there is one.
*/
bool
relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, bool require_parallel_safe)
{
PathTarget *target = rel->reltarget;
EquivalenceMember *em;
ListCell *lc;
/*
* Reject volatile ECs immediately; such sorts must always be postponed.
*/
if (ec->ec_has_volatile)
return false;
/*
* Try to find an EM directly matching some reltarget member.
*/
foreach(lc, target->exprs)
{
Expr *targetexpr = (Expr *) lfirst(lc);
em = find_ec_member_matching_expr(ec, targetexpr, rel->relids);
if (!em)
continue;
/*
* Reject expressions involving set-returning functions, as those
* can't be computed early either. (Note: this test and the following
* one are effectively checking properties of targetexpr, so there's
* no point in asking whether some other EC member would be better.)
*/
if (expression_returns_set((Node *) em->em_expr))
continue;
/*
* If requested, reject expressions that are not parallel-safe. We
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
!is_parallel_safe(root, (Node *) em->em_expr))
continue;
return true;
}
/*
* Try to find an expression computable from the reltarget.
*/
em = find_computable_ec_member(root, ec, target->exprs, rel->relids,
require_parallel_safe);
if (!em)
return false;
/*
* Reject expressions involving set-returning functions, as those can't be
* computed early either. (There's no point in looking for another EC
* member in this case; since SRFs can't appear in WHERE, they cannot
* belong to multi-member ECs.)
*/
if (expression_returns_set((Node *) em->em_expr))
return false;
return true;
}
/*
* generate_base_implied_equalities
* Generate any restriction clauses that we can deduce from equivalence
* classes.
*
* When an EC contains pseudoconstants, our strategy is to generate
* "member = const1" clauses where const1 is the first constant member, for
* every other member (including other constants). If we are able to do this
* then we don't need any "var = var" comparisons because we've successfully
* constrained all the vars at their points of creation. If we fail to
* generate any of these clauses due to lack of cross-type operators, we fall
* back to the "ec_broken" strategy described below. (XXX if there are
* multiple constants of different types, it's possible that we might succeed
* in forming all the required clauses if we started from a different const
* member; but this seems a sufficiently hokey corner case to not be worth
* spending lots of cycles on.)
*
* For ECs that contain no pseudoconstants, we generate derived clauses
* "member1 = member2" for each pair of members belonging to the same base
* relation (actually, if there are more than two for the same base relation,
* we only need enough clauses to link each to each other). This provides
* the base case for the recursion: each row emitted by a base relation scan
* will constrain all computable members of the EC to be equal. As each
* join path is formed, we'll add additional derived clauses on-the-fly
* to maintain this invariant (see generate_join_implied_equalities).
*
* If the opfamilies used by the EC do not provide complete sets of cross-type
* equality operators, it is possible that we will fail to generate a clause
* that must be generated to maintain the invariant. (An example: given
* "WHERE a.x = b.y AND b.y = a.z", the scheme breaks down if we cannot
* generate "a.x = a.z" as a restriction clause for A.) In this case we mark
* the EC "ec_broken" and fall back to regurgitating its original source
* RestrictInfos at appropriate times. We do not try to retract any derived
* clauses already generated from the broken EC, so the resulting plan could
* be poor due to bad selectivity estimates caused by redundant clauses. But
* the correct solution to that is to fix the opfamilies ...
*
* Equality clauses derived by this function are passed off to
* process_implied_equality (in plan/initsplan.c) to be inserted into the
* restrictinfo datastructures. Note that this must be called after initial
* scanning of the quals and before Path construction begins.
*
* We make no attempt to avoid generating duplicate RestrictInfos here: we
* don't search ec_sources or ec_derives for matches. It doesn't really
* seem worth the trouble to do so.
*/
void
generate_base_implied_equalities(PlannerInfo *root)
{
int ec_index;
ListCell *lc;
/*
* At this point, we're done absorbing knowledge of equivalences in the
* query, so no further EC merging should happen, and ECs remaining in the
* eq_classes list can be considered canonical. (But note that it's still
* possible for new single-member ECs to be added through
* get_eclass_for_sort_expr().)
*/
root->ec_merging_done = true;
ec_index = 0;
foreach(lc, root->eq_classes)
{
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
bool can_generate_joinclause = false;
int i;
Assert(ec->ec_merged == NULL); /* else shouldn't be in list */
Assert(!ec->ec_broken); /* not yet anyway... */
/*
* Generate implied equalities that are restriction clauses.
* Single-member ECs won't generate any deductions, either here or at
* the join level.
*/
if (list_length(ec->ec_members) > 1)
{
if (ec->ec_has_const)
generate_base_implied_equalities_const(root, ec);
else
generate_base_implied_equalities_no_const(root, ec);
/* Recover if we failed to generate required derived clauses */
if (ec->ec_broken)
generate_base_implied_equalities_broken(root, ec);
/* Detect whether this EC might generate join clauses */
can_generate_joinclause =
(bms_membership(ec->ec_relids) == BMS_MULTIPLE);
}
/*
* Mark the base rels cited in each eclass (which should all exist by
* now) with the eq_classes indexes of all eclasses mentioning them.
* This will let us avoid searching in subsequent lookups. While
* we're at it, we can mark base rels that have pending eclass joins;
* this is a cheap version of has_relevant_eclass_joinclause().
*/
i = -1;
while ((i = bms_next_member(ec->ec_relids, i)) > 0)
{
RelOptInfo *rel = root->simple_rel_array[i];
if (rel == NULL) /* must be an outer join */
{
Assert(bms_is_member(i, root->outer_join_rels));
continue;
}
Assert(rel->reloptkind == RELOPT_BASEREL);
rel->eclass_indexes = bms_add_member(rel->eclass_indexes,
ec_index);
if (can_generate_joinclause)
rel->has_eclass_joins = true;
}
ec_index++;
}
}
/*
* generate_base_implied_equalities when EC contains pseudoconstant(s)
*/
static void
generate_base_implied_equalities_const(PlannerInfo *root,
EquivalenceClass *ec)
{
EquivalenceMember *const_em = NULL;
ListCell *lc;
/*
* In the trivial case where we just had one "var = const" clause, push
* the original clause back into the main planner machinery. There is
* nothing to be gained by doing it differently, and we save the effort to
* re-build and re-analyze an equality clause that will be exactly
* equivalent to the old one.
*/
if (list_length(ec->ec_members) == 2 &&
list_length(ec->ec_sources) == 1)
{
RestrictInfo *restrictinfo = (RestrictInfo *) linitial(ec->ec_sources);
distribute_restrictinfo_to_rels(root, restrictinfo);
return;
}
/*
* Find the constant member to use. We prefer an actual constant to
* pseudo-constants (such as Params), because the constraint exclusion
* machinery might be able to exclude relations on the basis of generated
* "var = const" equalities, but "var = param" won't work for that.
*/
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
if (cur_em->em_is_const)
{
const_em = cur_em;
if (IsA(cur_em->em_expr, Const))
break;
}
}
Assert(const_em != NULL);
/* Generate a derived equality against each other member */
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
Oid eq_op;
RestrictInfo *rinfo;
Assert(!cur_em->em_is_child); /* no children yet */
if (cur_em == const_em)
continue;
eq_op = select_equality_operator(ec,
cur_em->em_datatype,
const_em->em_datatype);
if (!OidIsValid(eq_op))
{
/* failed... */
ec->ec_broken = true;
break;
}
/*
* We use the constant's em_jdomain as qualscope, so that if the
* generated clause is variable-free (i.e, both EMs are consts) it
* will be enforced at the join domain level.
*/
rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
cur_em->em_expr, const_em->em_expr,
const_em->em_jdomain->jd_relids,
ec->ec_min_security,
cur_em->em_is_const);
/*
* If the clause didn't degenerate to a constant, fill in the correct
* markings for a mergejoinable clause, and save it in ec_derives. (We
* will not re-use such clauses directly, but selectivity estimation
* may consult the list later. Note that this use of ec_derives does
* not overlap with its use for join clauses, since we never generate
* join clauses from an ec_has_const eclass.)
*/
if (rinfo && rinfo->mergeopfamilies)
{
/* it's not redundant, so don't set parent_ec */
rinfo->left_ec = rinfo->right_ec = ec;
rinfo->left_em = cur_em;
rinfo->right_em = const_em;
ec->ec_derives = lappend(ec->ec_derives, rinfo);
}
}
}
/*
* generate_base_implied_equalities when EC contains no pseudoconstants
*/
static void
generate_base_implied_equalities_no_const(PlannerInfo *root,
EquivalenceClass *ec)
{
EquivalenceMember **prev_ems;
ListCell *lc;
/*
* We scan the EC members once and track the last-seen member for each
* base relation. When we see another member of the same base relation,
* we generate "prev_em = cur_em". This results in the minimum number of
* derived clauses, but it's possible that it will fail when a different
* ordering would succeed. XXX FIXME: use a UNION-FIND algorithm similar
* to the way we build merged ECs. (Use a list-of-lists for each rel.)
*/
prev_ems = (EquivalenceMember **)
palloc0(root->simple_rel_array_size * sizeof(EquivalenceMember *));
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
int relid;
Assert(!cur_em->em_is_child); /* no children yet */
if (!bms_get_singleton_member(cur_em->em_relids, &relid))
continue;
Assert(relid < root->simple_rel_array_size);
if (prev_ems[relid] != NULL)
{
EquivalenceMember *prev_em = prev_ems[relid];
Oid eq_op;
RestrictInfo *rinfo;
eq_op = select_equality_operator(ec,
prev_em->em_datatype,
cur_em->em_datatype);
if (!OidIsValid(eq_op))
{
/* failed... */
ec->ec_broken = true;
break;
}
/*
* The expressions aren't constants, so the passed qualscope will
* never be used to place the generated clause. We just need to
* be sure it covers both expressions, which em_relids should do.
*/
rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
prev_em->em_expr, cur_em->em_expr,
cur_em->em_relids,
ec->ec_min_security,
false);
/*
* If the clause didn't degenerate to a constant, fill in the
* correct markings for a mergejoinable clause. We don't put it
* in ec_derives however; we don't currently need to re-find such
* clauses, and we don't want to clutter that list with non-join
* clauses.
*/
if (rinfo && rinfo->mergeopfamilies)
{
/* it's not redundant, so don't set parent_ec */
rinfo->left_ec = rinfo->right_ec = ec;
rinfo->left_em = prev_em;
rinfo->right_em = cur_em;
}
}
prev_ems[relid] = cur_em;
}
pfree(prev_ems);
/*
* We also have to make sure that all the Vars used in the member clauses
* will be available at any join node we might try to reference them at.
* For the moment we force all the Vars to be available at all join nodes
* for this eclass. Perhaps this could be improved by doing some
* pre-analysis of which members we prefer to join, but it's no worse than
* what happened in the pre-8.3 code.
*/
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
List *vars = pull_var_clause((Node *) cur_em->em_expr,
PVC_RECURSE_AGGREGATES |
PVC_RECURSE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, ec->ec_relids);
list_free(vars);
}
}
/*
* generate_base_implied_equalities cleanup after failure
*
* What we must do here is push any zero- or one-relation source RestrictInfos
* of the EC back into the main restrictinfo datastructures. Multi-relation
* clauses will be regurgitated later by generate_join_implied_equalities().
* (We do it this way to maintain continuity with the case that ec_broken
* becomes set only after we've gone up a join level or two.) However, for
* an EC that contains constants, we can adopt a simpler strategy and just
* throw back all the source RestrictInfos immediately; that works because
* we know that such an EC can't become broken later. (This rule justifies
* ignoring ec_has_const ECs in generate_join_implied_equalities, even when
* they are broken.)
*/
static void
generate_base_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec)
{
ListCell *lc;
foreach(lc, ec->ec_sources)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
if (ec->ec_has_const ||
bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
distribute_restrictinfo_to_rels(root, restrictinfo);
}
}
/*
* generate_join_implied_equalities
* Generate any join clauses that we can deduce from equivalence classes.
*
* At a join node, we must enforce restriction clauses sufficient to ensure
* that all equivalence-class members computable at that node are equal.
* Since the set of clauses to enforce can vary depending on which subset
* relations are the inputs, we have to compute this afresh for each join
* relation pair. Hence a fresh List of RestrictInfo nodes is built and
* passed back on each call.
*
* In addition to its use at join nodes, this can be applied to generate
* eclass-based join clauses for use in a parameterized scan of a base rel.
* The reason for the asymmetry of specifying the inner rel as a RelOptInfo
* and the outer rel by Relids is that this usage occurs before we have
* built any join RelOptInfos.
*
* An annoying special case for parameterized scans is that the inner rel can
* be an appendrel child (an "other rel"). In this case we must generate
* appropriate clauses using child EC members. add_child_rel_equivalences
* must already have been done for the child rel.
*
* The results are sufficient for use in merge, hash, and plain nestloop join
* methods. We do not worry here about selecting clauses that are optimal
* for use in a parameterized indexscan. indxpath.c makes its own selections
* of clauses to use, and if the ones we pick here are redundant with those,
* the extras will be eliminated at createplan time, using the parent_ec
* markers that we provide (see is_redundant_derived_clause()).
*
* Because the same join clauses are likely to be needed multiple times as
* we consider different join paths, we avoid generating multiple copies:
* whenever we select a particular pair of EquivalenceMembers to join,
* we check to see if the pair matches any original clause (in ec_sources)
* or previously-built clause (in ec_derives). This saves memory and allows
* re-use of information cached in RestrictInfos. We also avoid generating
* commutative duplicates, i.e. if the algorithm selects "a.x = b.y" but
* we already have "b.y = a.x", we return the existing clause.
*
* If we are considering an outer join, sjinfo is the associated OJ info,
* otherwise it can be NULL.
*
* join_relids should always equal bms_union(outer_relids, inner_rel->relids)
* plus whatever add_outer_joins_to_relids() would add. We could simplify
* this function's API by computing it internally, but most callers have the
* value at hand anyway.
*/
List *
generate_join_implied_equalities(PlannerInfo *root,
Relids join_relids,
Relids outer_relids,
RelOptInfo *inner_rel,
SpecialJoinInfo *sjinfo)
{
List *result = NIL;
Relids inner_relids = inner_rel->relids;
Relids nominal_inner_relids;
Relids nominal_join_relids;
Bitmapset *matching_ecs;
int i;
/* If inner rel is a child, extra setup work is needed */
if (IS_OTHER_REL(inner_rel))
{
Assert(!bms_is_empty(inner_rel->top_parent_relids));
/* Fetch relid set for the topmost parent rel */
nominal_inner_relids = inner_rel->top_parent_relids;
/* ECs will be marked with the parent's relid, not the child's */
nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
nominal_join_relids = add_outer_joins_to_relids(root,
nominal_join_relids,
sjinfo,
NULL);
}
else
{
nominal_inner_relids = inner_relids;
nominal_join_relids = join_relids;
}
/*
* Examine all potentially-relevant eclasses.
*
* If we are considering an outer join, we must include "join" clauses
* that mention either input rel plus the outer join's relid; these
* represent post-join filter clauses that have to be applied at this
* join. We don't have infrastructure that would let us identify such
* eclasses cheaply, so just fall back to considering all eclasses
* mentioning anything in nominal_join_relids.
*
* At inner joins, we can be smarter: only consider eclasses mentioning
* both input rels.
*/
if (sjinfo && sjinfo->ojrelid != 0)
matching_ecs = get_eclass_indexes_for_relids(root, nominal_join_relids);
else
matching_ecs = get_common_eclass_indexes(root, nominal_inner_relids,
outer_relids);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
List *sublist = NIL;
/* ECs containing consts do not need any further enforcement */
if (ec->ec_has_const)
continue;
/* Single-member ECs won't generate any deductions */
if (list_length(ec->ec_members) <= 1)
continue;
/* Sanity check that this eclass overlaps the join */
Assert(bms_overlap(ec->ec_relids, nominal_join_relids));
if (!ec->ec_broken)
sublist = generate_join_implied_equalities_normal(root,
ec,
join_relids,
outer_relids,
inner_relids);
/* Recover if we failed to generate required derived clauses */
if (ec->ec_broken)
sublist = generate_join_implied_equalities_broken(root,
ec,
nominal_join_relids,
outer_relids,
nominal_inner_relids,
inner_rel);
result = list_concat(result, sublist);
}
return result;
}
/*
* generate_join_implied_equalities_for_ecs
* As above, but consider only the listed ECs.
*
* For the sole current caller, we can assume sjinfo == NULL, that is we are
* not interested in outer-join filter clauses. This might need to change
* in future.
*/
List *
generate_join_implied_equalities_for_ecs(PlannerInfo *root,
List *eclasses,
Relids join_relids,
Relids outer_relids,
RelOptInfo *inner_rel)
{
List *result = NIL;
Relids inner_relids = inner_rel->relids;
Relids nominal_inner_relids;
Relids nominal_join_relids;
ListCell *lc;
/* If inner rel is a child, extra setup work is needed */
if (IS_OTHER_REL(inner_rel))
{
Assert(!bms_is_empty(inner_rel->top_parent_relids));
/* Fetch relid set for the topmost parent rel */
nominal_inner_relids = inner_rel->top_parent_relids;
/* ECs will be marked with the parent's relid, not the child's */
nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
}
else
{
nominal_inner_relids = inner_relids;
nominal_join_relids = join_relids;
}
foreach(lc, eclasses)
{
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
List *sublist = NIL;
/* ECs containing consts do not need any further enforcement */
if (ec->ec_has_const)
continue;
/* Single-member ECs won't generate any deductions */
if (list_length(ec->ec_members) <= 1)
continue;
/* We can quickly ignore any that don't overlap the join, too */
if (!bms_overlap(ec->ec_relids, nominal_join_relids))
continue;
if (!ec->ec_broken)
sublist = generate_join_implied_equalities_normal(root,
ec,
join_relids,
outer_relids,
inner_relids);
/* Recover if we failed to generate required derived clauses */
if (ec->ec_broken)
sublist = generate_join_implied_equalities_broken(root,
ec,
nominal_join_relids,
outer_relids,
nominal_inner_relids,
inner_rel);
result = list_concat(result, sublist);
}
return result;
}
/*
* generate_join_implied_equalities for a still-valid EC
*/
static List *
generate_join_implied_equalities_normal(PlannerInfo *root,
EquivalenceClass *ec,
Relids join_relids,
Relids outer_relids,
Relids inner_relids)
{
List *result = NIL;
List *new_members = NIL;
List *outer_members = NIL;
List *inner_members = NIL;
ListCell *lc1;
/*
* First, scan the EC to identify member values that are computable at the
* outer rel, at the inner rel, or at this relation but not in either
* input rel. The outer-rel members should already be enforced equal,
* likewise for the inner-rel members. We'll need to create clauses to
* enforce that any newly computable members are all equal to each other
* as well as to at least one input member, plus enforce at least one
* outer-rel member equal to at least one inner-rel member.
*/
foreach(lc1, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
/*
* We don't need to check explicitly for child EC members. This test
* against join_relids will cause them to be ignored except when
* considering a child inner rel, which is what we want.
*/
if (!bms_is_subset(cur_em->em_relids, join_relids))
continue; /* not computable yet, or wrong child */
if (bms_is_subset(cur_em->em_relids, outer_relids))
outer_members = lappend(outer_members, cur_em);
else if (bms_is_subset(cur_em->em_relids, inner_relids))
inner_members = lappend(inner_members, cur_em);
else
new_members = lappend(new_members, cur_em);
}
/*
* First, select the joinclause if needed. We can equate any one outer
* member to any one inner member, but we have to find a datatype
* combination for which an opfamily member operator exists. If we have
* choices, we prefer simple Var members (possibly with RelabelType) since
* these are (a) cheapest to compute at runtime and (b) most likely to
* have useful statistics. Also, prefer operators that are also
* hashjoinable.
*/
if (outer_members && inner_members)
{
EquivalenceMember *best_outer_em = NULL;
EquivalenceMember *best_inner_em = NULL;
Oid best_eq_op = InvalidOid;
int best_score = -1;
RestrictInfo *rinfo;
foreach(lc1, outer_members)
{
EquivalenceMember *outer_em = (EquivalenceMember *) lfirst(lc1);
ListCell *lc2;
foreach(lc2, inner_members)
{
EquivalenceMember *inner_em = (EquivalenceMember *) lfirst(lc2);
Oid eq_op;
int score;
eq_op = select_equality_operator(ec,
outer_em->em_datatype,
inner_em->em_datatype);
if (!OidIsValid(eq_op))
continue;
score = 0;
if (IsA(outer_em->em_expr, Var) ||
(IsA(outer_em->em_expr, RelabelType) &&
IsA(((RelabelType *) outer_em->em_expr)->arg, Var)))
score++;
if (IsA(inner_em->em_expr, Var) ||
(IsA(inner_em->em_expr, RelabelType) &&
IsA(((RelabelType *) inner_em->em_expr)->arg, Var)))
score++;
if (op_hashjoinable(eq_op,
exprType((Node *) outer_em->em_expr)))
score++;
if (score > best_score)
{
best_outer_em = outer_em;
best_inner_em = inner_em;
best_eq_op = eq_op;
best_score = score;
if (best_score == 3)
break; /* no need to look further */
}
}
if (best_score == 3)
break; /* no need to look further */
}
if (best_score < 0)
{
/* failed... */
ec->ec_broken = true;
return NIL;
}
/*
* Create clause, setting parent_ec to mark it as redundant with other
* joinclauses
*/
rinfo = create_join_clause(root, ec, best_eq_op,
best_outer_em, best_inner_em,
ec);
result = lappend(result, rinfo);
}
/*
* Now deal with building restrictions for any expressions that involve
* Vars from both sides of the join. We have to equate all of these to
* each other as well as to at least one old member (if any).
*
* XXX as in generate_base_implied_equalities_no_const, we could be a lot
* smarter here to avoid unnecessary failures in cross-type situations.
* For now, use the same left-to-right method used there.
*/
if (new_members)
{
List *old_members = list_concat(outer_members, inner_members);
EquivalenceMember *prev_em = NULL;
RestrictInfo *rinfo;
/* For now, arbitrarily take the first old_member as the one to use */
if (old_members)
new_members = lappend(new_members, linitial(old_members));
foreach(lc1, new_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
if (prev_em != NULL)
{
Oid eq_op;
eq_op = select_equality_operator(ec,
prev_em->em_datatype,
cur_em->em_datatype);
if (!OidIsValid(eq_op))
{
/* failed... */
ec->ec_broken = true;
return NIL;
}
/* do NOT set parent_ec, this qual is not redundant! */
rinfo = create_join_clause(root, ec, eq_op,
prev_em, cur_em,
NULL);
result = lappend(result, rinfo);
}
prev_em = cur_em;
}
}
return result;
}
/*
* generate_join_implied_equalities cleanup after failure
*
* Return any original RestrictInfos that are enforceable at this join.
*
* In the case of a child inner relation, we have to translate the
* original RestrictInfos from parent to child Vars.
*/
static List *
generate_join_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec,
Relids nominal_join_relids,
Relids outer_relids,
Relids nominal_inner_relids,
RelOptInfo *inner_rel)
{
List *result = NIL;
ListCell *lc;
foreach(lc, ec->ec_sources)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
Relids clause_relids = restrictinfo->required_relids;
if (bms_is_subset(clause_relids, nominal_join_relids) &&
!bms_is_subset(clause_relids, outer_relids) &&
!bms_is_subset(clause_relids, nominal_inner_relids))
result = lappend(result, restrictinfo);
}
/*
* If we have to translate, just brute-force apply adjust_appendrel_attrs
* to all the RestrictInfos at once. This will result in returning
* RestrictInfos that are not listed in ec_derives, but there shouldn't be
* any duplication, and it's a sufficiently narrow corner case that we
* shouldn't sweat too much over it anyway.
*
* Since inner_rel might be an indirect descendant of the baserel
* mentioned in the ec_sources clauses, we have to be prepared to apply
* multiple levels of Var translation.
*/
if (IS_OTHER_REL(inner_rel) && result != NIL)
result = (List *) adjust_appendrel_attrs_multilevel(root,
(Node *) result,
inner_rel,
inner_rel->top_parent);
return result;
}
/*
* select_equality_operator
* Select a suitable equality operator for comparing two EC members
*
* Returns InvalidOid if no operator can be found for this datatype combination
*/
static Oid
select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype)
{
ListCell *lc;
foreach(lc, ec->ec_opfamilies)
{
Oid opfamily = lfirst_oid(lc);
Oid opno;
opno = get_opfamily_member(opfamily, lefttype, righttype,
BTEqualStrategyNumber);
if (!OidIsValid(opno))
continue;
/* If no barrier quals in query, don't worry about leaky operators */
if (ec->ec_max_security == 0)
return opno;
/* Otherwise, insist that selected operators be leakproof */
if (get_func_leakproof(get_opcode(opno)))
return opno;
}
return InvalidOid;
}
/*
* create_join_clause
* Find or make a RestrictInfo comparing the two given EC members
* with the given operator (or, possibly, its commutator, because
* the ordering of the operands in the result is not guaranteed).
*
* 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;
RestrictInfo *parent_rinfo = NULL;
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, and a commutator clause is acceptable.
*
* We used to verify that opno matches, but that seems redundant: even if
* it's not identical, it'd better have the same effects, or the operator
* families we're using are broken.
*/
foreach(lc, ec->ec_sources)
{
rinfo = (RestrictInfo *) lfirst(lc);
if (rinfo->left_em == leftem &&
rinfo->right_em == rightem &&
rinfo->parent_ec == parent_ec)
return rinfo;
if (rinfo->left_em == rightem &&
rinfo->right_em == leftem &&
rinfo->parent_ec == parent_ec)
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)
return rinfo;
if (rinfo->left_em == rightem &&
rinfo->right_em == leftem &&
rinfo->parent_ec == parent_ec)
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);
/*
* If either EM is a child, recursively create the corresponding
* parent-to-parent clause, so that we can duplicate its rinfo_serial.
*/
if (leftem->em_is_child || rightem->em_is_child)
{
EquivalenceMember *leftp = leftem->em_parent ? leftem->em_parent : leftem;
EquivalenceMember *rightp = rightem->em_parent ? rightem->em_parent : rightem;
parent_rinfo = create_join_clause(root, ec, opno,
leftp, rightp,
parent_ec);
}
rinfo = build_implied_join_equality(root,
opno,
ec->ec_collation,
leftem->em_expr,
rightem->em_expr,
bms_union(leftem->em_relids,
rightem->em_relids),
ec->ec_min_security);
/*
* If either EM is a child, force the clause's clause_relids to include
* the relid(s) of the child rel. In normal cases it would already, but
* not if we are considering appendrel child relations with pseudoconstant
* translated variables (i.e., UNION ALL sub-selects with constant output
* items). We must do this so that join_clause_is_movable_into() will
* think that the clause should be evaluated at the correct place.
*/
if (leftem->em_is_child)
rinfo->clause_relids = bms_add_members(rinfo->clause_relids,
leftem->em_relids);
if (rightem->em_is_child)
rinfo->clause_relids = bms_add_members(rinfo->clause_relids,
rightem->em_relids);
/* If it's a child clause, copy the parent's rinfo_serial */
if (parent_rinfo)
rinfo->rinfo_serial = parent_rinfo->rinfo_serial;
/* 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 must still put some
* clause into the regular processing, because otherwise the join will be
* seen as a clauseless join and avoided during join order searching.
* We handle this by generating a constant-TRUE clause that is marked with
* the same required_relids etc as the removed outer-join clause, thus
* making it a join clause between the correct relations.
*/
void
reconsider_outer_join_clauses(PlannerInfo *root)
{
bool found;
ListCell *cell;
/* Outer loop repeats until we find no more deductions */
do
{
found = false;
/* Process the LEFT JOIN clauses */
foreach(cell, root->left_join_clauses)
{
OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
if (reconsider_outer_join_clause(root, ojcinfo, true))
{
RestrictInfo *rinfo = ojcinfo->rinfo;
found = true;
/* remove it from the list */
root->left_join_clauses =
foreach_delete_current(root->left_join_clauses, cell);
/* throw back a dummy replacement clause (see notes above) */
rinfo = make_restrictinfo(root,
(Expr *) makeBoolConst(true, false),
rinfo->is_pushed_down,
rinfo->has_clone,
rinfo->is_clone,
false, /* pseudoconstant */
0, /* security_level */
rinfo->required_relids,
rinfo->incompatible_relids,
rinfo->outer_relids);
distribute_restrictinfo_to_rels(root, rinfo);
}
}
/* Process the RIGHT JOIN clauses */
foreach(cell, root->right_join_clauses)
{
OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
if (reconsider_outer_join_clause(root, ojcinfo, false))
{
RestrictInfo *rinfo = ojcinfo->rinfo;
found = true;
/* remove it from the list */
root->right_join_clauses =
foreach_delete_current(root->right_join_clauses, cell);
/* throw back a dummy replacement clause (see notes above) */
rinfo = make_restrictinfo(root,
(Expr *) makeBoolConst(true, false),
rinfo->is_pushed_down,
rinfo->has_clone,
rinfo->is_clone,
false, /* pseudoconstant */
0, /* security_level */
rinfo->required_relids,
rinfo->incompatible_relids,
rinfo->outer_relids);
distribute_restrictinfo_to_rels(root, rinfo);
}
}
/* Process the FULL JOIN clauses */
foreach(cell, root->full_join_clauses)
{
OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
if (reconsider_full_join_clause(root, ojcinfo))
{
RestrictInfo *rinfo = ojcinfo->rinfo;
found = true;
/* remove it from the list */
root->full_join_clauses =
foreach_delete_current(root->full_join_clauses, cell);
/* throw back a dummy replacement clause (see notes above) */
rinfo = make_restrictinfo(root,
(Expr *) makeBoolConst(true, false),
rinfo->is_pushed_down,
rinfo->has_clone,
rinfo->is_clone,
false, /* pseudoconstant */
0, /* security_level */
rinfo->required_relids,
rinfo->incompatible_relids,
rinfo->outer_relids);
distribute_restrictinfo_to_rels(root, rinfo);
}
}
} while (found);
/* Now, any remaining clauses have to be thrown back */
foreach(cell, root->left_join_clauses)
{
OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
distribute_restrictinfo_to_rels(root, ojcinfo->rinfo);
}
foreach(cell, root->right_join_clauses)
{
OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
distribute_restrictinfo_to_rels(root, ojcinfo->rinfo);
}
foreach(cell, root->full_join_clauses)
{
OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
distribute_restrictinfo_to_rels(root, ojcinfo->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, OuterJoinClauseInfo *ojcinfo,
bool outer_on_left)
{
RestrictInfo *rinfo = ojcinfo->rinfo;
SpecialJoinInfo *sjinfo = ojcinfo->sjinfo;
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;
/* 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;
JoinDomain *jdomain;
if (!cur_em->em_is_const)
continue; /* ignore non-const members */
eq_op = select_equality_operator(cur_ec,
inner_datatype,
cur_em->em_datatype);
if (!OidIsValid(eq_op))
continue; /* can't generate equality */
newrinfo = build_implied_join_equality(root,
eq_op,
cur_ec->ec_collation,
innervar,
cur_em->em_expr,
bms_copy(inner_relids),
cur_ec->ec_min_security);
/* This equality holds within the OJ's child JoinDomain */
jdomain = find_join_domain(root, sjinfo->syn_righthand);
if (process_equivalence(root, &newrinfo, jdomain))
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, OuterJoinClauseInfo *ojcinfo)
{
RestrictInfo *rinfo = ojcinfo->rinfo;
SpecialJoinInfo *sjinfo = ojcinfo->sjinfo;
Relids fjrelids = bms_make_singleton(sjinfo->ojrelid);
Expr *leftvar;
Expr *rightvar;
Oid opno,
collation,
left_type,
right_type;
Relids left_relids,
right_relids;
ListCell *lc1;
/* 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;
int coal_idx = -1;
/* Ignore EC unless it contains pseudoconstants */
if (!cur_ec->ec_has_const)
continue;
/* Never match to a volatile EC */
if (cur_ec->ec_has_volatile)
continue;
/* It has to match the outer-join clause as to semantics, too */
if (collation != cur_ec->ec_collation)
continue;
if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
continue;
/*
* Does it contain a COALESCE(leftvar, rightvar) construct?
*
* We can assume the COALESCE() inputs are in the same order as the
* join clause, since both were automatically generated in the cases
* we care about.
*
* XXX currently this may fail to match in cross-type cases because
* the COALESCE will contain typecast operations while the join clause
* may not (if there is a cross-type mergejoin operator available for
* the two column types). Is it OK to strip implicit coercions from
* the COALESCE arguments?
*/
match = false;
foreach(lc2, cur_ec->ec_members)
{
coal_em = (EquivalenceMember *) lfirst(lc2);
Assert(!coal_em->em_is_child); /* no children yet */
if (IsA(coal_em->em_expr, CoalesceExpr))
{
CoalesceExpr *cexpr = (CoalesceExpr *) coal_em->em_expr;
Node *cfirst;
Node *csecond;
if (list_length(cexpr->args) != 2)
continue;
cfirst = (Node *) linitial(cexpr->args);
csecond = (Node *) lsecond(cexpr->args);
/*
* The COALESCE arguments will be marked as possibly nulled by
* the full join, while we wish to generate clauses that apply
* to the join's inputs. So we must strip the join from the
* nullingrels fields of cfirst/csecond before comparing them
* to leftvar/rightvar. (Perhaps with a less hokey
* representation for FULL JOIN USING output columns, this
* wouldn't be needed?)
*/
cfirst = remove_nulling_relids(cfirst, fjrelids, NULL);
csecond = remove_nulling_relids(csecond, fjrelids, NULL);
if (equal(leftvar, cfirst) && equal(rightvar, csecond))
{
coal_idx = foreach_current_index(lc2);
match = true;
break;
}
}
}
if (!match)
continue; /* no match, so ignore this EC */
/*
* Yes it does! Try to generate clauses LEFTVAR = CONSTANT and
* RIGHTVAR = CONSTANT for each CONSTANT in the EC. Note that we must
* succeed with at least one constant for each var before we can
* decide to throw away the outer-join clause.
*/
matchleft = matchright = false;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
Oid eq_op;
RestrictInfo *newrinfo;
JoinDomain *jdomain;
if (!cur_em->em_is_const)
continue; /* ignore non-const members */
eq_op = select_equality_operator(cur_ec,
left_type,
cur_em->em_datatype);
if (OidIsValid(eq_op))
{
newrinfo = build_implied_join_equality(root,
eq_op,
cur_ec->ec_collation,
leftvar,
cur_em->em_expr,
bms_copy(left_relids),
cur_ec->ec_min_security);
/* This equality holds within the lefthand child JoinDomain */
jdomain = find_join_domain(root, sjinfo->syn_lefthand);
if (process_equivalence(root, &newrinfo, jdomain))
matchleft = true;
}
eq_op = select_equality_operator(cur_ec,
right_type,
cur_em->em_datatype);
if (OidIsValid(eq_op))
{
newrinfo = build_implied_join_equality(root,
eq_op,
cur_ec->ec_collation,
rightvar,
cur_em->em_expr,
bms_copy(right_relids),
cur_ec->ec_min_security);
/* This equality holds within the righthand child JoinDomain */
jdomain = find_join_domain(root, sjinfo->syn_righthand);
if (process_equivalence(root, &newrinfo, jdomain))
matchright = true;
}
}
/*
* If we were able to equate both vars to constants, we're done, and
* we can throw away the full-join clause as redundant. Moreover, we
* can remove the COALESCE entry from the EC, since the added
* restrictions ensure it will always have the expected value. (We
* don't bother trying to update ec_relids or ec_sources.)
*/
if (matchleft && matchright)
{
cur_ec->ec_members = list_delete_nth_cell(cur_ec->ec_members, coal_idx);
return true;
}
/*
* Otherwise, fall out of the search loop, since we know the COALESCE
* appears in at most one EC (XXX might stop being true if we allow
* stripping of coercions above?)
*/
break;
}
return false; /* failed to make any deduction */
}
/*
* find_join_domain
* Find the highest JoinDomain enclosed within the given relid set.
*
* (We could avoid this search at the cost of complicating APIs elsewhere,
* which doesn't seem worth it.)
*/
static JoinDomain *
find_join_domain(PlannerInfo *root, Relids relids)
{
ListCell *lc;
foreach(lc, root->join_domains)
{
JoinDomain *jdomain = (JoinDomain *) lfirst(lc);
if (bms_is_subset(jdomain->jd_relids, relids))
return jdomain;
}
elog(ERROR, "failed to find appropriate JoinDomain");
return NULL; /* keep compiler quiet */
}
/*
* exprs_known_equal
* Detect whether two expressions are known equal due to equivalence
* relationships.
*
* Actually, this only shows that the expressions are equal according
* to some opfamily's notion of equality --- but we only use it for
* selectivity estimation, so a fuzzy idea of equality is OK.
*
* Note: does not bother to check for "equal(item1, item2)"; caller must
* check that case if it's possible to pass identical items.
*/
bool
exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2)
{
ListCell *lc1;
foreach(lc1, root->eq_classes)
{
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
bool item1member = false;
bool item2member = false;
ListCell *lc2;
/* Never match to a volatile EC */
if (ec->ec_has_volatile)
continue;
foreach(lc2, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
if (em->em_is_child)
continue; /* ignore children here */
if (equal(item1, em->em_expr))
item1member = true;
else if (equal(item2, em->em_expr))
item2member = true;
/* Exit as soon as equality is proven */
if (item1member && item2member)
return true;
}
}
return false;
}
/*
* match_eclasses_to_foreign_key_col
* See whether a foreign key column match is proven by any eclass.
*
* If the referenced and referencing Vars of the fkey's colno'th column are
* known equal due to any eclass, return that eclass; otherwise return NULL.
* (In principle there might be more than one matching eclass if multiple
* collations are involved, but since collation doesn't matter for equality,
* we ignore that fine point here.) This is much like exprs_known_equal,
* except that we insist on the comparison operator matching the eclass, so
* that the result is definite not approximate.
*
* On success, we also set fkinfo->eclass[colno] to the matching eclass,
* and set fkinfo->fk_eclass_member[colno] to the eclass member for the
* referencing Var.
*/
EquivalenceClass *
match_eclasses_to_foreign_key_col(PlannerInfo *root,
ForeignKeyOptInfo *fkinfo,
int colno)
{
Index var1varno = fkinfo->con_relid;
AttrNumber var1attno = fkinfo->conkey[colno];
Index var2varno = fkinfo->ref_relid;
AttrNumber var2attno = fkinfo->confkey[colno];
Oid eqop = fkinfo->conpfeqop[colno];
RelOptInfo *rel1 = root->simple_rel_array[var1varno];
RelOptInfo *rel2 = root->simple_rel_array[var2varno];
List *opfamilies = NIL; /* compute only if needed */
Bitmapset *matching_ecs;
int i;
/* Consider only eclasses mentioning both relations */
Assert(root->ec_merging_done);
Assert(IS_SIMPLE_REL(rel1));
Assert(IS_SIMPLE_REL(rel2));
matching_ecs = bms_intersect(rel1->eclass_indexes,
rel2->eclass_indexes);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
i);
EquivalenceMember *item1_em = NULL;
EquivalenceMember *item2_em = NULL;
ListCell *lc2;
/* Never match to a volatile EC */
if (ec->ec_has_volatile)
continue;
/* Note: it seems okay to match to "broken" eclasses here */
foreach(lc2, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
Var *var;
if (em->em_is_child)
continue; /* ignore children here */
/* EM must be a Var, possibly with RelabelType */
var = (Var *) em->em_expr;
while (var && IsA(var, RelabelType))
var = (Var *) ((RelabelType *) var)->arg;
if (!(var && IsA(var, Var)))
continue;
/* Match? */
if (var->varno == var1varno && var->varattno == var1attno)
item1_em = em;
else if (var->varno == var2varno && var->varattno == var2attno)
item2_em = em;
/* Have we found both PK and FK column in this EC? */
if (item1_em && item2_em)
{
/*
* Succeed if eqop matches EC's opfamilies. We could test
* this before scanning the members, but it's probably cheaper
* to test for member matches first.
*/
if (opfamilies == NIL) /* compute if we didn't already */
opfamilies = get_mergejoin_opfamilies(eqop);
if (equal(opfamilies, ec->ec_opfamilies))
{
fkinfo->eclass[colno] = ec;
fkinfo->fk_eclass_member[colno] = item2_em;
return ec;
}
/* Otherwise, done with this EC, move on to the next */
break;
}
}
}
return NULL;
}
/*
* find_derived_clause_for_ec_member
* Search for a previously-derived clause mentioning the given EM.
*
* The eclass should be an ec_has_const EC, of which the EM is a non-const
* member. This should ensure there is just one derived clause mentioning
* the EM (and equating it to a constant).
* Returns NULL if no such clause can be found.
*/
RestrictInfo *
find_derived_clause_for_ec_member(EquivalenceClass *ec,
EquivalenceMember *em)
{
ListCell *lc;
Assert(ec->ec_has_const);
Assert(!em->em_is_const);
foreach(lc, ec->ec_derives)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
/*
* generate_base_implied_equalities_const will have put non-const
* members on the left side of derived clauses.
*/
if (rinfo->left_em == em)
return rinfo;
}
return NULL;
}
/*
* add_child_rel_equivalences
* Search for EC members that reference the root parent of child_rel, and
* add transformed members referencing the child_rel.
*
* Note that this function won't be called at all unless we have at least some
* reason to believe that the EC members it generates will be useful.
*
* parent_rel and child_rel could be derived from appinfo, but since the
* caller has already computed them, we might as well just pass them in.
*
* The passed-in AppendRelInfo is not used when the parent_rel is not a
* top-level baserel, since it shows the mapping from the parent_rel but
* we need to translate EC expressions that refer to the top-level parent.
* Using it is faster than using adjust_appendrel_attrs_multilevel(), though,
* so we prefer it when we can.
*/
void
add_child_rel_equivalences(PlannerInfo *root,
AppendRelInfo *appinfo,
RelOptInfo *parent_rel,
RelOptInfo *child_rel)
{
Relids top_parent_relids = child_rel->top_parent_relids;
Relids child_relids = child_rel->relids;
int i;
/*
* EC merging should be complete already, so we can use the parent rel's
* eclass_indexes to avoid searching all of root->eq_classes.
*/
Assert(root->ec_merging_done);
Assert(IS_SIMPLE_REL(parent_rel));
i = -1;
while ((i = bms_next_member(parent_rel->eclass_indexes, i)) >= 0)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
int num_members;
/*
* If this EC contains a volatile expression, then generating child
* EMs would be downright dangerous, so skip it. We rely on a
* volatile EC having only one EM.
*/
if (cur_ec->ec_has_volatile)
continue;
/* Sanity check eclass_indexes only contain ECs for parent_rel */
Assert(bms_is_subset(top_parent_relids, cur_ec->ec_relids));
/*
* We don't use foreach() here because there's no point in scanning
* newly-added child members, so we can stop after the last
* pre-existing EC member.
*/
num_members = list_length(cur_ec->ec_members);
for (int pos = 0; pos < num_members; pos++)
{
EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
if (cur_em->em_is_const)
continue; /* ignore consts here */
/*
* We consider only original EC members here, not
* already-transformed child members. Otherwise, if some original
* member expression references more than one appendrel, we'd get
* an O(N^2) explosion of useless derived expressions for
* combinations of children. (But add_child_join_rel_equivalences
* may add targeted combinations for partitionwise-join purposes.)
*/
if (cur_em->em_is_child)
continue; /* ignore children here */
/*
* Consider only members that reference and can be computed at
* child's topmost parent rel. In particular we want to exclude
* parent-rel Vars that have nonempty varnullingrels. Translating
* those might fail, if the transformed expression wouldn't be a
* simple Var; and in any case it wouldn't produce a member that
* has any use in creating plans for the child rel.
*/
if (bms_is_subset(cur_em->em_relids, top_parent_relids) &&
!bms_is_empty(cur_em->em_relids))
{
/* OK, generate transformed child version */
Expr *child_expr;
Relids new_relids;
if (parent_rel->reloptkind == RELOPT_BASEREL)
{
/* Simple single-level transformation */
child_expr = (Expr *)
adjust_appendrel_attrs(root,
(Node *) cur_em->em_expr,
1, &appinfo);
}
else
{
/* Must do multi-level transformation */
child_expr = (Expr *)
adjust_appendrel_attrs_multilevel(root,
(Node *) cur_em->em_expr,
child_rel,
child_rel->top_parent);
}
/*
* Transform em_relids to match. Note we do *not* do
* pull_varnos(child_expr) here, as for example the
* transformation might have substituted a constant, but we
* don't want the child member to be marked as constant.
*/
new_relids = bms_difference(cur_em->em_relids,
top_parent_relids);
new_relids = bms_add_members(new_relids, child_relids);
(void) add_eq_member(cur_ec, child_expr, new_relids,
cur_em->em_jdomain,
cur_em, cur_em->em_datatype);
/* Record this EC index for the child rel */
child_rel->eclass_indexes = bms_add_member(child_rel->eclass_indexes, i);
}
}
}
}
/*
* add_child_join_rel_equivalences
* Like add_child_rel_equivalences(), but for joinrels
*
* Here we find the ECs relevant to the top parent joinrel and add transformed
* member expressions that refer to this child joinrel.
*
* Note that this function won't be called at all unless we have at least some
* reason to believe that the EC members it generates will be useful.
*/
void
add_child_join_rel_equivalences(PlannerInfo *root,
int nappinfos, AppendRelInfo **appinfos,
RelOptInfo *parent_joinrel,
RelOptInfo *child_joinrel)
{
Relids top_parent_relids = child_joinrel->top_parent_relids;
Relids child_relids = child_joinrel->relids;
Bitmapset *matching_ecs;
MemoryContext oldcontext;
int i;
Assert(IS_JOIN_REL(child_joinrel) && IS_JOIN_REL(parent_joinrel));
/* We need consider only ECs that mention the parent joinrel */
matching_ecs = get_eclass_indexes_for_relids(root, top_parent_relids);
/*
* If we're being called during GEQO join planning, we still have to
* create any new EC members in the main planner context, to avoid having
* a corrupt EC data structure after the GEQO context is reset. This is
* problematic since we'll leak memory across repeated GEQO cycles. For
* now, though, bloat is better than crash. If it becomes a real issue
* we'll have to do something to avoid generating duplicate EC members.
*/
oldcontext = MemoryContextSwitchTo(root->planner_cxt);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
int num_members;
/*
* If this EC contains a volatile expression, then generating child
* EMs would be downright dangerous, so skip it. We rely on a
* volatile EC having only one EM.
*/
if (cur_ec->ec_has_volatile)
continue;
/* Sanity check on get_eclass_indexes_for_relids result */
Assert(bms_overlap(top_parent_relids, cur_ec->ec_relids));
/*
* We don't use foreach() here because there's no point in scanning
* newly-added child members, so we can stop after the last
* pre-existing EC member.
*/
num_members = list_length(cur_ec->ec_members);
for (int pos = 0; pos < num_members; pos++)
{
EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
if (cur_em->em_is_const)
continue; /* ignore consts here */
/*
* We consider only original EC members here, not
* already-transformed child members.
*/
if (cur_em->em_is_child)
continue; /* ignore children here */
/*
* We may ignore expressions that reference a single baserel,
* because add_child_rel_equivalences should have handled them.
*/
if (bms_membership(cur_em->em_relids) != BMS_MULTIPLE)
continue;
/* Does this member reference child's topmost parent rel? */
if (bms_overlap(cur_em->em_relids, top_parent_relids))
{
/* Yes, generate transformed child version */
Expr *child_expr;
Relids new_relids;
if (parent_joinrel->reloptkind == RELOPT_JOINREL)
{
/* Simple single-level transformation */
child_expr = (Expr *)
adjust_appendrel_attrs(root,
(Node *) cur_em->em_expr,
nappinfos, appinfos);
}
else
{
/* Must do multi-level transformation */
Assert(parent_joinrel->reloptkind == RELOPT_OTHER_JOINREL);
child_expr = (Expr *)
adjust_appendrel_attrs_multilevel(root,
(Node *) cur_em->em_expr,
child_joinrel,
child_joinrel->top_parent);
}
/*
* Transform em_relids to match. Note we do *not* do
* pull_varnos(child_expr) here, as for example the
* transformation might have substituted a constant, but we
* don't want the child member to be marked as constant.
*/
new_relids = bms_difference(cur_em->em_relids,
top_parent_relids);
new_relids = bms_add_members(new_relids, child_relids);
(void) add_eq_member(cur_ec, child_expr, new_relids,
cur_em->em_jdomain,
cur_em, cur_em->em_datatype);
}
}
}
MemoryContextSwitchTo(oldcontext);
}
/*
* add_setop_child_rel_equivalences
* Add equivalence members for each non-resjunk target in 'child_tlist'
* to the EquivalenceClass in the corresponding setop_pathkey's pk_class.
*
* 'root' is the PlannerInfo belonging to the top-level set operation.
* 'child_rel' is the RelOptInfo of the child relation we're adding
* EquivalenceMembers for.
* 'child_tlist' is the target list for the setop child relation. The target
* list expressions are what we add as EquivalenceMembers.
* 'setop_pathkeys' is a list of PathKeys which must contain an entry for each
* non-resjunk target in 'child_tlist'.
*/
void
add_setop_child_rel_equivalences(PlannerInfo *root, RelOptInfo *child_rel,
List *child_tlist, List *setop_pathkeys)
{
ListCell *lc;
ListCell *lc2 = list_head(setop_pathkeys);
foreach(lc, child_tlist)
{
TargetEntry *tle = lfirst_node(TargetEntry, lc);
EquivalenceMember *parent_em;
PathKey *pk;
if (tle->resjunk)
continue;
if (lc2 == NULL)
elog(ERROR, "too few pathkeys for set operation");
pk = lfirst_node(PathKey, lc2);
parent_em = linitial(pk->pk_eclass->ec_members);
/*
* We can safely pass the parent member as the first member in the
* ec_members list as this is added first in generate_union_paths,
* likewise, the JoinDomain can be that of the initial member of the
* Pathkey's EquivalenceClass.
*/
add_eq_member(pk->pk_eclass,
tle->expr,
child_rel->relids,
parent_em->em_jdomain,
parent_em,
exprType((Node *) tle->expr));
lc2 = lnext(setop_pathkeys, lc2);
}
/*
* transformSetOperationStmt() ensures that the targetlist never contains
* any resjunk columns, so all eclasses that exist in 'root' must have
* received a new member in the loop above. Add them to the child_rel's
* eclass_indexes.
*/
child_rel->eclass_indexes = bms_add_range(child_rel->eclass_indexes, 0,
list_length(root->eq_classes) - 1);
}
/*
* generate_implied_equalities_for_column
* Create EC-derived joinclauses usable with a specific column.
*
* This is used by indxpath.c to extract potentially indexable joinclauses
* from ECs, and can be used by foreign data wrappers for similar purposes.
* We assume that only expressions in Vars of a single table are of interest,
* but the caller provides a callback function to identify exactly which
* such expressions it would like to know about.
*
* We assume that any given table/index column could appear in only one EC.
* (This should be true in all but the most pathological cases, and if it
* isn't, we stop on the first match anyway.) Therefore, what we return
* is a redundant list of clauses equating the table/index column to each of
* the other-relation values it is known to be equal to. Any one of
* these clauses can be used to create a parameterized path, and there
* is no value in using more than one. (But it *is* worthwhile to create
* a separate parameterized path for each one, since that leads to different
* join orders.)
*
* The caller can pass a Relids set of rels we aren't interested in joining
* to, so as to save the work of creating useless clauses.
*/
List *
generate_implied_equalities_for_column(PlannerInfo *root,
RelOptInfo *rel,
ec_matches_callback_type callback,
void *callback_arg,
Relids prohibited_rels)
{
List *result = NIL;
bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
Relids parent_relids;
int i;
/* Should be OK to rely on eclass_indexes */
Assert(root->ec_merging_done);
/* Indexes are available only on base or "other" member relations. */
Assert(IS_SIMPLE_REL(rel));
/* If it's a child rel, we'll need to know what its parent(s) are */
if (is_child_rel)
parent_relids = find_childrel_parents(root, rel);
else
parent_relids = NULL; /* not used, but keep compiler quiet */
i = -1;
while ((i = bms_next_member(rel->eclass_indexes, i)) >= 0)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
EquivalenceMember *cur_em;
ListCell *lc2;
/* Sanity check eclass_indexes only contain ECs for rel */
Assert(is_child_rel || bms_is_subset(rel->relids, cur_ec->ec_relids));
/*
* Won't generate joinclauses if const or single-member (the latter
* test covers the volatile case too)
*/
if (cur_ec->ec_has_const || list_length(cur_ec->ec_members) <= 1)
continue;
/*
* Scan members, looking for a match to the target column. Note that
* child EC members are considered, but only when they belong to the
* target relation. (Unlike regular members, the same expression
* could be a child member of more than one EC. Therefore, it's
* potentially order-dependent which EC a child relation's target
* column gets matched to. This is annoying but it only happens in
* corner cases, so for now we live with just reporting the first
* match. See also get_eclass_for_sort_expr.)
*/
cur_em = NULL;
foreach(lc2, cur_ec->ec_members)
{
cur_em = (EquivalenceMember *) lfirst(lc2);
if (bms_equal(cur_em->em_relids, rel->relids) &&
callback(root, rel, cur_ec, cur_em, callback_arg))
break;
cur_em = NULL;
}
if (!cur_em)
continue;
/*
* Found our match. Scan the other EC members and attempt to generate
* joinclauses.
*/
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *other_em = (EquivalenceMember *) lfirst(lc2);
Oid eq_op;
RestrictInfo *rinfo;
if (other_em->em_is_child)
continue; /* ignore children here */
/* Make sure it'll be a join to a different rel */
if (other_em == cur_em ||
bms_overlap(other_em->em_relids, rel->relids))
continue;
/* Forget it if caller doesn't want joins to this rel */
if (bms_overlap(other_em->em_relids, prohibited_rels))
continue;
/*
* Also, if this is a child rel, avoid generating a useless join
* to its parent rel(s).
*/
if (is_child_rel &&
bms_overlap(parent_relids, other_em->em_relids))
continue;
eq_op = select_equality_operator(cur_ec,
cur_em->em_datatype,
other_em->em_datatype);
if (!OidIsValid(eq_op))
continue;
/* set parent_ec to mark as redundant with other joinclauses */
rinfo = create_join_clause(root, cur_ec, eq_op,
cur_em, other_em,
cur_ec);
result = lappend(result, rinfo);
}
/*
* If somehow we failed to create any join clauses, we might as well
* keep scanning the ECs for another match. But if we did make any,
* we're done, because we don't want to return non-redundant clauses.
*/
if (result)
break;
}
return result;
}
/*
* have_relevant_eclass_joinclause
* Detect whether there is an EquivalenceClass that could produce
* a joinclause involving the two given relations.
*
* This is essentially a very cut-down version of
* generate_join_implied_equalities(). Note it's OK to occasionally say "yes"
* incorrectly. Hence we don't bother with details like whether the lack of a
* cross-type operator might prevent the clause from actually being generated.
* False negatives are not always fatal either: they will discourage, but not
* completely prevent, investigation of particular join pathways.
*/
bool
have_relevant_eclass_joinclause(PlannerInfo *root,
RelOptInfo *rel1, RelOptInfo *rel2)
{
Bitmapset *matching_ecs;
int i;
/*
* Examine only eclasses mentioning both rel1 and rel2.
*
* Note that we do not consider the possibility of an eclass generating
* "join" clauses that mention just one of the rels plus an outer join
* that could be formed from them. Although such clauses must be
* correctly enforced when we form the outer join, they don't seem like
* sufficient reason to prioritize this join over other ones. The join
* ordering rules will force the join to be made when necessary.
*/
matching_ecs = get_common_eclass_indexes(root, rel1->relids,
rel2->relids);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
i);
/*
* Sanity check that get_common_eclass_indexes gave only ECs
* containing both rels.
*/
Assert(bms_overlap(rel1->relids, ec->ec_relids));
Assert(bms_overlap(rel2->relids, ec->ec_relids));
/*
* Won't generate joinclauses if single-member (this test covers the
* volatile case too)
*/
if (list_length(ec->ec_members) <= 1)
continue;
/*
* We do not need to examine the individual members of the EC, because
* all that we care about is whether each rel overlaps the relids of
* at least one member, and get_common_eclass_indexes() and the single
* member check above are sufficient to prove that. (As with
* have_relevant_joinclause(), it is not necessary that the EC be able
* to form a joinclause relating exactly the two given rels, only that
* it be able to form a joinclause mentioning both, and this will
* surely be true if both of them overlap ec_relids.)
*
* Note we don't test ec_broken; if we did, we'd need a separate code
* path to look through ec_sources. Checking the membership anyway is
* OK as a possibly-overoptimistic heuristic.
*
* We don't test ec_has_const either, even though a const eclass won't
* generate real join clauses. This is because if we had "WHERE a.x =
* b.y and a.x = 42", it is worth considering a join between a and b,
* since the join result is likely to be small even though it'll end
* up being an unqualified nestloop.
*/
return true;
}
return false;
}
/*
* has_relevant_eclass_joinclause
* Detect whether there is an EquivalenceClass that could produce
* a joinclause involving the given relation and anything else.
*
* This is the same as have_relevant_eclass_joinclause with the other rel
* implicitly defined as "everything else in the query".
*/
bool
has_relevant_eclass_joinclause(PlannerInfo *root, RelOptInfo *rel1)
{
Bitmapset *matched_ecs;
int i;
/* Examine only eclasses mentioning rel1 */
matched_ecs = get_eclass_indexes_for_relids(root, rel1->relids);
i = -1;
while ((i = bms_next_member(matched_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
i);
/*
* Won't generate joinclauses if single-member (this test covers the
* volatile case too)
*/
if (list_length(ec->ec_members) <= 1)
continue;
/*
* Per the comment in have_relevant_eclass_joinclause, it's sufficient
* to find an EC that mentions both this rel and some other rel.
*/
if (!bms_is_subset(ec->ec_relids, rel1->relids))
return true;
}
return false;
}
/*
* eclass_useful_for_merging
* Detect whether the EC could produce any mergejoinable join clauses
* against the specified relation.
*
* This is just a heuristic test and doesn't have to be exact; it's better
* to say "yes" incorrectly than "no". Hence we don't bother with details
* like whether the lack of a cross-type operator might prevent the clause
* from actually being generated.
*/
bool
eclass_useful_for_merging(PlannerInfo *root,
EquivalenceClass *eclass,
RelOptInfo *rel)
{
Relids relids;
ListCell *lc;
Assert(!eclass->ec_merged);
/*
* Won't generate joinclauses if const or single-member (the latter test
* covers the volatile case too)
*/
if (eclass->ec_has_const || list_length(eclass->ec_members) <= 1)
return false;
/*
* Note we don't test ec_broken; if we did, we'd need a separate code path
* to look through ec_sources. Checking the members anyway is OK as a
* possibly-overoptimistic heuristic.
*/
/* If specified rel is a child, we must consider the topmost parent rel */
if (IS_OTHER_REL(rel))
{
Assert(!bms_is_empty(rel->top_parent_relids));
relids = rel->top_parent_relids;
}
else
relids = rel->relids;
/* If rel already includes all members of eclass, no point in searching */
if (bms_is_subset(eclass->ec_relids, relids))
return false;
/* To join, we need a member not in the given rel */
foreach(lc, eclass->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
if (cur_em->em_is_child)
continue; /* ignore children here */
if (!bms_overlap(cur_em->em_relids, relids))
return true;
}
return false;
}
/*
* is_redundant_derived_clause
* Test whether rinfo is derived from same EC as any clause in clauselist;
* if so, it can be presumed to represent a condition that's redundant
* with that member of the list.
*/
bool
is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist)
{
EquivalenceClass *parent_ec = rinfo->parent_ec;
ListCell *lc;
/* Fail if it's not a potentially-redundant clause from some EC */
if (parent_ec == NULL)
return false;
foreach(lc, clauselist)
{
RestrictInfo *otherrinfo = (RestrictInfo *) lfirst(lc);
if (otherrinfo->parent_ec == parent_ec)
return true;
}
return false;
}
/*
* is_redundant_with_indexclauses
* Test whether rinfo is redundant with any clause in the IndexClause
* list. Here, for convenience, we test both simple identity and
* whether it is derived from the same EC as any member of the list.
*/
bool
is_redundant_with_indexclauses(RestrictInfo *rinfo, List *indexclauses)
{
EquivalenceClass *parent_ec = rinfo->parent_ec;
ListCell *lc;
foreach(lc, indexclauses)
{
IndexClause *iclause = lfirst_node(IndexClause, lc);
RestrictInfo *otherrinfo = iclause->rinfo;
/* If indexclause is lossy, it won't enforce the condition exactly */
if (iclause->lossy)
continue;
/* Match if it's same clause (pointer equality should be enough) */
if (rinfo == otherrinfo)
return true;
/* Match if derived from same EC */
if (parent_ec && otherrinfo->parent_ec == parent_ec)
return true;
/*
* No need to look at the derived clauses in iclause->indexquals; they
* couldn't match if the parent clause didn't.
*/
}
return false;
}
/*
* get_eclass_indexes_for_relids
* Build and return a Bitmapset containing the indexes into root's
* eq_classes list for all eclasses that mention any of these relids
*/
static Bitmapset *
get_eclass_indexes_for_relids(PlannerInfo *root, Relids relids)
{
Bitmapset *ec_indexes = NULL;
int i = -1;
/* Should be OK to rely on eclass_indexes */
Assert(root->ec_merging_done);
while ((i = bms_next_member(relids, i)) > 0)
{
RelOptInfo *rel = root->simple_rel_array[i];
if (rel == NULL) /* must be an outer join */
{
Assert(bms_is_member(i, root->outer_join_rels));
continue;
}
ec_indexes = bms_add_members(ec_indexes, rel->eclass_indexes);
}
return ec_indexes;
}
/*
* get_common_eclass_indexes
* Build and return a Bitmapset containing the indexes into root's
* eq_classes list for all eclasses that mention rels in both
* relids1 and relids2.
*/
static Bitmapset *
get_common_eclass_indexes(PlannerInfo *root, Relids relids1, Relids relids2)
{
Bitmapset *rel1ecs;
Bitmapset *rel2ecs;
int relid;
rel1ecs = get_eclass_indexes_for_relids(root, relids1);
/*
* We can get away with just using the relation's eclass_indexes directly
* when relids2 is a singleton set.
*/
if (bms_get_singleton_member(relids2, &relid))
rel2ecs = root->simple_rel_array[relid]->eclass_indexes;
else
rel2ecs = get_eclass_indexes_for_relids(root, relids2);
/* Calculate and return the common EC indexes, recycling the left input. */
return bms_int_members(rel1ecs, rel2ecs);
}
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