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apache/cloudberry/refs/heads/reshke-patch-1/./src/backend/optimizer/path/equivclass.c
blob: 547b25509172dfbb1a04dd571820756f4966c808 [file] [log] [blame]
/*-------------------------------------------------------------------------
*
* equivclass.c
* Routines for managing EquivalenceClasses
*
* See src/backend/optimizer/README for discussion of EquivalenceClasses.
*
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/optimizer/path/equivclass.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include "access/stratnum.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/appendinfo.h"
#include "optimizer/clauses.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/restrictinfo.h"
#include "utils/lsyscache.h"
static EquivalenceMember *add_eq_member(EquivalenceClass *ec,
Expr *expr, Relids relids, Relids nullable_relids,
bool is_child, Oid datatype);
static bool is_exprlist_member(Expr *node, List *exprs);
static void generate_base_implied_equalities_const(PlannerInfo *root,
EquivalenceClass *ec);
static void generate_base_implied_equalities_no_const(PlannerInfo *root,
EquivalenceClass *ec);
static void generate_base_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec);
static List *generate_join_implied_equalities_normal(PlannerInfo *root,
EquivalenceClass *ec,
Relids join_relids,
Relids outer_relids,
Relids inner_relids);
static List *generate_join_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec,
Relids nominal_join_relids,
Relids outer_relids,
Relids nominal_inner_relids,
RelOptInfo *inner_rel);
static Oid select_equality_operator(EquivalenceClass *ec,
Oid lefttype, Oid righttype);
static RestrictInfo *create_join_clause(PlannerInfo *root,
EquivalenceClass *ec, Oid opno,
EquivalenceMember *leftem,
EquivalenceMember *rightem,
EquivalenceClass *parent_ec);
static bool reconsider_outer_join_clause(PlannerInfo *root,
RestrictInfo *rinfo,
bool outer_on_left);
static bool reconsider_full_join_clause(PlannerInfo *root,
RestrictInfo *rinfo);
static Bitmapset *get_eclass_indexes_for_relids(PlannerInfo *root,
Relids relids);
static Bitmapset *get_common_eclass_indexes(PlannerInfo *root, Relids relids1,
Relids relids2);
/*
* process_equivalence
* The given clause has a mergejoinable operator and can be applied without
* any delay by an outer join, so its two sides can be considered equal
* anywhere they are both computable; moreover that equality can be
* extended transitively. Record this knowledge in the EquivalenceClass
* data structure, if applicable. Returns true if successful, false if not
* (in which case caller should treat the clause as ordinary, not an
* equivalence).
*
* In some cases, although we cannot convert a clause into EquivalenceClass
* knowledge, we can still modify it to a more useful form than the original.
* Then, *p_restrictinfo will be replaced by a new RestrictInfo, which is what
* the caller should use for further processing.
*
* If below_outer_join is true, then the clause was found below the nullable
* side of an outer join, so its sides might validly be both NULL rather than
* strictly equal. We can still deduce equalities in such cases, but we take
* care to mark an EquivalenceClass if it came from any such clauses. Also,
* we have to check that both sides are either pseudo-constants or strict
* functions of Vars, else they might not both go to NULL above the outer
* join. (This is the main reason why we need a failure return. It's more
* convenient to check this case here than at the call sites...)
*
* We also reject proposed equivalence clauses if they contain leaky functions
* and have security_level above zero. The EC evaluation rules require us to
* apply certain tests at certain joining levels, and we can't tolerate
* delaying any test on security_level grounds. By rejecting candidate clauses
* that might require security delays, we ensure it's safe to apply an EC
* clause as soon as it's supposed to be applied.
*
* On success return, we have also initialized the clause's left_ec/right_ec
* fields to point to the EquivalenceClass representing it. This saves lookup
* effort later.
*
* Note: constructing merged EquivalenceClasses is a standard UNION-FIND
* problem, for which there exist better data structures than simple lists.
* If this code ever proves to be a bottleneck then it could be sped up ---
* but for now, simple is beautiful.
*
* Note: this is only called during planner startup, not during GEQO
* exploration, so we need not worry about whether we're in the right
* memory context.
*/
bool
process_equivalence(PlannerInfo *root,
RestrictInfo **p_restrictinfo,
bool below_outer_join)
{
RestrictInfo *restrictinfo = *p_restrictinfo;
Expr *clause = restrictinfo->clause;
Oid opno,
collation,
item1_type,
item2_type;
Expr *item1;
Expr *item2;
Relids item1_relids,
item2_relids,
item1_nullable_relids,
item2_nullable_relids;
List *opfamilies;
EquivalenceClass *ec1,
*ec2;
EquivalenceMember *em1,
*em2;
ListCell *lc1;
int ec2_idx;
/* Should not already be marked as having generated an eclass */
Assert(restrictinfo->left_ec == NULL);
Assert(restrictinfo->right_ec == NULL);
/* Reject if it is potentially postponable by security considerations */
if (restrictinfo->security_level > 0 && !restrictinfo->leakproof)
return false;
/* Extract info from given clause */
Assert(is_opclause(clause));
opno = ((OpExpr *) clause)->opno;
collation = ((OpExpr *) clause)->inputcollid;
item1 = (Expr *) get_leftop(clause);
item2 = (Expr *) get_rightop(clause);
item1_relids = restrictinfo->left_relids;
item2_relids = restrictinfo->right_relids;
/*
* Ensure both input expressions expose the desired collation (their types
* should be OK already); see comments for canonicalize_ec_expression.
*/
item1 = canonicalize_ec_expression(item1,
exprType((Node *) item1),
collation);
item2 = canonicalize_ec_expression(item2,
exprType((Node *) item2),
collation);
/*
* Clauses of the form X=X cannot be translated into EquivalenceClasses.
* We'd either end up with a single-entry EC, losing the knowledge that
* the clause was present at all, or else make an EC with duplicate
* entries, causing other issues.
*/
if (equal(item1, item2))
{
/*
* If the operator is strict, then the clause can be treated as just
* "X IS NOT NULL". (Since we know we are considering a top-level
* qual, we can ignore the difference between FALSE and NULL results.)
* It's worth making the conversion because we'll typically get a much
* better selectivity estimate than we would for X=X.
*
* If the operator is not strict, we can't be sure what it will do
* with NULLs, so don't attempt to optimize it.
*/
set_opfuncid((OpExpr *) clause);
if (func_strict(((OpExpr *) clause)->opfuncid))
{
NullTest *ntest = makeNode(NullTest);
ntest->arg = item1;
ntest->nulltesttype = IS_NOT_NULL;
ntest->argisrow = false; /* correct even if composite arg */
ntest->location = -1;
*p_restrictinfo =
make_restrictinfo(root,
(Expr *) ntest,
restrictinfo->is_pushed_down,
restrictinfo->outerjoin_delayed,
restrictinfo->pseudoconstant,
restrictinfo->security_level,
NULL,
restrictinfo->outer_relids,
restrictinfo->nullable_relids);
}
return false;
}
/*
* If below outer join, check for strictness, else reject.
*/
if (below_outer_join)
{
if (!bms_is_empty(item1_relids) &&
contain_nonstrict_functions((Node *) item1))
return false; /* LHS is non-strict but not constant */
if (!bms_is_empty(item2_relids) &&
contain_nonstrict_functions((Node *) item2))
return false; /* RHS is non-strict but not constant */
}
/* Calculate nullable-relid sets for each side of the clause */
item1_nullable_relids = bms_intersect(item1_relids,
restrictinfo->nullable_relids);
item2_nullable_relids = bms_intersect(item2_relids,
restrictinfo->nullable_relids);
/*
* We use the declared input types of the operator, not exprType() of the
* inputs, as the nominal datatypes for opfamily lookup. This presumes
* that btree operators are always registered with amoplefttype and
* amoprighttype equal to their declared input types. We will need this
* info anyway to build EquivalenceMember nodes, and by extracting it now
* we can use type comparisons to short-circuit some equal() tests.
*/
op_input_types(opno, &item1_type, &item2_type);
opfamilies = restrictinfo->mergeopfamilies;
/*
* Sweep through the existing EquivalenceClasses looking for matches to
* item1 and item2. These are the possible outcomes:
*
* 1. We find both in the same EC. The equivalence is already known, so
* there's nothing to do.
*
* 2. We find both in different ECs. Merge the two ECs together.
*
* 3. We find just one. Add the other to its EC.
*
* 4. We find neither. Make a new, two-entry EC.
*
* Note: since all ECs are built through this process or the similar
* search in get_eclass_for_sort_expr(), it's impossible that we'd match
* an item in more than one existing nonvolatile EC. So it's okay to stop
* at the first match.
*/
ec1 = ec2 = NULL;
em1 = em2 = NULL;
ec2_idx = -1;
foreach(lc1, root->eq_classes)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
ListCell *lc2;
/* Never match to a volatile EC */
if (cur_ec->ec_has_volatile)
continue;
/*
* The collation has to match; check this first since it's cheaper
* than the opfamily comparison.
*/
if (collation != cur_ec->ec_collation)
continue;
/*
* A "match" requires matching sets of btree opfamilies. Use of
* equal() for this test has implications discussed in the comments
* for get_mergejoin_opfamilies().
*/
if (!equal(opfamilies, cur_ec->ec_opfamilies))
continue;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
Assert(!cur_em->em_is_child); /* no children yet */
/*
* If below an outer join, don't match constants: they're not as
* constant as they look.
*/
if ((below_outer_join || cur_ec->ec_below_outer_join) &&
cur_em->em_is_const)
continue;
if (!ec1 &&
item1_type == cur_em->em_datatype &&
equal(item1, cur_em->em_expr))
{
ec1 = cur_ec;
em1 = cur_em;
if (ec2)
break;
}
if (!ec2 &&
item2_type == cur_em->em_datatype &&
equal(item2, cur_em->em_expr))
{
ec2 = cur_ec;
ec2_idx = foreach_current_index(lc1);
em2 = cur_em;
if (ec1)
break;
}
}
if (ec1 && ec2)
break;
}
/* Sweep finished, what did we find? */
if (ec1 && ec2)
{
/* If case 1, nothing to do, except add to sources */
if (ec1 == ec2)
{
ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
ec1->ec_below_outer_join |= below_outer_join;
ec1->ec_min_security = Min(ec1->ec_min_security,
restrictinfo->security_level);
ec1->ec_max_security = Max(ec1->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
return true;
}
/*
* Case 2: need to merge ec1 and ec2. This should never happen after
* the ECs have reached canonical state; otherwise, pathkeys could be
* rendered non-canonical by the merge, and relation eclass indexes
* would get broken by removal of an eq_classes list entry.
*/
if (root->ec_merging_done)
elog(ERROR, "too late to merge equivalence classes");
/*
* We add ec2's items to ec1, then set ec2's ec_merged link to point
* to ec1 and remove ec2 from the eq_classes list. We cannot simply
* delete ec2 because that could leave dangling pointers in existing
* PathKeys. We leave it behind with a link so that the merged EC can
* be found.
*/
ec1->ec_members = list_concat(ec1->ec_members, ec2->ec_members);
ec1->ec_sources = list_concat(ec1->ec_sources, ec2->ec_sources);
ec1->ec_derives = list_concat(ec1->ec_derives, ec2->ec_derives);
ec1->ec_relids = bms_join(ec1->ec_relids, ec2->ec_relids);
ec1->ec_has_const |= ec2->ec_has_const;
/* can't need to set has_volatile */
ec1->ec_below_outer_join |= ec2->ec_below_outer_join;
ec1->ec_min_security = Min(ec1->ec_min_security,
ec2->ec_min_security);
ec1->ec_max_security = Max(ec1->ec_max_security,
ec2->ec_max_security);
ec2->ec_merged = ec1;
root->eq_classes = list_delete_nth_cell(root->eq_classes, ec2_idx);
/* just to avoid debugging confusion w/ dangling pointers: */
ec2->ec_members = NIL;
ec2->ec_sources = NIL;
ec2->ec_derives = NIL;
ec2->ec_relids = NULL;
ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
ec1->ec_below_outer_join |= below_outer_join;
ec1->ec_min_security = Min(ec1->ec_min_security,
restrictinfo->security_level);
ec1->ec_max_security = Max(ec1->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
else if (ec1)
{
/* Case 3: add item2 to ec1 */
em2 = add_eq_member(ec1, item2, item2_relids, item2_nullable_relids,
false, item2_type);
ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
ec1->ec_below_outer_join |= below_outer_join;
ec1->ec_min_security = Min(ec1->ec_min_security,
restrictinfo->security_level);
ec1->ec_max_security = Max(ec1->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
else if (ec2)
{
/* Case 3: add item1 to ec2 */
em1 = add_eq_member(ec2, item1, item1_relids, item1_nullable_relids,
false, item1_type);
ec2->ec_sources = lappend(ec2->ec_sources, restrictinfo);
ec2->ec_below_outer_join |= below_outer_join;
ec2->ec_min_security = Min(ec2->ec_min_security,
restrictinfo->security_level);
ec2->ec_max_security = Max(ec2->ec_max_security,
restrictinfo->security_level);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec2;
restrictinfo->right_ec = ec2;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
else
{
/* Case 4: make a new, two-entry EC */
EquivalenceClass *ec = makeNode(EquivalenceClass);
ec->ec_opfamilies = opfamilies;
ec->ec_collation = collation;
ec->ec_members = NIL;
ec->ec_sources = list_make1(restrictinfo);
ec->ec_derives = NIL;
ec->ec_relids = NULL;
ec->ec_has_const = false;
ec->ec_has_volatile = false;
ec->ec_below_outer_join = below_outer_join;
ec->ec_broken = false;
ec->ec_sortref = 0;
ec->ec_min_security = restrictinfo->security_level;
ec->ec_max_security = restrictinfo->security_level;
ec->ec_merged = NULL;
em1 = add_eq_member(ec, item1, item1_relids, item1_nullable_relids,
false, item1_type);
em2 = add_eq_member(ec, item2, item2_relids, item2_nullable_relids,
false, item2_type);
root->eq_classes = lappend(root->eq_classes, ec);
/* mark the RI as associated with this eclass */
restrictinfo->left_ec = ec;
restrictinfo->right_ec = ec;
/* mark the RI as usable with this pair of EMs */
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
}
return true;
}
/*
* canonicalize_ec_expression
*
* This function ensures that the expression exposes the expected type and
* collation, so that it will be equal() to other equivalence-class expressions
* that it ought to be equal() to.
*
* The rule for datatypes is that the exposed type should match what it would
* be for an input to an operator of the EC's opfamilies; which is usually
* the declared input type of the operator, but in the case of polymorphic
* operators no relabeling is wanted (compare the behavior of parse_coerce.c).
* Expressions coming in from quals will generally have the right type
* already, but expressions coming from indexkeys may not (because they are
* represented without any explicit relabel in pg_index), and the same problem
* occurs for sort expressions (because the parser is likewise cavalier about
* putting relabels on them). Such cases will be binary-compatible with the
* real operators, so adding a RelabelType is sufficient.
*
* Also, the expression's exposed collation must match the EC's collation.
* This is important because in comparisons like "foo < bar COLLATE baz",
* only one of the expressions has the correct exposed collation as we receive
* it from the parser. Forcing both of them to have it ensures that all
* variant spellings of such a construct behave the same. Again, we can
* stick on a RelabelType to force the right exposed collation. (It might
* work to not label the collation at all in EC members, but this is risky
* since some parts of the system expect exprCollation() to deliver the
* right answer for a sort key.)
*/
Expr *
canonicalize_ec_expression(Expr *expr, Oid req_type, Oid req_collation)
{
Oid expr_type = exprType((Node *) expr);
/*
* For a polymorphic-input-type opclass, just keep the same exposed type.
* RECORD opclasses work like polymorphic-type ones for this purpose.
*/
if (IsPolymorphicType(req_type) || req_type == RECORDOID)
req_type = expr_type;
/*
* No work if the expression exposes the right type/collation already.
*/
if (expr_type != req_type ||
exprCollation((Node *) expr) != req_collation)
{
/*
* If we have to change the type of the expression, set typmod to -1,
* since the new type may not have the same typmod interpretation.
* When we only have to change collation, preserve the exposed typmod.
*/
int32 req_typmod;
if (expr_type != req_type)
req_typmod = -1;
else
req_typmod = exprTypmod((Node *) expr);
/*
* Use applyRelabelType so that we preserve const-flatness. This is
* important since eval_const_expressions has already been applied.
*/
expr = (Expr *) applyRelabelType((Node *) expr,
req_type, req_typmod, req_collation,
COERCE_IMPLICIT_CAST, -1, false);
}
return expr;
}
/*
* add_eq_member - build a new EquivalenceMember and add it to an EC
*/
static EquivalenceMember *
add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
Relids nullable_relids, bool is_child, Oid datatype)
{
EquivalenceMember *em = makeNode(EquivalenceMember);
em->em_expr = expr;
em->em_relids = relids;
em->em_nullable_relids = nullable_relids;
em->em_is_const = false;
em->em_is_child = is_child;
em->em_datatype = datatype;
if (bms_is_empty(relids))
{
/*
* No Vars, assume it's a pseudoconstant. This is correct for entries
* generated from process_equivalence(), because a WHERE clause can't
* contain aggregates or SRFs, and non-volatility was checked before
* process_equivalence() ever got called. But
* get_eclass_for_sort_expr() has to work harder. We put the tests
* there not here to save cycles in the equivalence case.
*/
Assert(!is_child);
em->em_is_const = true;
ec->ec_has_const = true;
/* it can't affect ec_relids */
}
else if (!is_child) /* child members don't add to ec_relids */
{
ec->ec_relids = bms_add_members(ec->ec_relids, relids);
}
ec->ec_members = lappend(ec->ec_members, em);
return em;
}
/*
* get_eclass_for_sort_expr
* Given an expression and opfamily/collation info, find an existing
* equivalence class it is a member of; if none, optionally build a new
* single-member EquivalenceClass for it.
*
* expr is the expression, and nullable_relids is the set of base relids
* that are potentially nullable below it. We actually only care about
* the set of such relids that are used in the expression; but for caller
* convenience, we perform that intersection step here. The caller need
* only be sure that nullable_relids doesn't omit any nullable rels that
* might appear in the expr.
*
* sortref is the SortGroupRef of the originating SortGroupClause, if any,
* or zero if not. (It should never be zero if the expression is volatile!)
*
* If rel is not NULL, it identifies a specific relation we're considering
* a path for, and indicates that child EC members for that relation can be
* considered. Otherwise child members are ignored. (Note: since child EC
* members aren't guaranteed unique, a non-NULL value means that there could
* be more than one EC that matches the expression; if so it's order-dependent
* which one you get. This is annoying but it only happens in corner cases,
* so for now we live with just reporting the first match. See also
* generate_implied_equalities_for_column and match_pathkeys_to_index.)
*
* If create_it is true, we'll build a new EquivalenceClass when there is no
* match. If create_it is false, we just return NULL when no match.
*
* This can be used safely both before and after EquivalenceClass merging;
* since it never causes merging it does not invalidate any existing ECs
* or PathKeys. However, ECs added after path generation has begun are
* of limited usefulness, so usually it's best to create them beforehand.
*
* Note: opfamilies must be chosen consistently with the way
* process_equivalence() would do; that is, generated from a mergejoinable
* equality operator. Else we might fail to detect valid equivalences,
* generating poor (but not incorrect) plans.
*/
EquivalenceClass *
get_eclass_for_sort_expr(PlannerInfo *root,
Expr *expr,
Relids nullable_relids,
List *opfamilies,
Oid opcintype,
Oid collation,
Index sortref,
Relids rel,
bool create_it)
{
Relids expr_relids;
EquivalenceClass *newec;
EquivalenceMember *newem;
ListCell *lc1;
MemoryContext oldcontext;
/*
* Ensure the expression exposes the correct type and collation.
*/
expr = canonicalize_ec_expression(expr, opcintype, collation);
/*
* Scan through the existing EquivalenceClasses for a match
*/
foreach(lc1, root->eq_classes)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
ListCell *lc2;
/*
* Never match to a volatile EC, except when we are looking at another
* reference to the same volatile SortGroupClause.
*/
if (cur_ec->ec_has_volatile &&
(sortref == 0 || sortref != cur_ec->ec_sortref))
continue;
if (collation != cur_ec->ec_collation)
continue;
if (!equal(opfamilies, cur_ec->ec_opfamilies))
continue;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
/*
* Ignore child members unless they match the request.
*/
if (cur_em->em_is_child &&
!bms_equal(cur_em->em_relids, rel))
continue;
/*
* If below an outer join, don't match constants: they're not as
* constant as they look.
*/
if (cur_ec->ec_below_outer_join &&
cur_em->em_is_const)
continue;
if (opcintype == cur_em->em_datatype &&
equal(expr, cur_em->em_expr))
return cur_ec; /* Match! */
}
}
/* No match; does caller want a NULL result? */
if (!create_it)
return NULL;
/*
* OK, build a new single-member EC
*
* Here, we must be sure that we construct the EC in the right context.
*/
oldcontext = MemoryContextSwitchTo(root->planner_cxt);
newec = makeNode(EquivalenceClass);
newec->ec_opfamilies = list_copy(opfamilies);
newec->ec_collation = collation;
newec->ec_members = NIL;
newec->ec_sources = NIL;
newec->ec_derives = NIL;
newec->ec_relids = NULL;
newec->ec_has_const = false;
newec->ec_has_volatile = contain_volatile_functions((Node *) expr);
newec->ec_below_outer_join = false;
newec->ec_broken = false;
newec->ec_sortref = sortref;
newec->ec_min_security = UINT_MAX;
newec->ec_max_security = 0;
newec->ec_merged = NULL;
if (newec->ec_has_volatile && sortref == 0) /* should not happen */
elog(ERROR, "volatile EquivalenceClass has no sortref");
/*
* Get the precise set of nullable relids appearing in the expression.
*/
expr_relids = pull_varnos(root, (Node *) expr);
nullable_relids = bms_intersect(nullable_relids, expr_relids);
newem = add_eq_member(newec, copyObject(expr), expr_relids,
nullable_relids, false, opcintype);
/*
* add_eq_member doesn't check for volatile functions, set-returning
* functions, aggregates, or window functions, but such could appear in
* sort expressions; so we have to check whether its const-marking was
* correct.
*/
if (newec->ec_has_const)
{
if (newec->ec_has_volatile ||
expression_returns_set((Node *) expr) ||
contain_agg_clause((Node *) expr) ||
contain_window_function((Node *) expr))
{
newec->ec_has_const = false;
newem->em_is_const = false;
}
}
root->eq_classes = lappend(root->eq_classes, newec);
/*
* If EC merging is already complete, we have to mop up by adding the new
* EC to the eclass_indexes of the relation(s) mentioned in it.
*/
if (root->ec_merging_done)
{
int ec_index = list_length(root->eq_classes) - 1;
int i = -1;
while ((i = bms_next_member(newec->ec_relids, i)) > 0)
{
RelOptInfo *rel = root->simple_rel_array[i];
Assert(rel->reloptkind == RELOPT_BASEREL ||
rel->reloptkind == RELOPT_DEADREL ||
rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
rel->eclass_indexes = bms_add_member(rel->eclass_indexes,
ec_index);
}
}
MemoryContextSwitchTo(oldcontext);
return newec;
}
/*
* find_ec_member_matching_expr
* Locate an EquivalenceClass member matching the given expr, if any;
* return NULL if no match.
*
* "Matching" is defined as "equal after stripping RelabelTypes".
* This is used for identifying sort expressions, and we need to allow
* binary-compatible relabeling for some cases involving binary-compatible
* sort operators.
*
* Child EC members are ignored unless they belong to given 'relids'.
*/
EquivalenceMember *
find_ec_member_matching_expr(EquivalenceClass *ec,
Expr *expr,
Relids relids)
{
ListCell *lc;
/* We ignore binary-compatible relabeling on both ends */
while (expr && IsA(expr, RelabelType))
expr = ((RelabelType *) expr)->arg;
foreach(lc, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc);
Expr *emexpr;
/*
* We shouldn't be trying to sort by an equivalence class that
* contains a constant, so no need to consider such cases any further.
*/
if (em->em_is_const)
continue;
/*
* Ignore child members unless they belong to the requested rel.
*/
if (em->em_is_child &&
!bms_is_subset(em->em_relids, relids))
continue;
/*
* Match if same expression (after stripping relabel).
*/
emexpr = em->em_expr;
while (emexpr && IsA(emexpr, RelabelType))
emexpr = ((RelabelType *) emexpr)->arg;
if (equal(emexpr, expr))
return em;
}
return NULL;
}
/*
* find_computable_ec_member
* Locate an EquivalenceClass member that can be computed from the
* expressions appearing in "exprs"; return NULL if no match.
*
* "exprs" can be either a list of bare expression trees, or a list of
* TargetEntry nodes. Either way, it should contain Vars and possibly
* Aggrefs and WindowFuncs, which are matched to the corresponding elements
* of the EquivalenceClass's expressions.
*
* Unlike find_ec_member_matching_expr, there's no special provision here
* for binary-compatible relabeling. This is intentional: if we have to
* compute an expression in this way, setrefs.c is going to insist on exact
* matches of Vars to the source tlist.
*
* Child EC members are ignored unless they belong to given 'relids'.
* Also, non-parallel-safe expressions are ignored if 'require_parallel_safe'.
*
* Note: some callers pass root == NULL for notational reasons. This is OK
* when require_parallel_safe is false.
*/
EquivalenceMember *
find_computable_ec_member(PlannerInfo *root,
EquivalenceClass *ec,
List *exprs,
Relids relids,
bool require_parallel_safe)
{
ListCell *lc;
foreach(lc, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc);
List *exprvars;
ListCell *lc2;
/*
* We shouldn't be trying to sort by an equivalence class that
* contains a constant, so no need to consider such cases any further.
*/
if (em->em_is_const)
continue;
/*
* Ignore child members unless they belong to the requested rel.
*/
if (em->em_is_child &&
!bms_is_subset(em->em_relids, relids))
continue;
/*
* Match if all Vars and quasi-Vars are available in "exprs".
*/
exprvars = pull_var_clause((Node *) em->em_expr,
PVC_INCLUDE_AGGREGATES |
PVC_INCLUDE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
foreach(lc2, exprvars)
{
if (!is_exprlist_member(lfirst(lc2), exprs))
break;
}
list_free(exprvars);
if (lc2)
continue; /* we hit a non-available Var */
/*
* If requested, reject expressions that are not parallel-safe. We
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
!is_parallel_safe(root, (Node *) em->em_expr))
continue;
return em; /* found usable expression */
}
return NULL;
}
/*
* is_exprlist_member
* Subroutine for find_computable_ec_member: is "node" in "exprs"?
*
* Per the requirements of that function, "exprs" might or might not have
* TargetEntry superstructure.
*/
static bool
is_exprlist_member(Expr *node, List *exprs)
{
ListCell *lc;
foreach(lc, exprs)
{
Expr *expr = (Expr *) lfirst(lc);
if (expr && IsA(expr, TargetEntry))
expr = ((TargetEntry *) expr)->expr;
if (equal(node, expr))
return true;
}
return false;
}
/*
* Find an equivalence class member expression, all of whose Vars, come from
* the indicated relation.
*/
Expr *
find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
{
ListCell *lc_em;
foreach(lc_em, ec->ec_members)
{
EquivalenceMember *em = lfirst(lc_em);
if (bms_is_subset(em->em_relids, rel->relids) &&
!bms_is_empty(em->em_relids))
{
/*
* If there is more than one equivalence member whose Vars are
* taken entirely from this relation, we'll be content to choose
* any one of those.
*/
return em->em_expr;
}
}
/* We didn't find any suitable equivalence class expression */
return NULL;
}
/*
* relation_can_be_sorted_early
* Can this relation be sorted on this EC before the final output step?
*
* To succeed, we must find an EC member that prepare_sort_from_pathkeys knows
* how to sort on, given the rel's reltarget as input. There are also a few
* additional constraints based on the fact that the desired sort will be done
* "early", within the scan/join part of the plan. Also, non-parallel-safe
* expressions are ignored if 'require_parallel_safe'.
*
* At some point we might want to return the identified EquivalenceMember,
* but for now, callers only want to know if there is one.
*/
bool
relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, bool require_parallel_safe)
{
PathTarget *target = rel->reltarget;
EquivalenceMember *em;
ListCell *lc;
/*
* Reject volatile ECs immediately; such sorts must always be postponed.
*/
if (ec->ec_has_volatile)
return false;
/*
* Try to find an EM directly matching some reltarget member.
*/
foreach(lc, target->exprs)
{
Expr *targetexpr = (Expr *) lfirst(lc);
em = find_ec_member_matching_expr(ec, targetexpr, rel->relids);
if (!em)
continue;
/*
* Reject expressions involving set-returning functions, as those
* can't be computed early either. (Note: this test and the following
* one are effectively checking properties of targetexpr, so there's
* no point in asking whether some other EC member would be better.)
*/
if (IS_SRF_CALL((Node *) em->em_expr))
continue;
/*
* If requested, reject expressions that are not parallel-safe. We
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
!is_parallel_safe(root, (Node *) em->em_expr))
continue;
return true;
}
/*
* Try to find a expression computable from the reltarget.
*/
em = find_computable_ec_member(root, ec, target->exprs, rel->relids,
require_parallel_safe);
if (!em)
return false;
/*
* Reject expressions involving set-returning functions, as those can't be
* computed early either. (There's no point in looking for another EC
* member in this case; since SRFs can't appear in WHERE, they cannot
* belong to multi-member ECs.)
*/
if (IS_SRF_CALL((Node *) em->em_expr))
return false;
return true;
}
/*
* generate_base_implied_equalities
* Generate any restriction clauses that we can deduce from equivalence
* classes.
*
* When an EC contains pseudoconstants, our strategy is to generate
* "member = const1" clauses where const1 is the first constant member, for
* every other member (including other constants). If we are able to do this
* then we don't need any "var = var" comparisons because we've successfully
* constrained all the vars at their points of creation. If we fail to
* generate any of these clauses due to lack of cross-type operators, we fall
* back to the "ec_broken" strategy described below. (XXX if there are
* multiple constants of different types, it's possible that we might succeed
* in forming all the required clauses if we started from a different const
* member; but this seems a sufficiently hokey corner case to not be worth
* spending lots of cycles on.)
*
* For ECs that contain no pseudoconstants, we generate derived clauses
* "member1 = member2" for each pair of members belonging to the same base
* relation (actually, if there are more than two for the same base relation,
* we only need enough clauses to link each to each other). This provides
* the base case for the recursion: each row emitted by a base relation scan
* will constrain all computable members of the EC to be equal. As each
* join path is formed, we'll add additional derived clauses on-the-fly
* to maintain this invariant (see generate_join_implied_equalities).
*
* If the opfamilies used by the EC do not provide complete sets of cross-type
* equality operators, it is possible that we will fail to generate a clause
* that must be generated to maintain the invariant. (An example: given
* "WHERE a.x = b.y AND b.y = a.z", the scheme breaks down if we cannot
* generate "a.x = a.z" as a restriction clause for A.) In this case we mark
* the EC "ec_broken" and fall back to regurgitating its original source
* RestrictInfos at appropriate times. We do not try to retract any derived
* clauses already generated from the broken EC, so the resulting plan could
* be poor due to bad selectivity estimates caused by redundant clauses. But
* the correct solution to that is to fix the opfamilies ...
*
* Equality clauses derived by this function are passed off to
* process_implied_equality (in plan/initsplan.c) to be inserted into the
* restrictinfo datastructures. Note that this must be called after initial
* scanning of the quals and before Path construction begins.
*
* We make no attempt to avoid generating duplicate RestrictInfos here: we
* don't search ec_sources or ec_derives for matches. It doesn't really
* seem worth the trouble to do so.
*/
void
generate_base_implied_equalities(PlannerInfo *root)
{
int ec_index;
ListCell *lc;
/*
* At this point, we're done absorbing knowledge of equivalences in the
* query, so no further EC merging should happen, and ECs remaining in the
* eq_classes list can be considered canonical. (But note that it's still
* possible for new single-member ECs to be added through
* get_eclass_for_sort_expr().)
*/
root->ec_merging_done = true;
ec_index = 0;
foreach(lc, root->eq_classes)
{
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
bool can_generate_joinclause = false;
int i;
Assert(ec->ec_merged == NULL); /* else shouldn't be in list */
Assert(!ec->ec_broken); /* not yet anyway... */
/*
* Generate implied equalities that are restriction clauses.
* Single-member ECs won't generate any deductions, either here or at
* the join level.
*/
if (list_length(ec->ec_members) > 1)
{
if (ec->ec_has_const)
generate_base_implied_equalities_const(root, ec);
else
generate_base_implied_equalities_no_const(root, ec);
/* Recover if we failed to generate required derived clauses */
if (ec->ec_broken)
generate_base_implied_equalities_broken(root, ec);
/* Detect whether this EC might generate join clauses */
can_generate_joinclause =
(bms_membership(ec->ec_relids) == BMS_MULTIPLE);
}
/*
* Mark the base rels cited in each eclass (which should all exist by
* now) with the eq_classes indexes of all eclasses mentioning them.
* This will let us avoid searching in subsequent lookups. While
* we're at it, we can mark base rels that have pending eclass joins;
* this is a cheap version of has_relevant_eclass_joinclause().
*/
i = -1;
while ((i = bms_next_member(ec->ec_relids, i)) > 0)
{
RelOptInfo *rel = root->simple_rel_array[i];
Assert(rel->reloptkind == RELOPT_BASEREL);
rel->eclass_indexes = bms_add_member(rel->eclass_indexes,
ec_index);
if (can_generate_joinclause)
rel->has_eclass_joins = true;
}
ec_index++;
}
}
/*
* generate_base_implied_equalities when EC contains pseudoconstant(s)
*/
static void
generate_base_implied_equalities_const(PlannerInfo *root,
EquivalenceClass *ec)
{
EquivalenceMember *const_em = NULL;
ListCell *lc;
/*
* In the trivial case where we just had one "var = const" clause, push
* the original clause back into the main planner machinery. There is
* nothing to be gained by doing it differently, and we save the effort to
* re-build and re-analyze an equality clause that will be exactly
* equivalent to the old one.
*/
if (list_length(ec->ec_members) == 2 &&
list_length(ec->ec_sources) == 1)
{
RestrictInfo *restrictinfo = (RestrictInfo *) linitial(ec->ec_sources);
if (bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
{
distribute_restrictinfo_to_rels(root, restrictinfo);
return;
}
}
/*
* Find the constant member to use. We prefer an actual constant to
* pseudo-constants (such as Params), because the constraint exclusion
* machinery might be able to exclude relations on the basis of generated
* "var = const" equalities, but "var = param" won't work for that.
*/
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
if (cur_em->em_is_const)
{
const_em = cur_em;
if (IsA(cur_em->em_expr, Const))
break;
}
}
Assert(const_em != NULL);
/* Generate a derived equality against each other member */
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
Oid eq_op;
RestrictInfo *rinfo;
Assert(!cur_em->em_is_child); /* no children yet */
if (cur_em == const_em)
continue;
eq_op = select_equality_operator(ec,
cur_em->em_datatype,
const_em->em_datatype);
if (!OidIsValid(eq_op))
{
/* failed... */
ec->ec_broken = true;
break;
}
rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
cur_em->em_expr, const_em->em_expr,
bms_copy(ec->ec_relids),
bms_union(cur_em->em_nullable_relids,
const_em->em_nullable_relids),
ec->ec_min_security,
ec->ec_below_outer_join,
cur_em->em_is_const);
/*
* If the clause didn't degenerate to a constant, fill in the correct
* markings for a mergejoinable clause, and save it in ec_derives. (We
* will not re-use such clauses directly, but selectivity estimation
* may consult the list later. Note that this use of ec_derives does
* not overlap with its use for join clauses, since we never generate
* join clauses from an ec_has_const eclass.)
*/
if (rinfo && rinfo->mergeopfamilies)
{
/* it's not redundant, so don't set parent_ec */
rinfo->left_ec = rinfo->right_ec = ec;
rinfo->left_em = cur_em;
rinfo->right_em = const_em;
ec->ec_derives = lappend(ec->ec_derives, rinfo);
}
}
}
/*
* generate_base_implied_equalities when EC contains no pseudoconstants
*/
static void
generate_base_implied_equalities_no_const(PlannerInfo *root,
EquivalenceClass *ec)
{
EquivalenceMember **prev_ems;
ListCell *lc;
/*
* We scan the EC members once and track the last-seen member for each
* base relation. When we see another member of the same base relation,
* we generate "prev_em = cur_em". This results in the minimum number of
* derived clauses, but it's possible that it will fail when a different
* ordering would succeed. XXX FIXME: use a UNION-FIND algorithm similar
* to the way we build merged ECs. (Use a list-of-lists for each rel.)
*/
prev_ems = (EquivalenceMember **)
palloc0(root->simple_rel_array_size * sizeof(EquivalenceMember *));
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
int relid;
Assert(!cur_em->em_is_child); /* no children yet */
if (!bms_get_singleton_member(cur_em->em_relids, &relid))
continue;
Assert(relid < root->simple_rel_array_size);
if (prev_ems[relid] != NULL)
{
EquivalenceMember *prev_em = prev_ems[relid];
Oid eq_op;
RestrictInfo *rinfo;
eq_op = select_equality_operator(ec,
prev_em->em_datatype,
cur_em->em_datatype);
if (!OidIsValid(eq_op))
{
/* failed... */
ec->ec_broken = true;
break;
}
rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
prev_em->em_expr, cur_em->em_expr,
bms_copy(ec->ec_relids),
bms_union(prev_em->em_nullable_relids,
cur_em->em_nullable_relids),
ec->ec_min_security,
ec->ec_below_outer_join,
false);
/*
* If the clause didn't degenerate to a constant, fill in the
* correct markings for a mergejoinable clause. We don't put it
* in ec_derives however; we don't currently need to re-find such
* clauses, and we don't want to clutter that list with non-join
* clauses.
*/
if (rinfo && rinfo->mergeopfamilies)
{
/* it's not redundant, so don't set parent_ec */
rinfo->left_ec = rinfo->right_ec = ec;
rinfo->left_em = prev_em;
rinfo->right_em = cur_em;
}
}
prev_ems[relid] = cur_em;
}
pfree(prev_ems);
/*
* We also have to make sure that all the Vars used in the member clauses
* will be available at any join node we might try to reference them at.
* For the moment we force all the Vars to be available at all join nodes
* for this eclass. Perhaps this could be improved by doing some
* pre-analysis of which members we prefer to join, but it's no worse than
* what happened in the pre-8.3 code.
*/
foreach(lc, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
List *vars = pull_var_clause((Node *) cur_em->em_expr,
PVC_RECURSE_AGGREGATES |
PVC_RECURSE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, ec->ec_relids, false);
list_free(vars);
}
}
/*
* generate_base_implied_equalities cleanup after failure
*
* What we must do here is push any zero- or one-relation source RestrictInfos
* of the EC back into the main restrictinfo datastructures. Multi-relation
* clauses will be regurgitated later by generate_join_implied_equalities().
* (We do it this way to maintain continuity with the case that ec_broken
* becomes set only after we've gone up a join level or two.) However, for
* an EC that contains constants, we can adopt a simpler strategy and just
* throw back all the source RestrictInfos immediately; that works because
* we know that such an EC can't become broken later. (This rule justifies
* ignoring ec_has_const ECs in generate_join_implied_equalities, even when
* they are broken.)
*/
static void
generate_base_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec)
{
ListCell *lc;
foreach(lc, ec->ec_sources)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
if (ec->ec_has_const ||
bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
distribute_restrictinfo_to_rels(root, restrictinfo);
}
}
/*
* generate_join_implied_equalities
* Generate any join clauses that we can deduce from equivalence classes.
*
* At a join node, we must enforce restriction clauses sufficient to ensure
* that all equivalence-class members computable at that node are equal.
* Since the set of clauses to enforce can vary depending on which subset
* relations are the inputs, we have to compute this afresh for each join
* relation pair. Hence a fresh List of RestrictInfo nodes is built and
* passed back on each call.
*
* In addition to its use at join nodes, this can be applied to generate
* eclass-based join clauses for use in a parameterized scan of a base rel.
* The reason for the asymmetry of specifying the inner rel as a RelOptInfo
* and the outer rel by Relids is that this usage occurs before we have
* built any join RelOptInfos.
*
* An annoying special case for parameterized scans is that the inner rel can
* be an appendrel child (an "other rel"). In this case we must generate
* appropriate clauses using child EC members. add_child_rel_equivalences
* must already have been done for the child rel.
*
* The results are sufficient for use in merge, hash, and plain nestloop join
* methods. We do not worry here about selecting clauses that are optimal
* for use in a parameterized indexscan. indxpath.c makes its own selections
* of clauses to use, and if the ones we pick here are redundant with those,
* the extras will be eliminated at createplan time, using the parent_ec
* markers that we provide (see is_redundant_derived_clause()).
*
* Because the same join clauses are likely to be needed multiple times as
* we consider different join paths, we avoid generating multiple copies:
* whenever we select a particular pair of EquivalenceMembers to join,
* we check to see if the pair matches any original clause (in ec_sources)
* or previously-built clause (in ec_derives). This saves memory and allows
* re-use of information cached in RestrictInfos.
*
* join_relids should always equal bms_union(outer_relids, inner_rel->relids).
* We could simplify this function's API by computing it internally, but in
* most current uses, the caller has the value at hand anyway.
*/
List *
generate_join_implied_equalities(PlannerInfo *root,
Relids join_relids,
Relids outer_relids,
RelOptInfo *inner_rel)
{
List *result = NIL;
Relids inner_relids = inner_rel->relids;
Relids nominal_inner_relids;
Relids nominal_join_relids;
Bitmapset *matching_ecs;
int i;
/* If inner rel is a child, extra setup work is needed */
if (IS_OTHER_REL(inner_rel))
{
Assert(!bms_is_empty(inner_rel->top_parent_relids));
/* Fetch relid set for the topmost parent rel */
nominal_inner_relids = inner_rel->top_parent_relids;
/* ECs will be marked with the parent's relid, not the child's */
nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
}
else
{
nominal_inner_relids = inner_relids;
nominal_join_relids = join_relids;
}
/*
* Get all eclasses that mention both inner and outer sides of the join
*/
matching_ecs = get_common_eclass_indexes(root, nominal_inner_relids,
outer_relids);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
List *sublist = NIL;
/* ECs containing consts do not need any further enforcement */
if (ec->ec_has_const)
continue;
/* Single-member ECs won't generate any deductions */
if (list_length(ec->ec_members) <= 1)
continue;
/* Sanity check that this eclass overlaps the join */
Assert(bms_overlap(ec->ec_relids, nominal_join_relids));
if (!ec->ec_broken)
sublist = generate_join_implied_equalities_normal(root,
ec,
join_relids,
outer_relids,
inner_relids);
/* Recover if we failed to generate required derived clauses */
if (ec->ec_broken)
sublist = generate_join_implied_equalities_broken(root,
ec,
nominal_join_relids,
outer_relids,
nominal_inner_relids,
inner_rel);
result = list_concat(result, sublist);
}
return result;
}
/*
* generate_join_implied_equalities_for_ecs
* As above, but consider only the listed ECs.
*/
List *
generate_join_implied_equalities_for_ecs(PlannerInfo *root,
List *eclasses,
Relids join_relids,
Relids outer_relids,
RelOptInfo *inner_rel)
{
List *result = NIL;
Relids inner_relids = inner_rel->relids;
Relids nominal_inner_relids;
Relids nominal_join_relids;
ListCell *lc;
/* If inner rel is a child, extra setup work is needed */
if (IS_OTHER_REL(inner_rel))
{
Assert(!bms_is_empty(inner_rel->top_parent_relids));
/* Fetch relid set for the topmost parent rel */
nominal_inner_relids = inner_rel->top_parent_relids;
/* ECs will be marked with the parent's relid, not the child's */
nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
}
else
{
nominal_inner_relids = inner_relids;
nominal_join_relids = join_relids;
}
foreach(lc, eclasses)
{
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
List *sublist = NIL;
/* ECs containing consts do not need any further enforcement */
if (ec->ec_has_const)
continue;
/* Single-member ECs won't generate any deductions */
if (list_length(ec->ec_members) <= 1)
continue;
/* We can quickly ignore any that don't overlap the join, too */
if (!bms_overlap(ec->ec_relids, nominal_join_relids))
continue;
if (!ec->ec_broken)
sublist = generate_join_implied_equalities_normal(root,
ec,
join_relids,
outer_relids,
inner_relids);
/* Recover if we failed to generate required derived clauses */
if (ec->ec_broken)
sublist = generate_join_implied_equalities_broken(root,
ec,
nominal_join_relids,
outer_relids,
nominal_inner_relids,
inner_rel);
result = list_concat(result, sublist);
}
return result;
}
/*
* generate_join_implied_equalities for a still-valid EC
*/
static List *
generate_join_implied_equalities_normal(PlannerInfo *root,
EquivalenceClass *ec,
Relids join_relids,
Relids outer_relids,
Relids inner_relids)
{
List *result = NIL;
List *new_members = NIL;
List *outer_members = NIL;
List *inner_members = NIL;
ListCell *lc1;
/*
* First, scan the EC to identify member values that are computable at the
* outer rel, at the inner rel, or at this relation but not in either
* input rel. The outer-rel members should already be enforced equal,
* likewise for the inner-rel members. We'll need to create clauses to
* enforce that any newly computable members are all equal to each other
* as well as to at least one input member, plus enforce at least one
* outer-rel member equal to at least one inner-rel member.
*/
foreach(lc1, ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
/*
* We don't need to check explicitly for child EC members. This test
* against join_relids will cause them to be ignored except when
* considering a child inner rel, which is what we want.
*/
if (!bms_is_subset(cur_em->em_relids, join_relids))
continue; /* not computable yet, or wrong child */
if (bms_is_subset(cur_em->em_relids, outer_relids))
outer_members = lappend(outer_members, cur_em);
else if (bms_is_subset(cur_em->em_relids, inner_relids))
inner_members = lappend(inner_members, cur_em);
else
new_members = lappend(new_members, cur_em);
}
/*
* First, select the joinclause if needed. We can equate any one outer
* member to any one inner member, but we have to find a datatype
* combination for which an opfamily member operator exists. If we have
* choices, we prefer simple Var members (possibly with RelabelType) since
* these are (a) cheapest to compute at runtime and (b) most likely to
* have useful statistics. Also, prefer operators that are also
* hashjoinable.
*/
if (outer_members && inner_members)
{
EquivalenceMember *best_outer_em = NULL;
EquivalenceMember *best_inner_em = NULL;
Oid best_eq_op = InvalidOid;
int best_score = -1;
RestrictInfo *rinfo;
foreach(lc1, outer_members)
{
EquivalenceMember *outer_em = (EquivalenceMember *) lfirst(lc1);
ListCell *lc2;
foreach(lc2, inner_members)
{
EquivalenceMember *inner_em = (EquivalenceMember *) lfirst(lc2);
Oid eq_op;
int score;
eq_op = select_equality_operator(ec,
outer_em->em_datatype,
inner_em->em_datatype);
if (!OidIsValid(eq_op))
continue;
score = 0;
if (IsA(outer_em->em_expr, Var) ||
(IsA(outer_em->em_expr, RelabelType) &&
IsA(((RelabelType *) outer_em->em_expr)->arg, Var)))
score++;
if (IsA(inner_em->em_expr, Var) ||
(IsA(inner_em->em_expr, RelabelType) &&
IsA(((RelabelType *) inner_em->em_expr)->arg, Var)))
score++;
if (op_hashjoinable(eq_op,
exprType((Node *) outer_em->em_expr)))
score++;
if (score > best_score)
{
best_outer_em = outer_em;
best_inner_em = inner_em;
best_eq_op = eq_op;
best_score = score;
if (best_score == 3)
break; /* no need to look further */
}
}
if (best_score == 3)
break; /* no need to look further */
}
if (best_score < 0)
{
/* failed... */
ec->ec_broken = true;
return NIL;
}
/*
* Create clause, setting parent_ec to mark it as redundant with other
* joinclauses
*/
rinfo = create_join_clause(root, ec, best_eq_op,
best_outer_em, best_inner_em,
ec);
result = lappend(result, rinfo);
}
/*
* Now deal with building restrictions for any expressions that involve
* Vars from both sides of the join. We have to equate all of these to
* each other as well as to at least one old member (if any).
*
* XXX as in generate_base_implied_equalities_no_const, we could be a lot
* smarter here to avoid unnecessary failures in cross-type situations.
* For now, use the same left-to-right method used there.
*/
if (new_members)
{
List *old_members = list_concat(outer_members, inner_members);
EquivalenceMember *prev_em = NULL;
RestrictInfo *rinfo;
/* For now, arbitrarily take the first old_member as the one to use */
if (old_members)
new_members = lappend(new_members, linitial(old_members));
foreach(lc1, new_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
if (prev_em != NULL)
{
Oid eq_op;
eq_op = select_equality_operator(ec,
prev_em->em_datatype,
cur_em->em_datatype);
if (!OidIsValid(eq_op))
{
/* failed... */
ec->ec_broken = true;
return NIL;
}
/* do NOT set parent_ec, this qual is not redundant! */
rinfo = create_join_clause(root, ec, eq_op,
prev_em, cur_em,
NULL);
result = lappend(result, rinfo);
}
prev_em = cur_em;
}
}
return result;
}
/*
* generate_join_implied_equalities cleanup after failure
*
* Return any original RestrictInfos that are enforceable at this join.
*
* In the case of a child inner relation, we have to translate the
* original RestrictInfos from parent to child Vars.
*/
static List *
generate_join_implied_equalities_broken(PlannerInfo *root,
EquivalenceClass *ec,
Relids nominal_join_relids,
Relids outer_relids,
Relids nominal_inner_relids,
RelOptInfo *inner_rel)
{
List *result = NIL;
ListCell *lc;
foreach(lc, ec->ec_sources)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
Relids clause_relids = restrictinfo->required_relids;
if (bms_is_subset(clause_relids, nominal_join_relids) &&
!bms_is_subset(clause_relids, outer_relids) &&
!bms_is_subset(clause_relids, nominal_inner_relids))
result = lappend(result, restrictinfo);
}
/*
* If we have to translate, just brute-force apply adjust_appendrel_attrs
* to all the RestrictInfos at once. This will result in returning
* RestrictInfos that are not listed in ec_derives, but there shouldn't be
* any duplication, and it's a sufficiently narrow corner case that we
* shouldn't sweat too much over it anyway.
*
* Since inner_rel might be an indirect descendant of the baserel
* mentioned in the ec_sources clauses, we have to be prepared to apply
* multiple levels of Var translation.
*/
if (IS_OTHER_REL(inner_rel) && result != NIL)
result = (List *) adjust_appendrel_attrs_multilevel(root,
(Node *) result,
inner_rel->relids,
inner_rel->top_parent_relids);
return result;
}
/*
* select_equality_operator
* Select a suitable equality operator for comparing two EC members
*
* Returns InvalidOid if no operator can be found for this datatype combination
*/
static Oid
select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype)
{
ListCell *lc;
foreach(lc, ec->ec_opfamilies)
{
Oid opfamily = lfirst_oid(lc);
Oid opno;
opno = get_opfamily_member(opfamily, lefttype, righttype,
BTEqualStrategyNumber);
if (!OidIsValid(opno))
continue;
/* If no barrier quals in query, don't worry about leaky operators */
if (ec->ec_max_security == 0)
return opno;
/* Otherwise, insist that selected operators be leakproof */
if (get_func_leakproof(get_opcode(opno)))
return opno;
}
return InvalidOid;
}
/*
* create_join_clause
* Find or make a RestrictInfo comparing the two given EC members
* with the given operator.
*
* parent_ec is either equal to ec (if the clause is a potentially-redundant
* join clause) or NULL (if not). We have to treat this as part of the
* match requirements --- it's possible that a clause comparing the same two
* EMs is a join clause in one join path and a restriction clause in another.
*/
static RestrictInfo *
create_join_clause(PlannerInfo *root,
EquivalenceClass *ec, Oid opno,
EquivalenceMember *leftem,
EquivalenceMember *rightem,
EquivalenceClass *parent_ec)
{
RestrictInfo *rinfo;
ListCell *lc;
MemoryContext oldcontext;
/*
* Search to see if we already built a RestrictInfo for this pair of
* EquivalenceMembers. We can use either original source clauses or
* previously-derived clauses. The check on opno is probably redundant,
* but be safe ...
*/
foreach(lc, ec->ec_sources)
{
rinfo = (RestrictInfo *) lfirst(lc);
if (rinfo->left_em == leftem &&
rinfo->right_em == rightem &&
rinfo->parent_ec == parent_ec &&
opno == ((OpExpr *) rinfo->clause)->opno)
return rinfo;
}
foreach(lc, ec->ec_derives)
{
rinfo = (RestrictInfo *) lfirst(lc);
if (rinfo->left_em == leftem &&
rinfo->right_em == rightem &&
rinfo->parent_ec == parent_ec &&
opno == ((OpExpr *) rinfo->clause)->opno)
return rinfo;
}
/*
* Not there, so build it, in planner context so we can re-use it. (Not
* important in normal planning, but definitely so in GEQO.)
*/
oldcontext = MemoryContextSwitchTo(root->planner_cxt);
rinfo = build_implied_join_equality(root,
opno,
ec->ec_collation,
leftem->em_expr,
rightem->em_expr,
bms_union(leftem->em_relids,
rightem->em_relids),
bms_union(leftem->em_nullable_relids,
rightem->em_nullable_relids),
ec->ec_min_security);
/* Mark the clause as redundant, or not */
rinfo->parent_ec = parent_ec;
/*
* We know the correct values for left_ec/right_ec, ie this particular EC,
* so we can just set them directly instead of forcing another lookup.
*/
rinfo->left_ec = ec;
rinfo->right_ec = ec;
/* Mark it as usable with these EMs */
rinfo->left_em = leftem;
rinfo->right_em = rightem;
/* and save it for possible re-use */
ec->ec_derives = lappend(ec->ec_derives, rinfo);
MemoryContextSwitchTo(oldcontext);
return rinfo;
}
/*
* reconsider_outer_join_clauses
* Re-examine any outer-join clauses that were set aside by
* distribute_qual_to_rels(), and see if we can derive any
* EquivalenceClasses from them. Then, if they were not made
* redundant, push them out into the regular join-clause lists.
*
* When we have mergejoinable clauses A = B that are outer-join clauses,
* we can't blindly combine them with other clauses A = C to deduce B = C,
* since in fact the "equality" A = B won't necessarily hold above the
* outer join (one of the variables might be NULL instead). Nonetheless
* there are cases where we can add qual clauses using transitivity.
*
* One case that we look for here is an outer-join clause OUTERVAR = INNERVAR
* for which there is also an equivalence clause OUTERVAR = CONSTANT.
* It is safe and useful to push a clause INNERVAR = CONSTANT into the
* evaluation of the inner (nullable) relation, because any inner rows not
* meeting this condition will not contribute to the outer-join result anyway.
* (Any outer rows they could join to will be eliminated by the pushed-down
* equivalence clause.)
*
* Note that the above rule does not work for full outer joins; nor is it
* very interesting to consider cases where the generated equivalence clause
* would involve relations outside the outer join, since such clauses couldn't
* be pushed into the inner side's scan anyway. So the restriction to
* outervar = pseudoconstant is not really giving up anything.
*
* For full-join cases, we can only do something useful if it's a FULL JOIN
* USING and a merged column has an equivalence MERGEDVAR = CONSTANT.
* By the time it gets here, the merged column will look like
* COALESCE(LEFTVAR, RIGHTVAR)
* and we will have a full-join clause LEFTVAR = RIGHTVAR that we can match
* the COALESCE expression to. In this situation we can push LEFTVAR = CONSTANT
* and RIGHTVAR = CONSTANT into the input relations, since any rows not
* meeting these conditions cannot contribute to the join result.
*
* Again, there isn't any traction to be gained by trying to deal with
* clauses comparing a mergedvar to a non-pseudoconstant. So we can make
* use of the EquivalenceClasses to search for matching variables that were
* equivalenced to constants. The interesting outer-join clauses were
* accumulated for us by distribute_qual_to_rels.
*
* When we find one of these cases, we implement the changes we want by
* generating a new equivalence clause INNERVAR = CONSTANT (or LEFTVAR, etc)
* and pushing it into the EquivalenceClass structures. This is because we
* may already know that INNERVAR is equivalenced to some other var(s), and
* we'd like the constant to propagate to them too. Note that it would be
* unsafe to merge any existing EC for INNERVAR with the OUTERVAR's EC ---
* that could result in propagating constant restrictions from
* INNERVAR to OUTERVAR, which would be very wrong.
*
* It's possible that the INNERVAR is also an OUTERVAR for some other
* outer-join clause, in which case the process can be repeated. So we repeat
* looping over the lists of clauses until no further deductions can be made.
* Whenever we do make a deduction, we remove the generating clause from the
* lists, since we don't want to make the same deduction twice.
*
* If we don't find any match for a set-aside outer join clause, we must
* throw it back into the regular joinclause processing by passing it to
* distribute_restrictinfo_to_rels(). If we do generate a derived clause,
* however, the outer-join clause is redundant. We still throw it back,
* because otherwise the join will be seen as a clauseless join and avoided
* during join order searching; but we mark it as redundant to keep from
* messing up the joinrel's size estimate. (This behavior means that the
* API for this routine is uselessly complex: we could have just put all
* the clauses into the regular processing initially. We keep it because
* someday we might want to do something else, such as inserting "dummy"
* joinclauses instead of real ones.)
*
* Outer join clauses that are marked outerjoin_delayed are special: this
* condition means that one or both VARs might go to null due to a lower
* outer join. We can still push a constant through the clause, but only
* if its operator is strict; and we *have to* throw the clause back into
* regular joinclause processing. By keeping the strict join clause,
* we ensure that any null-extended rows that are mistakenly generated due
* to suppressing rows not matching the constant will be rejected at the
* upper outer join. (This doesn't work for full-join clauses.)
*/
void
reconsider_outer_join_clauses(PlannerInfo *root)
{
bool found;
ListCell *cell;
/* Outer loop repeats until we find no more deductions */
do
{
found = false;
/* Process the LEFT JOIN clauses */
foreach(cell, root->left_join_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
if (reconsider_outer_join_clause(root, rinfo, true))
{
found = true;
/* remove it from the list */
root->left_join_clauses =
foreach_delete_current(root->left_join_clauses, cell);
/* we throw it back anyway (see notes above) */
/* but the thrown-back clause has no extra selectivity */
rinfo->norm_selec = 2.0;
rinfo->outer_selec = 1.0;
distribute_restrictinfo_to_rels(root, rinfo);
}
}
/* Process the RIGHT JOIN clauses */
foreach(cell, root->right_join_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
if (reconsider_outer_join_clause(root, rinfo, false))
{
found = true;
/* remove it from the list */
root->right_join_clauses =
foreach_delete_current(root->right_join_clauses, cell);
/* we throw it back anyway (see notes above) */
/* but the thrown-back clause has no extra selectivity */
rinfo->norm_selec = 2.0;
rinfo->outer_selec = 1.0;
distribute_restrictinfo_to_rels(root, rinfo);
}
}
/* Process the FULL JOIN clauses */
foreach(cell, root->full_join_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
if (reconsider_full_join_clause(root, rinfo))
{
found = true;
/* remove it from the list */
root->full_join_clauses =
foreach_delete_current(root->full_join_clauses, cell);
/* we throw it back anyway (see notes above) */
/* but the thrown-back clause has no extra selectivity */
rinfo->norm_selec = 2.0;
rinfo->outer_selec = 1.0;
distribute_restrictinfo_to_rels(root, rinfo);
}
}
} while (found);
/* Now, any remaining clauses have to be thrown back */
foreach(cell, root->left_join_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
distribute_restrictinfo_to_rels(root, rinfo);
}
foreach(cell, root->right_join_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
distribute_restrictinfo_to_rels(root, rinfo);
}
foreach(cell, root->full_join_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
distribute_restrictinfo_to_rels(root, rinfo);
}
}
/*
* reconsider_outer_join_clauses for a single LEFT/RIGHT JOIN clause
*
* Returns true if we were able to propagate a constant through the clause.
*/
static bool
reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo,
bool outer_on_left)
{
Expr *outervar,
*innervar;
Oid opno,
collation,
left_type,
right_type,
inner_datatype;
Relids inner_relids,
inner_nullable_relids;
ListCell *lc1;
Assert(is_opclause(rinfo->clause));
opno = ((OpExpr *) rinfo->clause)->opno;
collation = ((OpExpr *) rinfo->clause)->inputcollid;
/* If clause is outerjoin_delayed, operator must be strict */
if (rinfo->outerjoin_delayed && !op_strict(opno))
return false;
/* Extract needed info from the clause */
op_input_types(opno, &left_type, &right_type);
if (outer_on_left)
{
outervar = (Expr *) get_leftop(rinfo->clause);
innervar = (Expr *) get_rightop(rinfo->clause);
inner_datatype = right_type;
inner_relids = rinfo->right_relids;
}
else
{
outervar = (Expr *) get_rightop(rinfo->clause);
innervar = (Expr *) get_leftop(rinfo->clause);
inner_datatype = left_type;
inner_relids = rinfo->left_relids;
}
inner_nullable_relids = bms_intersect(inner_relids,
rinfo->nullable_relids);
/* Scan EquivalenceClasses for a match to outervar */
foreach(lc1, root->eq_classes)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
bool match;
ListCell *lc2;
/* Ignore EC unless it contains pseudoconstants */
if (!cur_ec->ec_has_const)
continue;
/* Never match to a volatile EC */
if (cur_ec->ec_has_volatile)
continue;
/* It has to match the outer-join clause as to semantics, too */
if (collation != cur_ec->ec_collation)
continue;
if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
continue;
/* Does it contain a match to outervar? */
match = false;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
Assert(!cur_em->em_is_child); /* no children yet */
if (equal(outervar, cur_em->em_expr))
{
match = true;
break;
}
}
if (!match)
continue; /* no match, so ignore this EC */
/*
* Yes it does! Try to generate a clause INNERVAR = CONSTANT for each
* CONSTANT in the EC. Note that we must succeed with at least one
* constant before we can decide to throw away the outer-join clause.
*/
match = false;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
Oid eq_op;
RestrictInfo *newrinfo;
if (!cur_em->em_is_const)
continue; /* ignore non-const members */
eq_op = select_equality_operator(cur_ec,
inner_datatype,
cur_em->em_datatype);
if (!OidIsValid(eq_op))
continue; /* can't generate equality */
newrinfo = build_implied_join_equality(root,
eq_op,
cur_ec->ec_collation,
innervar,
cur_em->em_expr,
bms_copy(inner_relids),
bms_copy(inner_nullable_relids),
cur_ec->ec_min_security);
if (process_equivalence(root, &newrinfo, true))
match = true;
}
/*
* If we were able to equate INNERVAR to any constant, report success.
* Otherwise, fall out of the search loop, since we know the OUTERVAR
* appears in at most one EC.
*/
if (match)
return true;
else
break;
}
return false; /* failed to make any deduction */
}
/*
* reconsider_outer_join_clauses for a single FULL JOIN clause
*
* Returns true if we were able to propagate a constant through the clause.
*/
static bool
reconsider_full_join_clause(PlannerInfo *root, RestrictInfo *rinfo)
{
Expr *leftvar;
Expr *rightvar;
Oid opno,
collation,
left_type,
right_type;
Relids left_relids,
right_relids,
left_nullable_relids,
right_nullable_relids;
ListCell *lc1;
/* Can't use an outerjoin_delayed clause here */
if (rinfo->outerjoin_delayed)
return false;
/* Extract needed info from the clause */
Assert(is_opclause(rinfo->clause));
opno = ((OpExpr *) rinfo->clause)->opno;
collation = ((OpExpr *) rinfo->clause)->inputcollid;
op_input_types(opno, &left_type, &right_type);
leftvar = (Expr *) get_leftop(rinfo->clause);
rightvar = (Expr *) get_rightop(rinfo->clause);
left_relids = rinfo->left_relids;
right_relids = rinfo->right_relids;
left_nullable_relids = bms_intersect(left_relids,
rinfo->nullable_relids);
right_nullable_relids = bms_intersect(right_relids,
rinfo->nullable_relids);
foreach(lc1, root->eq_classes)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
EquivalenceMember *coal_em = NULL;
bool match;
bool matchleft;
bool matchright;
ListCell *lc2;
int coal_idx = -1;
/* Ignore EC unless it contains pseudoconstants */
if (!cur_ec->ec_has_const)
continue;
/* Never match to a volatile EC */
if (cur_ec->ec_has_volatile)
continue;
/* It has to match the outer-join clause as to semantics, too */
if (collation != cur_ec->ec_collation)
continue;
if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
continue;
/*
* Does it contain a COALESCE(leftvar, rightvar) construct?
*
* We can assume the COALESCE() inputs are in the same order as the
* join clause, since both were automatically generated in the cases
* we care about.
*
* XXX currently this may fail to match in cross-type cases because
* the COALESCE will contain typecast operations while the join clause
* may not (if there is a cross-type mergejoin operator available for
* the two column types). Is it OK to strip implicit coercions from
* the COALESCE arguments?
*/
match = false;
foreach(lc2, cur_ec->ec_members)
{
coal_em = (EquivalenceMember *) lfirst(lc2);
Assert(!coal_em->em_is_child); /* no children yet */
if (IsA(coal_em->em_expr, CoalesceExpr))
{
CoalesceExpr *cexpr = (CoalesceExpr *) coal_em->em_expr;
Node *cfirst;
Node *csecond;
if (list_length(cexpr->args) != 2)
continue;
cfirst = (Node *) linitial(cexpr->args);
csecond = (Node *) lsecond(cexpr->args);
if (equal(leftvar, cfirst) && equal(rightvar, csecond))
{
coal_idx = foreach_current_index(lc2);
match = true;
break;
}
}
}
if (!match)
continue; /* no match, so ignore this EC */
/*
* Yes it does! Try to generate clauses LEFTVAR = CONSTANT and
* RIGHTVAR = CONSTANT for each CONSTANT in the EC. Note that we must
* succeed with at least one constant for each var before we can
* decide to throw away the outer-join clause.
*/
matchleft = matchright = false;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
Oid eq_op;
RestrictInfo *newrinfo;
if (!cur_em->em_is_const)
continue; /* ignore non-const members */
eq_op = select_equality_operator(cur_ec,
left_type,
cur_em->em_datatype);
if (OidIsValid(eq_op))
{
newrinfo = build_implied_join_equality(root,
eq_op,
cur_ec->ec_collation,
leftvar,
cur_em->em_expr,
bms_copy(left_relids),
bms_copy(left_nullable_relids),
cur_ec->ec_min_security);
if (process_equivalence(root, &newrinfo, true))
matchleft = true;
}
eq_op = select_equality_operator(cur_ec,
right_type,
cur_em->em_datatype);
if (OidIsValid(eq_op))
{
newrinfo = build_implied_join_equality(root,
eq_op,
cur_ec->ec_collation,
rightvar,
cur_em->em_expr,
bms_copy(right_relids),
bms_copy(right_nullable_relids),
cur_ec->ec_min_security);
if (process_equivalence(root, &newrinfo, true))
matchright = true;
}
}
/*
* If we were able to equate both vars to constants, we're done, and
* we can throw away the full-join clause as redundant. Moreover, we
* can remove the COALESCE entry from the EC, since the added
* restrictions ensure it will always have the expected value. (We
* don't bother trying to update ec_relids or ec_sources.)
*/
if (matchleft && matchright)
{
cur_ec->ec_members = list_delete_nth_cell(cur_ec->ec_members, coal_idx);
return true;
}
/*
* Otherwise, fall out of the search loop, since we know the COALESCE
* appears in at most one EC (XXX might stop being true if we allow
* stripping of coercions above?)
*/
break;
}
return false; /* failed to make any deduction */
}
/*
* exprs_known_equal
* Detect whether two expressions are known equal due to equivalence
* relationships.
*
* Actually, this only shows that the expressions are equal according
* to some opfamily's notion of equality --- but we only use it for
* selectivity estimation, so a fuzzy idea of equality is OK.
*
* Note: does not bother to check for "equal(item1, item2)"; caller must
* check that case if it's possible to pass identical items.
*/
bool
exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2)
{
ListCell *lc1;
foreach(lc1, root->eq_classes)
{
EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
bool item1member = false;
bool item2member = false;
ListCell *lc2;
/* Never match to a volatile EC */
if (ec->ec_has_volatile)
continue;
foreach(lc2, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
if (em->em_is_child)
continue; /* ignore children here */
if (equal(item1, em->em_expr))
item1member = true;
else if (equal(item2, em->em_expr))
item2member = true;
/* Exit as soon as equality is proven */
if (item1member && item2member)
return true;
}
}
return false;
}
/*
* match_eclasses_to_foreign_key_col
* See whether a foreign key column match is proven by any eclass.
*
* If the referenced and referencing Vars of the fkey's colno'th column are
* known equal due to any eclass, return that eclass; otherwise return NULL.
* (In principle there might be more than one matching eclass if multiple
* collations are involved, but since collation doesn't matter for equality,
* we ignore that fine point here.) This is much like exprs_known_equal,
* except that we insist on the comparison operator matching the eclass, so
* that the result is definite not approximate.
*
* On success, we also set fkinfo->eclass[colno] to the matching eclass,
* and set fkinfo->fk_eclass_member[colno] to the eclass member for the
* referencing Var.
*/
EquivalenceClass *
match_eclasses_to_foreign_key_col(PlannerInfo *root,
ForeignKeyOptInfo *fkinfo,
int colno)
{
Index var1varno = fkinfo->con_relid;
AttrNumber var1attno = fkinfo->conkey[colno];
Index var2varno = fkinfo->ref_relid;
AttrNumber var2attno = fkinfo->confkey[colno];
Oid eqop = fkinfo->conpfeqop[colno];
RelOptInfo *rel1 = root->simple_rel_array[var1varno];
RelOptInfo *rel2 = root->simple_rel_array[var2varno];
List *opfamilies = NIL; /* compute only if needed */
Bitmapset *matching_ecs;
int i;
/* Consider only eclasses mentioning both relations */
Assert(root->ec_merging_done);
Assert(IS_SIMPLE_REL(rel1));
Assert(IS_SIMPLE_REL(rel2));
matching_ecs = bms_intersect(rel1->eclass_indexes,
rel2->eclass_indexes);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
i);
EquivalenceMember *item1_em = NULL;
EquivalenceMember *item2_em = NULL;
ListCell *lc2;
/* Never match to a volatile EC */
if (ec->ec_has_volatile)
continue;
/* Note: it seems okay to match to "broken" eclasses here */
foreach(lc2, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
Var *var;
if (em->em_is_child)
continue; /* ignore children here */
/* EM must be a Var, possibly with RelabelType */
var = (Var *) em->em_expr;
while (var && IsA(var, RelabelType))
var = (Var *) ((RelabelType *) var)->arg;
if (!(var && IsA(var, Var)))
continue;
/* Match? */
if (var->varno == var1varno && var->varattno == var1attno)
item1_em = em;
else if (var->varno == var2varno && var->varattno == var2attno)
item2_em = em;
/* Have we found both PK and FK column in this EC? */
if (item1_em && item2_em)
{
/*
* Succeed if eqop matches EC's opfamilies. We could test
* this before scanning the members, but it's probably cheaper
* to test for member matches first.
*/
if (opfamilies == NIL) /* compute if we didn't already */
opfamilies = get_mergejoin_opfamilies(eqop);
if (equal(opfamilies, ec->ec_opfamilies))
{
fkinfo->eclass[colno] = ec;
fkinfo->fk_eclass_member[colno] = item2_em;
return ec;
}
/* Otherwise, done with this EC, move on to the next */
break;
}
}
}
return NULL;
}
/*
* find_derived_clause_for_ec_member
* Search for a previously-derived clause mentioning the given EM.
*
* The eclass should be an ec_has_const EC, of which the EM is a non-const
* member. This should ensure there is just one derived clause mentioning
* the EM (and equating it to a constant).
* Returns NULL if no such clause can be found.
*/
RestrictInfo *
find_derived_clause_for_ec_member(EquivalenceClass *ec,
EquivalenceMember *em)
{
ListCell *lc;
Assert(ec->ec_has_const);
Assert(!em->em_is_const);
foreach(lc, ec->ec_derives)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
/*
* generate_base_implied_equalities_const will have put non-const
* members on the left side of derived clauses.
*/
if (rinfo->left_em == em)
return rinfo;
}
return NULL;
}
/*
* add_child_rel_equivalences
* Search for EC members that reference the root parent of child_rel, and
* add transformed members referencing the child_rel.
*
* Note that this function won't be called at all unless we have at least some
* reason to believe that the EC members it generates will be useful.
*
* parent_rel and child_rel could be derived from appinfo, but since the
* caller has already computed them, we might as well just pass them in.
*
* The passed-in AppendRelInfo is not used when the parent_rel is not a
* top-level baserel, since it shows the mapping from the parent_rel but
* we need to translate EC expressions that refer to the top-level parent.
* Using it is faster than using adjust_appendrel_attrs_multilevel(), though,
* so we prefer it when we can.
*/
void
add_child_rel_equivalences(PlannerInfo *root,
AppendRelInfo *appinfo,
RelOptInfo *parent_rel,
RelOptInfo *child_rel)
{
Relids top_parent_relids = child_rel->top_parent_relids;
Relids child_relids = child_rel->relids;
int i;
/*
* EC merging should be complete already, so we can use the parent rel's
* eclass_indexes to avoid searching all of root->eq_classes.
*/
Assert(root->ec_merging_done);
Assert(IS_SIMPLE_REL(parent_rel));
i = -1;
while ((i = bms_next_member(parent_rel->eclass_indexes, i)) >= 0)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
int num_members;
/*
* If this EC contains a volatile expression, then generating child
* EMs would be downright dangerous, so skip it. We rely on a
* volatile EC having only one EM.
*/
if (cur_ec->ec_has_volatile)
continue;
/* Sanity check eclass_indexes only contain ECs for parent_rel */
Assert(bms_is_subset(top_parent_relids, cur_ec->ec_relids));
/*
* We don't use foreach() here because there's no point in scanning
* newly-added child members, so we can stop after the last
* pre-existing EC member.
*/
num_members = list_length(cur_ec->ec_members);
for (int pos = 0; pos < num_members; pos++)
{
EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
if (cur_em->em_is_const)
continue; /* ignore consts here */
/*
* We consider only original EC members here, not
* already-transformed child members. Otherwise, if some original
* member expression references more than one appendrel, we'd get
* an O(N^2) explosion of useless derived expressions for
* combinations of children. (But add_child_join_rel_equivalences
* may add targeted combinations for partitionwise-join purposes.)
*/
if (cur_em->em_is_child)
continue; /* ignore children here */
/* Does this member reference child's topmost parent rel? */
if (bms_overlap(cur_em->em_relids, top_parent_relids))
{
/* Yes, generate transformed child version */
Expr *child_expr;
Relids new_relids;
Relids new_nullable_relids;
if (parent_rel->reloptkind == RELOPT_BASEREL)
{
/* Simple single-level transformation */
child_expr = (Expr *)
adjust_appendrel_attrs(root,
(Node *) cur_em->em_expr,
1, &appinfo);
}
else
{
/* Must do multi-level transformation */
child_expr = (Expr *)
adjust_appendrel_attrs_multilevel(root,
(Node *) cur_em->em_expr,
child_relids,
top_parent_relids);
}
/*
* Transform em_relids to match. Note we do *not* do
* pull_varnos(child_expr) here, as for example the
* transformation might have substituted a constant, but we
* don't want the child member to be marked as constant.
*/
new_relids = bms_difference(cur_em->em_relids,
top_parent_relids);
new_relids = bms_add_members(new_relids, child_relids);
/*
* And likewise for nullable_relids. Note this code assumes
* parent and child relids are singletons.
*/
new_nullable_relids = cur_em->em_nullable_relids;
if (bms_overlap(new_nullable_relids, top_parent_relids))
{
new_nullable_relids = bms_difference(new_nullable_relids,
top_parent_relids);
new_nullable_relids = bms_add_members(new_nullable_relids,
child_relids);
}
(void) add_eq_member(cur_ec, child_expr,
new_relids, new_nullable_relids,
true, cur_em->em_datatype);
/* Record this EC index for the child rel */
child_rel->eclass_indexes = bms_add_member(child_rel->eclass_indexes, i);
}
}
}
}
/*
* add_child_join_rel_equivalences
* Like add_child_rel_equivalences(), but for joinrels
*
* Here we find the ECs relevant to the top parent joinrel and add transformed
* member expressions that refer to this child joinrel.
*
* Note that this function won't be called at all unless we have at least some
* reason to believe that the EC members it generates will be useful.
*/
void
add_child_join_rel_equivalences(PlannerInfo *root,
int nappinfos, AppendRelInfo **appinfos,
RelOptInfo *parent_joinrel,
RelOptInfo *child_joinrel)
{
Relids top_parent_relids = child_joinrel->top_parent_relids;
Relids child_relids = child_joinrel->relids;
Bitmapset *matching_ecs;
MemoryContext oldcontext;
int i;
Assert(IS_JOIN_REL(child_joinrel) && IS_JOIN_REL(parent_joinrel));
/* We need consider only ECs that mention the parent joinrel */
matching_ecs = get_eclass_indexes_for_relids(root, top_parent_relids);
/*
* If we're being called during GEQO join planning, we still have to
* create any new EC members in the main planner context, to avoid having
* a corrupt EC data structure after the GEQO context is reset. This is
* problematic since we'll leak memory across repeated GEQO cycles. For
* now, though, bloat is better than crash. If it becomes a real issue
* we'll have to do something to avoid generating duplicate EC members.
*/
oldcontext = MemoryContextSwitchTo(root->planner_cxt);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
int num_members;
/*
* If this EC contains a volatile expression, then generating child
* EMs would be downright dangerous, so skip it. We rely on a
* volatile EC having only one EM.
*/
if (cur_ec->ec_has_volatile)
continue;
/* Sanity check on get_eclass_indexes_for_relids result */
Assert(bms_overlap(top_parent_relids, cur_ec->ec_relids));
/*
* We don't use foreach() here because there's no point in scanning
* newly-added child members, so we can stop after the last
* pre-existing EC member.
*/
num_members = list_length(cur_ec->ec_members);
for (int pos = 0; pos < num_members; pos++)
{
EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
if (cur_em->em_is_const)
continue; /* ignore consts here */
/*
* We consider only original EC members here, not
* already-transformed child members.
*/
if (cur_em->em_is_child)
continue; /* ignore children here */
/*
* We may ignore expressions that reference a single baserel,
* because add_child_rel_equivalences should have handled them.
*/
if (bms_membership(cur_em->em_relids) != BMS_MULTIPLE)
continue;
/* Does this member reference child's topmost parent rel? */
if (bms_overlap(cur_em->em_relids, top_parent_relids))
{
/* Yes, generate transformed child version */
Expr *child_expr;
Relids new_relids;
Relids new_nullable_relids;
if (parent_joinrel->reloptkind == RELOPT_JOINREL)
{
/* Simple single-level transformation */
child_expr = (Expr *)
adjust_appendrel_attrs(root,
(Node *) cur_em->em_expr,
nappinfos, appinfos);
}
else
{
/* Must do multi-level transformation */
Assert(parent_joinrel->reloptkind == RELOPT_OTHER_JOINREL);
child_expr = (Expr *)
adjust_appendrel_attrs_multilevel(root,
(Node *) cur_em->em_expr,
child_relids,
top_parent_relids);
}
/*
* Transform em_relids to match. Note we do *not* do
* pull_varnos(child_expr) here, as for example the
* transformation might have substituted a constant, but we
* don't want the child member to be marked as constant.
*/
new_relids = bms_difference(cur_em->em_relids,
top_parent_relids);
new_relids = bms_add_members(new_relids, child_relids);
/*
* For nullable_relids, we must selectively replace parent
* nullable relids with child ones.
*/
new_nullable_relids = cur_em->em_nullable_relids;
if (bms_overlap(new_nullable_relids, top_parent_relids))
new_nullable_relids =
adjust_child_relids_multilevel(root,
new_nullable_relids,
child_relids,
top_parent_relids);
(void) add_eq_member(cur_ec, child_expr,
new_relids, new_nullable_relids,
true, cur_em->em_datatype);
}
}
}
MemoryContextSwitchTo(oldcontext);
}
/*
* generate_implied_equalities_for_column
* Create EC-derived joinclauses usable with a specific column.
*
* This is used by indxpath.c to extract potentially indexable joinclauses
* from ECs, and can be used by foreign data wrappers for similar purposes.
* We assume that only expressions in Vars of a single table are of interest,
* but the caller provides a callback function to identify exactly which
* such expressions it would like to know about.
*
* We assume that any given table/index column could appear in only one EC.
* (This should be true in all but the most pathological cases, and if it
* isn't, we stop on the first match anyway.) Therefore, what we return
* is a redundant list of clauses equating the table/index column to each of
* the other-relation values it is known to be equal to. Any one of
* these clauses can be used to create a parameterized path, and there
* is no value in using more than one. (But it *is* worthwhile to create
* a separate parameterized path for each one, since that leads to different
* join orders.)
*
* The caller can pass a Relids set of rels we aren't interested in joining
* to, so as to save the work of creating useless clauses.
*/
List *
generate_implied_equalities_for_column(PlannerInfo *root,
RelOptInfo *rel,
ec_matches_callback_type callback,
void *callback_arg,
Relids prohibited_rels)
{
List *result = NIL;
bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
Relids parent_relids;
int i;
/* Should be OK to rely on eclass_indexes */
Assert(root->ec_merging_done);
/* Indexes are available only on base or "other" member relations. */
Assert(IS_SIMPLE_REL(rel));
/* If it's a child rel, we'll need to know what its parent(s) are */
if (is_child_rel)
parent_relids = find_childrel_parents(root, rel);
else
parent_relids = NULL; /* not used, but keep compiler quiet */
i = -1;
while ((i = bms_next_member(rel->eclass_indexes, i)) >= 0)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
EquivalenceMember *cur_em;
ListCell *lc2;
/* Sanity check eclass_indexes only contain ECs for rel */
Assert(is_child_rel || bms_is_subset(rel->relids, cur_ec->ec_relids));
/*
* Won't generate joinclauses if const or single-member (the latter
* test covers the volatile case too)
*/
if (cur_ec->ec_has_const || list_length(cur_ec->ec_members) <= 1)
continue;
/*
* Scan members, looking for a match to the target column. Note that
* child EC members are considered, but only when they belong to the
* target relation. (Unlike regular members, the same expression
* could be a child member of more than one EC. Therefore, it's
* potentially order-dependent which EC a child relation's target
* column gets matched to. This is annoying but it only happens in
* corner cases, so for now we live with just reporting the first
* match. See also get_eclass_for_sort_expr.)
*/
cur_em = NULL;
foreach(lc2, cur_ec->ec_members)
{
cur_em = (EquivalenceMember *) lfirst(lc2);
if (bms_equal(cur_em->em_relids, rel->relids) &&
callback(root, rel, cur_ec, cur_em, callback_arg))
break;
cur_em = NULL;
}
if (!cur_em)
continue;
/*
* Found our match. Scan the other EC members and attempt to generate
* joinclauses.
*/
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *other_em = (EquivalenceMember *) lfirst(lc2);
Oid eq_op;
RestrictInfo *rinfo;
if (other_em->em_is_child)
continue; /* ignore children here */
/* Make sure it'll be a join to a different rel */
if (other_em == cur_em ||
bms_overlap(other_em->em_relids, rel->relids))
continue;
/* Forget it if caller doesn't want joins to this rel */
if (bms_overlap(other_em->em_relids, prohibited_rels))
continue;
/*
* Also, if this is a child rel, avoid generating a useless join
* to its parent rel(s).
*/
if (is_child_rel &&
bms_overlap(parent_relids, other_em->em_relids))
continue;
eq_op = select_equality_operator(cur_ec,
cur_em->em_datatype,
other_em->em_datatype);
if (!OidIsValid(eq_op))
continue;
/* set parent_ec to mark as redundant with other joinclauses */
rinfo = create_join_clause(root, cur_ec, eq_op,
cur_em, other_em,
cur_ec);
result = lappend(result, rinfo);
}
/*
* If somehow we failed to create any join clauses, we might as well
* keep scanning the ECs for another match. But if we did make any,
* we're done, because we don't want to return non-redundant clauses.
*/
if (result)
break;
}
return result;
}
/*
* have_relevant_eclass_joinclause
* Detect whether there is an EquivalenceClass that could produce
* a joinclause involving the two given relations.
*
* This is essentially a very cut-down version of
* generate_join_implied_equalities(). Note it's OK to occasionally say "yes"
* incorrectly. Hence we don't bother with details like whether the lack of a
* cross-type operator might prevent the clause from actually being generated.
*/
bool
have_relevant_eclass_joinclause(PlannerInfo *root,
RelOptInfo *rel1, RelOptInfo *rel2)
{
Bitmapset *matching_ecs;
int i;
/* Examine only eclasses mentioning both rel1 and rel2 */
matching_ecs = get_common_eclass_indexes(root, rel1->relids,
rel2->relids);
i = -1;
while ((i = bms_next_member(matching_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
i);
/*
* Sanity check that get_common_eclass_indexes gave only ECs
* containing both rels.
*/
Assert(bms_overlap(rel1->relids, ec->ec_relids));
Assert(bms_overlap(rel2->relids, ec->ec_relids));
/*
* Won't generate joinclauses if single-member (this test covers the
* volatile case too)
*/
if (list_length(ec->ec_members) <= 1)
continue;
/*
* We do not need to examine the individual members of the EC, because
* all that we care about is whether each rel overlaps the relids of
* at least one member, and get_common_eclass_indexes() and the single
* member check above are sufficient to prove that. (As with
* have_relevant_joinclause(), it is not necessary that the EC be able
* to form a joinclause relating exactly the two given rels, only that
* it be able to form a joinclause mentioning both, and this will
* surely be true if both of them overlap ec_relids.)
*
* Note we don't test ec_broken; if we did, we'd need a separate code
* path to look through ec_sources. Checking the membership anyway is
* OK as a possibly-overoptimistic heuristic.
*
* We don't test ec_has_const either, even though a const eclass won't
* generate real join clauses. This is because if we had "WHERE a.x =
* b.y and a.x = 42", it is worth considering a join between a and b,
* since the join result is likely to be small even though it'll end
* up being an unqualified nestloop.
*/
return true;
}
return false;
}
/*
* has_relevant_eclass_joinclause
* Detect whether there is an EquivalenceClass that could produce
* a joinclause involving the given relation and anything else.
*
* This is the same as have_relevant_eclass_joinclause with the other rel
* implicitly defined as "everything else in the query".
*/
bool
has_relevant_eclass_joinclause(PlannerInfo *root, RelOptInfo *rel1)
{
Bitmapset *matched_ecs;
int i;
/* Examine only eclasses mentioning rel1 */
matched_ecs = get_eclass_indexes_for_relids(root, rel1->relids);
i = -1;
while ((i = bms_next_member(matched_ecs, i)) >= 0)
{
EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
i);
/*
* Won't generate joinclauses if single-member (this test covers the
* volatile case too)
*/
if (list_length(ec->ec_members) <= 1)
continue;
/*
* Per the comment in have_relevant_eclass_joinclause, it's sufficient
* to find an EC that mentions both this rel and some other rel.
*/
if (!bms_is_subset(ec->ec_relids, rel1->relids))
return true;
}
return false;
}
/*
* eclass_useful_for_merging
* Detect whether the EC could produce any mergejoinable join clauses
* against the specified relation.
*
* This is just a heuristic test and doesn't have to be exact; it's better
* to say "yes" incorrectly than "no". Hence we don't bother with details
* like whether the lack of a cross-type operator might prevent the clause
* from actually being generated.
*/
bool
eclass_useful_for_merging(PlannerInfo *root,
EquivalenceClass *eclass,
RelOptInfo *rel)
{
Relids relids;
ListCell *lc;
Assert(!eclass->ec_merged);
/*
* Won't generate joinclauses if const or single-member (the latter test
* covers the volatile case too)
*/
if (eclass->ec_has_const || list_length(eclass->ec_members) <= 1)
return false;
/*
* Note we don't test ec_broken; if we did, we'd need a separate code path
* to look through ec_sources. Checking the members anyway is OK as a
* possibly-overoptimistic heuristic.
*/
/* If specified rel is a child, we must consider the topmost parent rel */
if (IS_OTHER_REL(rel))
{
Assert(!bms_is_empty(rel->top_parent_relids));
relids = rel->top_parent_relids;
}
else
relids = rel->relids;
/* If rel already includes all members of eclass, no point in searching */
if (bms_is_subset(eclass->ec_relids, relids))
return false;
/* To join, we need a member not in the given rel */
foreach(lc, eclass->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
if (cur_em->em_is_child)
continue; /* ignore children here */
if (!bms_overlap(cur_em->em_relids, relids))
return true;
}
return false;
}
/*
* is_redundant_derived_clause
* Test whether rinfo is derived from same EC as any clause in clauselist;
* if so, it can be presumed to represent a condition that's redundant
* with that member of the list.
*/
bool
is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist)
{
EquivalenceClass *parent_ec = rinfo->parent_ec;
ListCell *lc;
/* Fail if it's not a potentially-redundant clause from some EC */
if (parent_ec == NULL)
return false;
foreach(lc, clauselist)
{
RestrictInfo *otherrinfo = (RestrictInfo *) lfirst(lc);
if (otherrinfo->parent_ec == parent_ec)
return true;
}
return false;
}
/*
* translate_expr_to_rel_vars
* If the appropriate equivalence classes exist, replace vars in
* gvi->gvexpr with vars whose varno is equal to relid. Return NULL if
* translation is not possible or needed.
*
* Note: Currently we only translate Var expressions. This is subject to
* change as the aggregate push-down feature gets enhanced.
*/
GroupedVarInfo *
translate_expr_to_rel_vars(PlannerInfo *root, GroupedVarInfo *gvi,
Index relid)
{
Var *var;
ListCell *l1;
bool found_orig = false;
Var *var_translated = NULL;
GroupedVarInfo *result;
/* Can't do anything w/o equivalence classes. */
if (root->eq_classes == NIL)
return NULL;
/* Now we only support simple Var translate. */
if (!IsA(gvi->gvexpr, Var))
return NULL;
var = castNode(Var, gvi->gvexpr);
/* Do we need to translate the var? */
if (var->varno == relid)
return NULL;
/* Find the replacement var. */
foreach(l1, root->eq_classes)
{
EquivalenceClass *ec = lfirst_node(EquivalenceClass, l1);
ListCell *l2;
/* These EC kind should be ignored. */
if (ec->ec_has_volatile || ec->ec_below_outer_join || ec->ec_broken)
continue;
/* Single-element EC can hardly help in translations. */
if (list_length(ec->ec_members) == 1)
continue;
/*
* Collect all vars of this EC and their varnos.
*
* ec->ec_relids does not help because we're only interested in a
* subset of EC members.
*/
foreach(l2, ec->ec_members)
{
EquivalenceMember *em = lfirst_node(EquivalenceMember, l2);
Var *ec_var;
/*
* The grouping expressions derived here are used to evaluate
* possibility to push aggregation down to RELOPT_BASEREL or
* RELOPT_JOINREL relations, and to construct reltargets for the
* grouped rels. We're not interested at the moment whether the
* relations do have children.
*/
if (em->em_is_child)
continue;
if (!IsA(em->em_expr, Var))
continue;
ec_var = castNode(Var, em->em_expr);
if (equal(ec_var, var))
found_orig = true;
else if (ec_var->varno == relid)
var_translated = ec_var;
if (found_orig && var_translated)
{
/*
* The replacement Var must have the same data type, otherwise
* the values are not guaranteed to be grouped in the same way
* as values of the original Var.
*/
if (ec_var->vartype != var->vartype)
return NULL;
break;
}
}
if (found_orig)
{
/* The same expression probably does not exist in multiple ECs. */
if (var_translated == NULL)
return NULL;
else
break;
}
else
{
/* Vars of the requested relid can be in the next ECs too. */
var_translated = NULL;
}
}
if (!found_orig)
return NULL;
result = makeNode(GroupedVarInfo);
memcpy(result, gvi, sizeof(GroupedVarInfo));
result->gv_eval_at = bms_make_singleton(relid);
result->gvexpr = (Expr *) var_translated;
return result;
}
/*
* is_redundant_with_indexclauses
* Test whether rinfo is redundant with any clause in the IndexClause
* list. Here, for convenience, we test both simple identity and
* whether it is derived from the same EC as any member of the list.
*/
bool
is_redundant_with_indexclauses(RestrictInfo *rinfo, List *indexclauses)
{
EquivalenceClass *parent_ec = rinfo->parent_ec;
ListCell *lc;
foreach(lc, indexclauses)
{
IndexClause *iclause = lfirst_node(IndexClause, lc);
RestrictInfo *otherrinfo = iclause->rinfo;
/* If indexclause is lossy, it won't enforce the condition exactly */
if (iclause->lossy)
continue;
/* Match if it's same clause (pointer equality should be enough) */
if (rinfo == otherrinfo)
return true;
/* Match if derived from same EC */
if (parent_ec && otherrinfo->parent_ec == parent_ec)
return true;
/*
* No need to look at the derived clauses in iclause->indexquals; they
* couldn't match if the parent clause didn't.
*/
}
return false;
}
/*
* get_eclass_indexes_for_relids
* Build and return a Bitmapset containing the indexes into root's
* eq_classes list for all eclasses that mention any of these relids
*/
static Bitmapset *
get_eclass_indexes_for_relids(PlannerInfo *root, Relids relids)
{
Bitmapset *ec_indexes = NULL;
int i = -1;
/* Should be OK to rely on eclass_indexes */
Assert(root->ec_merging_done);
while ((i = bms_next_member(relids, i)) > 0)
{
RelOptInfo *rel = root->simple_rel_array[i];
ec_indexes = bms_add_members(ec_indexes, rel->eclass_indexes);
}
return ec_indexes;
}
/*
* get_common_eclass_indexes
* Build and return a Bitmapset containing the indexes into root's
* eq_classes list for all eclasses that mention rels in both
* relids1 and relids2.
*/
static Bitmapset *
get_common_eclass_indexes(PlannerInfo *root, Relids relids1, Relids relids2)
{
Bitmapset *rel1ecs;
Bitmapset *rel2ecs;
int relid;
rel1ecs = get_eclass_indexes_for_relids(root, relids1);
/*
* We can get away with just using the relation's eclass_indexes directly
* when relids2 is a singleton set.
*/
if (bms_get_singleton_member(relids2, &relid))
rel2ecs = root->simple_rel_array[relid]->eclass_indexes;
else
rel2ecs = get_eclass_indexes_for_relids(root, relids2);
/* Calculate and return the common EC indexes, recycling the left input. */
return bms_int_members(rel1ecs, rel2ecs);
}