*
* equivclass.cpp
* Routines for managing EquivalenceClasses
*
* Portions Copyright (c) 2020 Huawei Technologies Co.,Ltd.
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/gausskernel/optimizer/path/equivclass.cpp
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "knl/knl_variable.h"
#include "access/skey.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "optimizer/subselect.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
#include "parser/parse_coerce.h"
#include "utils/lsyscache.h"
#ifdef PGXC
#include "pgxc/pgxc.h"
#endif
static EquivalenceMember* add_eq_member(
EquivalenceClass* ec, Expr* expr, Relids relids, Relids nullable_relids, bool is_child, Oid datatype);
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);
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, AppendRelInfo* inner_appinfo);
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 void generate_base_implied_quality_clause(PlannerInfo* root, RelOptInfo* rel, RestrictInfo* rinfo);
* 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. Returns TRUE if successful, FALSE if not (in which
* case caller should treat the clause as ordinary, not an equivalence).
*
* 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 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* restrictinfo, bool below_outer_join)
{
Expr* clause = restrictinfo->clause;
Oid opno, collation, item1_type, item2_type;
Expr* item1 = NULL;
Expr* item2 = NULL;
Relids item1_relids, item2_relids, item1_nullable_relids, item2_nullable_relids;
List* opfamilies = NIL;
EquivalenceClass* ec1 = NULL;
EquivalenceClass* ec2 = NULL;
EquivalenceMember* em1 = NULL;
EquivalenceMember* em2 = NULL;
ListCell* lc1 = NULL;
AssertEreport(restrictinfo->left_ec == NULL, MOD_OPT, "");
AssertEreport(restrictinfo->right_ec == NULL, MOD_OPT, "");
if (restrictinfo->security_level > 0 && !restrictinfo->leakproof)
return false;
AssertEreport(is_opclause(clause), MOD_OPT, "");
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);
* Reject clauses of the form X=X. These are not as redundant as they
* might seem at first glance: assuming the operator is strict, this is
* really an expensive way to write X IS NOT NULL. So we must not risk
* just losing the clause, which would be possible if there is already a
* single-element EquivalenceClass containing X. The case is not common
* enough to be worth contorting the EC machinery for, so just reject the
* clause and let it be processed as a normal restriction clause.
*/
if (equal(item1, item2))
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;
if (!bms_is_empty(item2_relids) && contain_nonstrict_functions((Node*)item2))
return false;
}
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;
foreach (lc1, root->eq_classes) {
EquivalenceClass* cur_ec = (EquivalenceClass*)lfirst(lc1);
ListCell* lc2 = NULL;
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);
AssertEreport(!cur_em->em_is_child, MOD_OPT, "");
* 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 == NULL && item1_type == cur_em->em_datatype && equal(item1, cur_em->em_expr)) {
ec1 = cur_ec;
em1 = cur_em;
if (ec2 != NULL)
break;
}
if (ec2 == NULL && item2_type == cur_em->em_datatype && equal(item2, cur_em->em_expr)) {
ec2 = cur_ec;
em2 = cur_em;
if (ec1 != NULL)
break;
}
}
if (ec1 != NULL && ec2 != NULL)
break;
}
if (ec1 != NULL && ec2 != NULL) {
if (ec1 == ec2) {
ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
ec1->ec_below_outer_join = 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);
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
return true;
}
* Case 2: need to merge ec1 and ec2. 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 = ec1->ec_has_const || ec2->ec_has_const;
ec1->ec_below_outer_join = 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_ptr(root->eq_classes, ec2);
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 = 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);
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
} else if (ec1 != NULL) {
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 = 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);
restrictinfo->left_ec = ec1;
restrictinfo->right_ec = ec1;
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
} else if (ec2 != NULL) {
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 = 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);
restrictinfo->left_ec = ec2;
restrictinfo->right_ec = ec2;
restrictinfo->left_em = em1;
restrictinfo->right_em = em2;
} else {
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);
restrictinfo->left_ec = ec;
restrictinfo->right_ec = ec;
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.)
*
* Note this code assumes that the expression has already been through
* eval_const_expressions, so there are no CollateExprs and no redundant
* RelabelTypes.
*/
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.
*/
if (IsPolymorphicType(req_type))
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) {
* Strip any existing RelabelType, then add a new one if needed. This
* is to preserve the invariant of no redundant RelabelTypes.
*
* If we have to change the exposed type of the stripped expression,
* set typmod to -1 (since the new type may not have the same typmod
* interpretation). If we only have to change collation, preserve the
* exposed typmod.
*/
while (expr && IsA(expr, RelabelType))
expr = (Expr*)((RelabelType*)expr)->arg;
if (exprType((Node*)expr) != req_type)
expr = (Expr*)makeRelabelType(expr, req_type, -1, req_collation, COERCE_DONTCARE);
else if (exprCollation((Node*)expr) != req_collation)
expr = (Expr*)makeRelabelType(expr, req_type, exprTypmod((Node*)expr), req_collation, COERCE_DONTCARE);
}
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.
*/
AssertEreport(!is_child, MOD_OPT, "");
em->em_is_const = true;
ec->ec_has_const = true;
} else if (!is_child) {
ec->ec_relids = bms_add_members(ec->ec_relids, relids);
}
ec->ec_members = lappend(ec->ec_members, em);
return em;
}
static bool restrict_contains_bplike_walker(Node *node, void *context)
{
if (node == NULL) {
return false;
}
if (IsA(node, OpExpr)) {
OpExpr *opExpr = (OpExpr *)node;
if (opExpr->opno == OID_BPCHAR_LIKE_OP || opExpr->opno == OID_BPCHAR_NOT_LIKE_OP ||
opExpr->opno == OID_BPCHAR_ICLIKE_OP || opExpr->opno == OID_BPCHAR_IC_NOT_LIKE_OP) {
return true;
}
}
return expression_tree_walker(node, (bool (*)())restrict_contains_bplike_walker, context);
}
static bool restrict_contains_bplike(RestrictInfo *rinfo)
{
return restrict_contains_bplike_walker((Node *)rinfo->clause, NULL);
}
* get_eclass_for_sort_expr
* Given an expression and opfamily/collation info, find an existing
* equivalence class it is a member of; if none, optionally build a new
* single-member EquivalenceClass for it.
*
* sortref is the SortGroupRef of the originating SortGroupClause, if any,
* or zero if not. (It should never be zero if the expression is volatile!)
*
* If rel is not NULL, it identifies a specific relation we're considering
* a path for, and indicates that child EC members for that relation can be
* considered. Otherwise child members are ignored. (Note: since child EC
* members aren't guaranteed unique, a non-NULL value means that there could
* be more than one EC that matches the expression; if so it's order-dependent
* which one you get. This is annoying but it only happens in corner cases,
* so for now we live with just reporting the first match. See also
* generate_implied_equalities_for_indexcol and match_pathkeys_to_index.)
*
* If create_it is TRUE, we'll build a new EquivalenceClass when there is no
* match. If create_it is FALSE, we just return NULL when no match.
*
* This can be used safely both before and after EquivalenceClass merging;
* since it never causes merging it does not invalidate any existing ECs
* or PathKeys. However, ECs added after path generation has begun are
* of limited usefulness, so usually it's best to create them beforehand.
*
* Note: opfamilies must be chosen consistently with the way
* process_equivalence() would do; that is, generated from a mergejoinable
* equality operator. Else we might fail to detect valid equivalences,
* generating poor (but not incorrect) plans.
*/
EquivalenceClass* get_eclass_for_sort_expr(PlannerInfo* root, Expr* expr, List* opfamilies, Oid opcintype,
Oid collation, Index sortref, bool groupSet, Relids rel, bool create_it)
{
EquivalenceClass* newec = NULL;
EquivalenceMember* newem = NULL;
ListCell* lc1 = NULL;
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 = NULL;
* 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 (cur_ec->ec_group_set != groupSet)
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;
}
}
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_group_set = groupSet;
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)
ereport(ERROR,
(errmodule(MOD_OPT),
errcode(ERRCODE_OPTIMIZER_INCONSISTENT_STATE),
(errmsg("volatile EquivalenceClass has no sortref"))));
newem = add_eq_member(newec, (Expr*)copyObject(expr), pull_varnos((Node*)expr), NULL, 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);
(void)MemoryContextSwitchTo(oldcontext);
return newec;
}
* generate_base_implied_qualities
* Generate any restriction clauses that we can deduce from equivalence classes.
*/
void generate_base_implied_qualities(PlannerInfo* root)
{
int relSN = 0;
int infoLen = 0;
ListCell* cell = NULL;
for (relSN = 1; relSN < root->simple_rel_array_size; relSN++) {
RelOptInfo* rel = root->simple_rel_array[relSN];
if (rel == NULL || rel->reloptkind != RELOPT_BASEREL)
continue;
infoLen = list_length(rel->baserestrictinfo);
foreach (cell, rel->baserestrictinfo) {
RestrictInfo* rinfo = (RestrictInfo*)lfirst(cell);
List* subplan_list = NIL;
if (--infoLen < 0)
continue;
if (rinfo->pseudoconstant)
continue;
if (!bms_is_empty(rinfo->outer_relids))
continue;
if (contain_volatile_functions((Node*)rinfo->clause))
continue;
if ((subplan_list = check_subplan_expr((Node*)rinfo->clause)) != NIL) {
list_free_ext(subplan_list);
continue;
}
if (rinfo->outerjoin_delayed)
continue;
if (!rinfo->is_pushed_down)
continue;
if (rinfo->can_join)
continue;
if (!bms_is_empty(rinfo->nullable_relids))
continue;
if (!bms_equal(rinfo->required_relids, rinfo->clause_relids))
continue;
if (BMS_SINGLETON != bms_membership(rinfo->clause_relids))
continue;
* Even two vars are in the same EquivalenceClass, there exists some expression get different result on two
* vars. The type bpchar (blank padded character) is an example. Its equal function and like function is not
* consistent.
* equal function---bpchareq: ignore the padded blank charater at the end of the Var.
* like function --bpliketext: NOT ignore the padded blank character!
* For example:
* create table A(a char(10)); create table B(a char(2));
* insert into A values('33'); insert into B values('33');
* Then A.a = B.a, but B.a like '33' is true while A.a like '33' is false !.
*
* This is the only inconsistent behavior among EquivalenceClass members we found yet. So just skip it!
*/
if (restrict_contains_bplike(rinfo)) {
continue;
}
generate_base_implied_quality_clause(root, rel, rinfo);
}
}
}
static void generate_base_implied_quality_clause(PlannerInfo* root, RelOptInfo* rel, RestrictInfo* rinfo)
{
ListCell* em_cell = NULL;
ListCell* ec_cell = NULL;
foreach (ec_cell, root->eq_classes) {
EquivalenceClass* ec = (EquivalenceClass*)lfirst(ec_cell);
List* src_list = NIL;
if (list_length(ec->ec_members) <= 1 || ec->ec_has_volatile ||
!bms_is_subset(rinfo->clause_relids, ec->ec_relids))
continue;
foreach (em_cell, ec->ec_members) {
EquivalenceMember* em = (EquivalenceMember*)lfirst(em_cell);
if (equal(em->em_expr, rinfo->clause))
continue;
if (em->em_is_const)
continue;
if (!bms_is_subset(em->em_relids, rinfo->clause_relids))
continue;
if (check_node_clause((Node*)rinfo->clause, (Node*)em->em_expr))
src_list = lappend(src_list, em->em_expr);
}
if (NIL == src_list)
continue;
foreach (em_cell, ec->ec_members) {
EquivalenceMember* em = (EquivalenceMember*)lfirst(em_cell);
Node* new_clause = NULL;
Relids relids = NULL;
if (BMS_SINGLETON != bms_membership(em->em_relids))
continue;
if (bms_equal(em->em_relids, rinfo->clause_relids))
continue;
if (list_member(src_list, em->em_expr))
continue;
if (IsA((Node*)rinfo->clause, NullTest) && ((NullTest*)rinfo->clause)->nulltesttype == IS_NOT_NULL &&
check_var_nonnullable(root->parse, (Node*)em->em_expr)) {
continue;
}
new_clause = replace_node_clause_for_equality((Node*)rinfo->clause, src_list, (Node*)em->em_expr);
relids = pull_varnos(new_clause);
if (!bms_equal(relids, em->em_relids))
continue;
process_implied_quality(root, new_clause, bms_copy(em->em_relids), ec->ec_below_outer_join);
}
list_free_ext(src_list);
}
}
* generate_base_implied_equalities
* Generate any restriction clauses that we can deduce from equivalence
* classes.
*
* When an EC contains pseudoconstants, our strategy is to generate
* "member = const1" clauses where const1 is the first constant member, for
* every other member (including other constants). If we are able to do this
* then we don't need any "var = var" comparisons because we've successfully
* constrained all the vars at their points of creation. If we fail to
* generate any of these clauses due to lack of cross-type operators, we fall
* back to the "ec_broken" strategy described below. (XXX if there are
* multiple constants of different types, it's possible that we might succeed
* in forming all the required clauses if we started from a different const
* member; but this seems a sufficiently hokey corner case to not be worth
* spending lots of cycles on.)
*
* For ECs that contain no pseudoconstants, we generate derived clauses
* "member1 = member2" for each pair of members belonging to the same base
* relation (actually, if there are more than two for the same base relation,
* we only need enough clauses to link each to each other). This provides
* the base case for the recursion: each row emitted by a base relation scan
* will constrain all computable members of the EC to be equal. As each
* join path is formed, we'll add additional derived clauses on-the-fly
* to maintain this invariant (see generate_join_implied_equalities).
*
* If the opfamilies used by the EC do not provide complete sets of cross-type
* equality operators, it is possible that we will fail to generate a clause
* that must be generated to maintain the invariant. (An example: given
* "WHERE a.x = b.y AND b.y = a.z", the scheme breaks down if we cannot
* generate "a.x = a.z" as a restriction clause for A.) In this case we mark
* the EC "ec_broken" and fall back to regurgitating its original source
* RestrictInfos at appropriate times. We do not try to retract any derived
* clauses already generated from the broken EC, so the resulting plan could
* be poor due to bad selectivity estimates caused by redundant clauses. But
* the correct solution to that is to fix the opfamilies ...
*
* Equality clauses derived by this function are passed off to
* process_implied_equality (in plan/initsplan.c) to be inserted into the
* restrictinfo datastructures. Note that this must be called after initial
* scanning of the quals and before Path construction begins.
*
* We make no attempt to avoid generating duplicate RestrictInfos here: we
* don't search ec_sources for matches, nor put the created RestrictInfos
* into ec_derives. Doing so would require some slightly ugly changes in
* initsplan.c's API, and there's no real advantage, because the clauses
* generated here can't duplicate anything we will generate for joins anyway.
*/
void generate_base_implied_equalities(PlannerInfo* root)
{
ListCell* lc = NULL;
int rti;
foreach (lc, root->eq_classes) {
EquivalenceClass* ec = (EquivalenceClass*)lfirst(lc);
AssertEreport(ec->ec_merged == NULL, MOD_OPT, "");
AssertEreport(!ec->ec_broken, MOD_OPT, "");
if (list_length(ec->ec_members) <= 1)
continue;
if (ec->ec_has_const)
generate_base_implied_equalities_const(root, ec);
else
generate_base_implied_equalities_no_const(root, ec);
if (ec->ec_broken)
generate_base_implied_equalities_broken(root, ec);
}
* This is also a handy place to mark base rels (which should all exist by
* now) with flags showing whether they have pending eclass joins.
*/
for (rti = 1; rti < root->simple_rel_array_size; rti++) {
RelOptInfo* brel = root->simple_rel_array[rti];
if (brel == NULL)
continue;
brel->has_eclass_joins = has_relevant_eclass_joinclause(root, brel);
}
}
* generate_base_implied_equalities when EC contains pseudoconstant(s)
*/
static void generate_base_implied_equalities_const(PlannerInfo* root, EquivalenceClass* ec)
{
EquivalenceMember* const_em = NULL;
ListCell* lc = NULL;
* 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;
}
}
AssertEreport(const_em != NULL, MOD_OPT, "");
foreach (lc, ec->ec_members) {
EquivalenceMember* cur_em = (EquivalenceMember*)lfirst(lc);
Oid eq_op;
AssertEreport(!cur_em->em_is_child, MOD_OPT, "");
if (cur_em == const_em)
continue;
eq_op = select_equality_operator(ec, cur_em->em_datatype, const_em->em_datatype);
if (!OidIsValid(eq_op)) {
ec->ec_broken = true;
break;
}
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);
}
}
* 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 = NULL;
* We scan the EC members once and track the last-seen member for each
* base relation. When we see another member of the same base relation,
* we generate "prev_mem = cur_mem". This results in the minimum number
* of derived clauses, but it's possible that it will fail when a
* different ordering would succeed.
*/
prev_ems = (EquivalenceMember**)palloc0(root->simple_rel_array_size * sizeof(EquivalenceMember*));
foreach (lc, ec->ec_members) {
EquivalenceMember* cur_em = (EquivalenceMember*)lfirst(lc);
int relid;
AssertEreport(!cur_em->em_is_child, MOD_OPT, "");
if (bms_membership(cur_em->em_relids) != BMS_SINGLETON)
continue;
relid = bms_singleton_member(cur_em->em_relids);
AssertEreport(relid < root->simple_rel_array_size, MOD_OPT, "");
if (prev_ems[relid] != NULL) {
EquivalenceMember* prev_em = prev_ems[relid];
Oid eq_op;
eq_op = select_equality_operator(ec, prev_em->em_datatype, cur_em->em_datatype);
if (!OidIsValid(eq_op)) {
ec->ec_broken = true;
break;
}
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);
}
prev_ems[relid] = cur_em;
}
pfree_ext(prev_ems);
* We also have to make sure that all the Vars used in the member clauses
* will be available at any join node we might try to reference them at.
* For the moment we force all the Vars to be available at all join nodes
* for this eclass. Perhaps this could be improved by doing some
* pre-analysis of which members we prefer to join, but it's no worse than
* what happened in the pre-8.3 code.
*/
foreach (lc, ec->ec_members) {
EquivalenceMember* cur_em = (EquivalenceMember*)lfirst(lc);
List* vars = pull_var_clause((Node*)cur_em->em_expr, PVC_RECURSE_AGGREGATES, PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, ec->ec_relids, false);
list_free_ext(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 = NULL;
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)
{
return generate_join_implied_equalities_for_ecs(root, root->eq_classes, join_relids, outer_relids, inner_rel);
}
* 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;
AppendRelInfo* inner_appinfo = NULL;
ListCell* lc = NULL;
if (inner_rel->reloptkind == RELOPT_OTHER_MEMBER_REL) {
inner_appinfo = find_childrel_appendrelinfo(root, inner_rel);
nominal_inner_relids = bms_make_singleton(inner_appinfo->parent_relid);
nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
} else {
inner_appinfo = NULL;
nominal_inner_relids = inner_relids;
nominal_join_relids = join_relids;
}
foreach (lc, eclasses) {
EquivalenceClass* ec = (EquivalenceClass*)lfirst(lc);
List* sublist = NIL;
bool checkAsof = false;
ListCell *jr = NULL;
foreach (jr, ec->ec_sources) {
RestrictInfo *ri = (RestrictInfo *)lfirst(jr);
if (ri->is_asof) {
checkAsof = true;
break;
}
}
#ifdef STREAMPLAN
if (!IS_STREAM_PLAN && ec->ec_has_const && !checkAsof)
continue;
#else
if (ec->ec_has_const && !checkAsof)
continue;
#endif
if (list_length(ec->ec_members) <= 1)
continue;
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);
if (ec->ec_broken)
sublist = generate_join_implied_equalities_broken(
root, ec, nominal_join_relids, outer_relids, nominal_inner_relids, inner_appinfo);
result = list_concat(result, sublist);
}
return result;
}
* generate_join_implied_equalities for a still-valid EC
*/
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 = NULL;
bool has_const = false;
bool check_asof = false;
ListCell *jr = NULL;
foreach (jr, ec->ec_sources) {
RestrictInfo *ri = (RestrictInfo *)lfirst(jr);
if (ri->is_asof) {
check_asof = true;
break;
}
}
* 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);
#ifdef STREAMPLAN
if (IS_STREAM_PLAN && cur_em->em_is_const && !check_asof) {
has_const = true;
continue;
}
#endif
* 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;
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 != NULL && inner_members != NULL) {
EquivalenceMember* best_outer_em = NULL;
EquivalenceMember* best_inner_em = NULL;
Oid best_eq_op = InvalidOid;
int best_score = -1;
RestrictInfo* rinfo = NULL;
foreach (lc1, outer_members) {
EquivalenceMember* outer_em = (EquivalenceMember*)lfirst(lc1);
ListCell* lc2 = NULL;
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;
}
}
if (best_score == 3)
break;
}
if (best_score < 0) {
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);
#ifdef STREAMPLAN
if (IS_STREAM_PLAN && has_const)
rinfo->pseudoconstant = true;
#endif
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 != NULL) {
List* old_members = list_concat(outer_members, inner_members);
EquivalenceMember* prev_em = NULL;
RestrictInfo* rinfo = NULL;
if (old_members != NULL)
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)) {
ec->ec_broken = true;
return NIL;
}
#ifdef STREAMPLAN
if (!has_const)
#endif
{
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, AppendRelInfo* inner_appinfo)
{
List* result = NIL;
ListCell* lc = NULL;
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.
*/
if (inner_appinfo != NULL)
result = (List*)adjust_appendrel_attrs(root, (Node*)result, inner_appinfo);
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 = NULL;
foreach (lc, ec->ec_opfamilies) {
Oid opfamily = lfirst_oid(lc);
Oid opno = get_opfamily_member(opfamily, lefttype, righttype, BTEqualStrategyNumber);
if (!OidIsValid(opno))
continue;
if (ec->ec_max_security == 0)
return opno;
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 = NULL;
ListCell* lc = NULL;
MemoryContext oldcontext;
* Search to see if we already built a RestrictInfo for this pair of
* EquivalenceMembers. We can use either original source clauses or
* previously-derived clauses. The check on opno is probably redundant,
* but be safe ...
*/
foreach (lc, ec->ec_sources) {
rinfo = (RestrictInfo*)lfirst(lc);
if (rinfo->left_em == leftem && rinfo->right_em == rightem && rinfo->parent_ec == parent_ec &&
opno == ((OpExpr*)rinfo->clause)->opno)
return rinfo;
}
foreach (lc, ec->ec_derives) {
rinfo = (RestrictInfo*)lfirst(lc);
if (rinfo->left_em == leftem && rinfo->right_em == rightem && rinfo->parent_ec == parent_ec &&
opno == ((OpExpr*)rinfo->clause)->opno)
return rinfo;
}
* Not there, so build it, in planner context so we can re-use it. (Not
* important in normal planning, but definitely so in GEQO.)
*/
oldcontext = MemoryContextSwitchTo(root->planner_cxt);
rinfo = build_implied_join_equality(opno,
ec->ec_collation,
leftem->em_expr,
rightem->em_expr,
bms_union(leftem->em_relids, rightem->em_relids),
bms_union(leftem->em_nullable_relids, rightem->em_nullable_relids),
ec->ec_min_security);
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;
rinfo->left_em = leftem;
rinfo->right_em = rightem;
ec->ec_derives = lappend(ec->ec_derives, rinfo);
(void)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 = false;
ListCell* cell = NULL;
ListCell* prev = NULL;
ListCell* next = NULL;
do {
found = false;
prev = NULL;
for (cell = list_head(root->left_join_clauses); cell; cell = next) {
RestrictInfo* rinfo = (RestrictInfo*)lfirst(cell);
next = lnext(cell);
if (reconsider_outer_join_clause(root, rinfo, true)) {
found = true;
root->left_join_clauses = list_delete_cell(root->left_join_clauses, cell, prev);
rinfo->norm_selec = 2.0;
rinfo->outer_selec = 1.0;
distribute_restrictinfo_to_rels(root, rinfo);
} else
prev = cell;
}
prev = NULL;
for (cell = list_head(root->right_join_clauses); cell; cell = next) {
RestrictInfo* rinfo = (RestrictInfo*)lfirst(cell);
next = lnext(cell);
if (reconsider_outer_join_clause(root, rinfo, false)) {
found = true;
root->right_join_clauses = list_delete_cell(root->right_join_clauses, cell, prev);
rinfo->norm_selec = 2.0;
rinfo->outer_selec = 1.0;
distribute_restrictinfo_to_rels(root, rinfo);
} else
prev = cell;
}
prev = NULL;
for (cell = list_head(root->full_join_clauses); cell; cell = next) {
RestrictInfo* rinfo = (RestrictInfo*)lfirst(cell);
next = lnext(cell);
if (reconsider_full_join_clause(root, rinfo)) {
found = true;
root->full_join_clauses = list_delete_cell(root->full_join_clauses, cell, prev);
rinfo->norm_selec = 2.0;
rinfo->outer_selec = 1.0;
distribute_restrictinfo_to_rels(root, rinfo);
} else
prev = cell;
}
} while (found);
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 = NULL;
Expr* innervar = NULL;
Oid opno, collation, left_type, right_type, inner_datatype;
Relids inner_relids, inner_nullable_relids;
ListCell* lc1 = NULL;
AssertEreport(is_opclause(rinfo->clause), MOD_OPT, "");
opno = ((OpExpr*)rinfo->clause)->opno;
collation = ((OpExpr*)rinfo->clause)->inputcollid;
if (rinfo->outerjoin_delayed && !op_strict(opno))
return false;
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);
foreach (lc1, root->eq_classes) {
EquivalenceClass* cur_ec = (EquivalenceClass*)lfirst(lc1);
bool match = false;
ListCell* lc2 = NULL;
if (!cur_ec->ec_has_const)
continue;
if (cur_ec->ec_has_volatile)
continue;
if (collation != cur_ec->ec_collation)
continue;
if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
continue;
foreach (lc2, cur_ec->ec_members) {
EquivalenceMember* cur_em = (EquivalenceMember*)lfirst(lc2);
AssertEreport(!cur_em->em_is_child, MOD_OPT, "");
if (equal(outervar, cur_em->em_expr)) {
match = true;
break;
}
}
if (!match)
continue;
* 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 = NULL;
if (!cur_em->em_is_const)
continue;
eq_op = select_equality_operator(cur_ec, inner_datatype, cur_em->em_datatype);
if (!OidIsValid(eq_op))
continue;
newrinfo = build_implied_join_equality(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;
}
* 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 = NULL;
Expr* rightvar = NULL;
Oid opno, collation, left_type, right_type;
Relids left_relids, right_relids, left_nullable_relids, right_nullable_relids;
ListCell* lc1 = NULL;
if (rinfo->outerjoin_delayed)
return false;
AssertEreport(is_opclause(rinfo->clause), MOD_OPT, "");
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 = false;
bool matchleft = false;
bool matchright = false;
ListCell* lc2 = NULL;
if (!cur_ec->ec_has_const)
continue;
if (cur_ec->ec_has_volatile)
continue;
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);
AssertEreport(!coal_em->em_is_child, MOD_OPT, "");
if (IsA(coal_em->em_expr, CoalesceExpr)) {
CoalesceExpr* cexpr = (CoalesceExpr*)coal_em->em_expr;
Node* cfirst = NULL;
Node* csecond = NULL;
if (list_length(cexpr->args) != 2)
continue;
cfirst = (Node*)linitial(cexpr->args);
csecond = (Node*)lsecond(cexpr->args);
if (equal(leftvar, cfirst) && equal(rightvar, csecond)) {
match = true;
break;
}
}
}
if (!match)
continue;
* 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 = NULL;
if (!cur_em->em_is_const)
continue;
eq_op = select_equality_operator(cur_ec, left_type, cur_em->em_datatype);
if (OidIsValid(eq_op)) {
newrinfo = build_implied_join_equality(eq_op,
cur_ec->ec_collation,
leftvar,
cur_em->em_expr,
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(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_ptr(cur_ec->ec_members, coal_em);
return true;
}
* Otherwise, fall out of the search loop, since we know the COALESCE
* appears in at most one EC (XXX might stop being true if we allow
* stripping of coercions above?)
*/
break;
}
return false;
}
* 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 = NULL;
foreach (lc1, root->eq_classes) {
EquivalenceClass* ec = (EquivalenceClass*)lfirst(lc1);
bool item1member = false;
bool item2member = false;
ListCell* lc2 = NULL;
if (ec->ec_has_volatile)
continue;
foreach (lc2, ec->ec_members) {
EquivalenceMember* em = (EquivalenceMember*)lfirst(lc2);
if (em->em_is_child)
continue;
if (equal(item1, em->em_expr))
item1member = true;
else if (equal(item2, em->em_expr))
item2member = true;
if (item1member && item2member)
return true;
}
}
return false;
}
* add_child_rel_equivalences
* Search for EC members that reference the parent_rel, and
* add transformed members referencing the child_rel.
*
* Note that this function won't be called at all unless we have at least some
* reason to believe that the EC members it generates will be useful.
*
* parent_rel and child_rel could be derived from appinfo, but since the
* caller has already computed them, we might as well just pass them in.
*/
void add_child_rel_equivalences(
PlannerInfo* root, AppendRelInfo* appinfo, RelOptInfo* parent_rel, RelOptInfo* child_rel)
{
ListCell* lc1 = NULL;
Relids top_parent_relids = child_rel->top_parent_relids ? child_rel->top_parent_relids: parent_rel->relids;
foreach (lc1, root->eq_classes) {
EquivalenceClass* cur_ec = (EquivalenceClass*)lfirst(lc1);
ListCell* lc2 = NULL;
* 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;
if (!bms_is_subset(top_parent_relids, cur_ec->ec_relids))
continue;
foreach (lc2, cur_ec->ec_members) {
EquivalenceMember* cur_em = (EquivalenceMember*)lfirst(lc2);
if (cur_em->em_is_const || cur_em->em_is_child)
continue;
if (bms_overlap(cur_em->em_relids, top_parent_relids)) {
Expr* child_expr = NULL;
Relids new_relids;
Relids new_nullable_relids;
if (parent_rel->reloptkind != RELOPT_OTHER_MEMBER_REL) {
child_expr = (Expr*)adjust_appendrel_attrs(root, (Node*)cur_em->em_expr, appinfo);
} else {
child_expr = (Expr *)adjust_appendrel_attrs_multilevel(root, (Node *)cur_em->em_expr,
child_rel->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_rel->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_rel->relids);
}
(void)add_eq_member(cur_ec, child_expr, new_relids, new_nullable_relids, true, cur_em->em_datatype);
}
}
}
}
* mutate_eclass_expressions
* Apply an expression tree mutator to all expressions stored in
* equivalence classes (but ignore child exprs unless include_child_exprs).
*
* This is a bit of a hack ... it's currently needed only by planagg.c,
* which needs to do a global search-and-replace of MIN/MAX Aggrefs
* after eclasses are already set up. Without changing the eclasses too,
* subsequent matching of ORDER BY and DISTINCT clauses would fail.
*
* Note that we assume the mutation won't affect relation membership or any
* other properties we keep track of (which is a bit bogus, but by the time
* planagg.c runs, it no longer matters). Also we must be called in the
* main planner memory context.
*/
void mutate_eclass_expressions(PlannerInfo* root, Node* (*mutator)(), void* context, bool include_child_exprs)
{
ListCell* lc1 = NULL;
Node* (*p2mutator)(Node*, void*) = (Node* (*)(Node*, void*)) mutator;
foreach (lc1, root->eq_classes) {
EquivalenceClass* cur_ec = (EquivalenceClass*)lfirst(lc1);
ListCell* lc2 = NULL;
foreach (lc2, cur_ec->ec_members) {
EquivalenceMember* cur_em = (EquivalenceMember*)lfirst(lc2);
if (cur_em->em_is_child && !include_child_exprs)
continue;
cur_em->em_expr = (Expr*)p2mutator((Node*)cur_em->em_expr, context);
}
}
}
* generate_implied_equalities_for_indexcol
* Create EC-derived joinclauses usable with a specific index column.
*
* We assume that any given index column could appear in only one EC.
* (This should be true in all but the most pathological cases, and if it
* isn't, we stop on the first match anyway.) Therefore, what we return
* is a redundant list of clauses equating the index column to each of
* the other-relation values it is known to be equal to. Any one of
* these clauses can be used to create a parameterized indexscan, and there
* is no value in using more than one. (But it *is* worthwhile to create
* a separate parameterized path for each one, since that leads to different
* join orders.)
*/
List* generate_implied_equalities_for_indexcol(PlannerInfo* root,
IndexOptInfo* index, int indexcol, Relids prohibited_rels)
{
List* result = NIL;
RelOptInfo* rel = index->rel;
bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
Index parent_relid;
ListCell* lc1 = NULL;
if (is_child_rel)
parent_relid = find_childrel_appendrelinfo(root, rel)->parent_relid;
else
parent_relid = 0;
foreach (lc1, root->eq_classes) {
EquivalenceClass* cur_ec = (EquivalenceClass*)lfirst(lc1);
EquivalenceMember* cur_em = NULL;
ListCell* lc2 = NULL;
* Won't generate joinclauses if const or single-member (the latter
* test covers the volatile case too)
*/
if (cur_ec->ec_has_const || list_length(cur_ec->ec_members) <= 1)
continue;
* No point in searching if rel not mentioned in eclass (but we can't
* tell that for a child rel).
*/
if (!is_child_rel && !bms_is_subset(rel->relids, cur_ec->ec_relids))
continue;
* Scan members, looking for a match to the indexable column. Note
* that child EC members are considered, but only when they belong to
* the target relation. (Unlike regular members, the same expression
* could be a child member of more than one EC. Therefore, it's
* potentially order-dependent which EC a child relation's index
* column gets matched to. This is annoying but it only happens in
* corner cases, so for now we live with just reporting the first
* match. See also get_eclass_for_sort_expr.)
*/
cur_em = NULL;
foreach (lc2, cur_ec->ec_members) {
cur_em = (EquivalenceMember*)lfirst(lc2);
if (bms_equal(cur_em->em_relids, rel->relids) &&
eclass_member_matches_indexcol(cur_ec, cur_em, index, indexcol))
break;
cur_em = NULL;
}
if (cur_em == NULL)
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 = NULL;
if (other_em->em_is_child)
continue;
if (other_em == cur_em || bms_overlap(other_em->em_relids, rel->relids))
continue;
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.
*/
if (is_child_rel && bms_is_member(parent_relid, other_em->em_relids))
continue;
eq_op = select_equality_operator(cur_ec, cur_em->em_datatype, other_em->em_datatype);
if (!OidIsValid(eq_op))
continue;
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 != NULL)
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)
{
ListCell* lc1 = NULL;
foreach (lc1, root->eq_classes) {
EquivalenceClass* ec = (EquivalenceClass*)lfirst(lc1);
* Won't generate joinclauses if single-member (this test covers the
* volatile case too)
*/
if (list_length(ec->ec_members) <= 1)
continue;
* We do not need to examine the individual members of the EC, because
* all that we care about is whether each rel overlaps the relids of
* at least one member, and a test on ec_relids is sufficient to prove
* that. (As with have_relevant_joinclause(), it is not necessary
* that the EC be able to form a joinclause relating exactly the two
* given rels, only that it be able to form a joinclause mentioning
* both, and this will surely be true if both of them overlap
* ec_relids.)
*
* Note we don't test ec_broken; if we did, we'd need a separate code
* path to look through ec_sources. Checking the membership anyway is
* OK as a possibly-overoptimistic heuristic.
*
* We don't test ec_has_const either, even though a const eclass won't
* generate real join clauses. This is because if we had "WHERE a.x =
* b.y and a.x = 42", it is worth considering a join between a and b,
* since the join result is likely to be small even though it'll end
* up being an unqualified nestloop.
*/
if (bms_overlap(rel1->relids, ec->ec_relids) && bms_overlap(rel2->relids, ec->ec_relids))
return true;
}
return false;
}
* has_relevant_eclass_joinclause
* Detect whether there is an EquivalenceClass that could produce
* a joinclause involving the given relation and anything else.
*
* This is the same as have_relevant_eclass_joinclause with the other rel
* implicitly defined as "everything else in the query".
*/
bool has_relevant_eclass_joinclause(PlannerInfo* root, RelOptInfo* rel1)
{
ListCell* lc1 = NULL;
foreach (lc1, root->eq_classes) {
EquivalenceClass* ec = (EquivalenceClass*)lfirst(lc1);
* Won't generate joinclauses if single-member (this test covers the
* volatile case too)
*/
if (list_length(ec->ec_members) <= 1)
continue;
* Per the comment in have_relevant_eclass_joinclause, it's sufficient
* to find an EC that mentions both this rel and some other rel.
*/
if (bms_overlap(rel1->relids, ec->ec_relids) && !bms_is_subset(ec->ec_relids, rel1->relids))
return true;
}
return false;
}
* eclass_useful_for_merging
* Detect whether the EC could produce any mergejoinable join clauses
* against the specified relation.
*
* This is just a heuristic test and doesn't have to be exact; it's better
* to say "yes" incorrectly than "no". Hence we don't bother with details
* like whether the lack of a cross-type operator might prevent the clause
* from actually being generated.
*/
bool eclass_useful_for_merging(EquivalenceClass* eclass, RelOptInfo* rel)
{
ListCell* lc = NULL;
AssertEreport(!eclass->ec_merged, MOD_OPT, "");
* 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 (bms_is_subset(eclass->ec_relids, rel->relids))
return false;
foreach (lc, eclass->ec_members) {
EquivalenceMember* cur_em = (EquivalenceMember*)lfirst(lc);
if (cur_em->em_is_child)
continue;
if (!bms_overlap(cur_em->em_relids, rel->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 = NULL;
if (parent_ec == NULL)
return false;
foreach (lc, clauselist) {
RestrictInfo* otherrinfo = (RestrictInfo*)lfirst(lc);
if (otherrinfo->parent_ec == parent_ec)
return true;
}
return false;
}
* @Description: Get include this expr EquivalenceClass.
* @in root - Per-query information for planning/optimization.
* @in expr - Need to find expr.
* @return - If found return this EquivalenceClass else return NULL.
*/
EquivalenceClass* get_expr_eqClass(PlannerInfo* root, Expr* expr)
{
EquivalenceClass* ec = NULL;
ListCell* lc = NULL;
foreach (lc, root->eq_classes) {
ec = (EquivalenceClass*)lfirst(lc);
bool found = find_ec_memeber_for_var(ec, (Node*)expr);
if (found)
return ec;
}
return NULL;
}
* @Description: Delete this expr from EquivalenceMember which appears in group by clause
* and do not appear in collectiveGroupExpr that means it's value will be altered grouping set after.
* @in root: Per-query information for planning/optimization.
* @in tlist: Targetlist.
* @in collectiveGroupExpr: collective group exprs.
*/
void delete_eq_member(PlannerInfo* root, List* tlist, List* collectiveGroupExpr)
{
List* groupClause = root->parse->groupClause;
List* group_expr = get_sortgrouplist_exprs(groupClause, tlist);
ListCell* lc = NULL;
ListCell* pnext = NULL;
for (lc = list_head(root->eq_classes); lc != NULL; lc = pnext) {
EquivalenceClass* ec = (EquivalenceClass*)lfirst(lc);
pnext = lnext(lc);
ListCell* lc2 = NULL;
ListCell* pnext2 = NULL;
for (lc2 = list_head(ec->ec_members); lc2 != NULL; lc2 = pnext2) {
EquivalenceMember* em = (EquivalenceMember*)lfirst(lc2);
pnext2 = lnext(lc2);
if (list_member(group_expr, em->em_expr) && !list_member(collectiveGroupExpr, em->em_expr)) {
ec->ec_members = list_delete_ptr(ec->ec_members, em);
if (0 == list_length(ec->ec_members)) {
root->eq_classes = list_delete_ptr(root->eq_classes, ec);
}
}
}
}
list_free_ext(group_expr);
}