Fix set_append_rel_pathlist() to deal intelligently with cases where
substituting a child rel's output expressions into the appendrel's restriction clauses yields a pseudoconstant restriction. We might be able to skip scanning that child rel entirely (if we get constant FALSE), or generate a one-time filter. 8.3 more or less accidentally generated plans that weren't completely stupid in these cases, but that was only because an extra recursive level of subquery_planner() always occurred and allowed const-simplification to happen. 8.4's ability to pull up appendrel members with non-Var outputs exposes the fact that we need to work harder here. Per gripe from Sergey Burladyan.
This commit is contained in:
Tom Lane
parent
d0f6725090
commit
c75235949a
@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.183 2009/06/11 14:48:58 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.183.2.1 2009/07/06 18:26:38 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -29,6 +29,7 @@
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#include "optimizer/plancat.h"
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#include "optimizer/planner.h"
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#include "optimizer/prep.h"
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#include "optimizer/restrictinfo.h"
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#include "optimizer/var.h"
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#include "parser/parse_clause.h"
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#include "parser/parsetree.h"
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@ -318,6 +319,8 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
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int childRTindex;
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RangeTblEntry *childRTE;
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RelOptInfo *childrel;
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List *childquals;
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Node *childqual;
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Path *childpath;
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ListCell *parentvars;
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ListCell *childvars;
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@ -342,10 +345,34 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
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* baserestrictinfo quals are needed before we can check for
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* constraint exclusion; so do that first and then check to see if we
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* can disregard this child.
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*
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* As of 8.4, the child rel's targetlist might contain non-Var
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* expressions, which means that substitution into the quals
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* could produce opportunities for const-simplification, and perhaps
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* even pseudoconstant quals. To deal with this, we strip the
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* RestrictInfo nodes, do the substitution, do const-simplification,
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* and then reconstitute the RestrictInfo layer.
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*/
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childrel->baserestrictinfo = (List *)
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adjust_appendrel_attrs((Node *) rel->baserestrictinfo,
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appinfo);
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childquals = get_all_actual_clauses(rel->baserestrictinfo);
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childquals = (List *) adjust_appendrel_attrs((Node *) childquals,
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appinfo);
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childqual = eval_const_expressions(root, (Node *)
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make_ands_explicit(childquals));
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if (childqual && IsA(childqual, Const) &&
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(((Const *) childqual)->constisnull ||
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!DatumGetBool(((Const *) childqual)->constvalue)))
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{
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/*
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* Restriction reduces to constant FALSE or constant NULL after
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* substitution, so this child need not be scanned.
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*/
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set_dummy_rel_pathlist(childrel);
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continue;
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}
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childquals = make_ands_implicit((Expr *) childqual);
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childquals = make_restrictinfos_from_actual_clauses(root,
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childquals);
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childrel->baserestrictinfo = childquals;
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if (relation_excluded_by_constraints(root, childrel, childRTE))
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{
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@ -22,7 +22,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.171 2009/06/11 14:48:59 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.171.2.1 2009/07/06 18:26:39 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1636,57 +1636,7 @@ adjust_appendrel_attrs_mutator(Node *node, AppendRelInfo *context)
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Assert(!IsA(node, SpecialJoinInfo));
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Assert(!IsA(node, AppendRelInfo));
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Assert(!IsA(node, PlaceHolderInfo));
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/*
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* We have to process RestrictInfo nodes specially.
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*/
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if (IsA(node, RestrictInfo))
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{
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RestrictInfo *oldinfo = (RestrictInfo *) node;
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RestrictInfo *newinfo = makeNode(RestrictInfo);
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/* Copy all flat-copiable fields */
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memcpy(newinfo, oldinfo, sizeof(RestrictInfo));
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/* Recursively fix the clause itself */
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newinfo->clause = (Expr *)
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adjust_appendrel_attrs_mutator((Node *) oldinfo->clause, context);
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/* and the modified version, if an OR clause */
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newinfo->orclause = (Expr *)
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adjust_appendrel_attrs_mutator((Node *) oldinfo->orclause, context);
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/* adjust relid sets too */
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newinfo->clause_relids = adjust_relid_set(oldinfo->clause_relids,
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context->parent_relid,
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context->child_relid);
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newinfo->required_relids = adjust_relid_set(oldinfo->required_relids,
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context->parent_relid,
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context->child_relid);
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newinfo->left_relids = adjust_relid_set(oldinfo->left_relids,
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context->parent_relid,
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context->child_relid);
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newinfo->right_relids = adjust_relid_set(oldinfo->right_relids,
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context->parent_relid,
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context->child_relid);
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/*
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* Reset cached derivative fields, since these might need to have
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* different values when considering the child relation.
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*/
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newinfo->eval_cost.startup = -1;
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newinfo->norm_selec = -1;
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newinfo->outer_selec = -1;
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newinfo->left_ec = NULL;
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newinfo->right_ec = NULL;
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newinfo->left_em = NULL;
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newinfo->right_em = NULL;
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newinfo->scansel_cache = NIL;
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newinfo->left_bucketsize = -1;
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newinfo->right_bucketsize = -1;
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return (Node *) newinfo;
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}
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Assert(!IsA(node, RestrictInfo));
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/*
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* NOTE: we do not need to recurse into sublinks, because they should
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.60 2009/06/11 14:48:59 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/util/restrictinfo.c,v 1.60.2.1 2009/07/06 18:26:39 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -271,6 +271,57 @@ make_restrictinfo_from_bitmapqual(Path *bitmapqual,
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return result;
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}
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/*
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* make_restrictinfos_from_actual_clauses
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*
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* Given a list of implicitly-ANDed restriction clauses, produce a list
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* of RestrictInfo nodes. This is used to reconstitute the RestrictInfo
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* representation after doing transformations of a list of clauses.
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*
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* We assume that the clauses are relation-level restrictions and therefore
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* we don't have to worry about is_pushed_down, outerjoin_delayed, or
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* nullable_relids (these can be assumed true, false, and NULL, respectively).
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* We do take care to recognize pseudoconstant clauses properly.
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*/
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List *
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make_restrictinfos_from_actual_clauses(PlannerInfo *root,
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List *clause_list)
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{
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List *result = NIL;
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ListCell *l;
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foreach(l, clause_list)
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{
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Expr *clause = (Expr *) lfirst(l);
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bool pseudoconstant;
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RestrictInfo *rinfo;
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/*
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* It's pseudoconstant if it contains no Vars and no volatile
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* functions. We probably can't see any sublinks here, so
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* contain_var_clause() would likely be enough, but for safety
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* use contain_vars_of_level() instead.
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*/
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pseudoconstant =
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!contain_vars_of_level((Node *) clause, 0) &&
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!contain_volatile_functions((Node *) clause);
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if (pseudoconstant)
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{
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/* tell createplan.c to check for gating quals */
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root->hasPseudoConstantQuals = true;
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}
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rinfo = make_restrictinfo(clause,
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true,
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false,
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pseudoconstant,
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NULL,
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NULL);
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result = lappend(result, rinfo);
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}
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return result;
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}
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/*
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* make_restrictinfo_internal
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*
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@ -481,6 +532,31 @@ get_actual_clauses(List *restrictinfo_list)
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return result;
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}
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/*
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* get_all_actual_clauses
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*
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* Returns a list containing the bare clauses from 'restrictinfo_list'.
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*
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* This loses the distinction between regular and pseudoconstant clauses,
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* so be careful what you use it for.
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*/
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List *
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get_all_actual_clauses(List *restrictinfo_list)
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{
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List *result = NIL;
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ListCell *l;
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foreach(l, restrictinfo_list)
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{
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RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
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Assert(IsA(rinfo, RestrictInfo));
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result = lappend(result, rinfo->clause);
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}
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return result;
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}
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/*
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* extract_actual_clauses
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*
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/optimizer/restrictinfo.h,v 1.44 2009/05/09 22:51:41 tgl Exp $
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* $PostgreSQL: pgsql/src/include/optimizer/restrictinfo.h,v 1.44.2.1 2009/07/06 18:26:39 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -30,8 +30,11 @@ extern RestrictInfo *make_restrictinfo(Expr *clause,
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extern List *make_restrictinfo_from_bitmapqual(Path *bitmapqual,
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bool is_pushed_down,
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bool include_predicates);
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extern List *make_restrictinfos_from_actual_clauses(PlannerInfo *root,
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List *clause_list);
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extern bool restriction_is_or_clause(RestrictInfo *restrictinfo);
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extern List *get_actual_clauses(List *restrictinfo_list);
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extern List *get_all_actual_clauses(List *restrictinfo_list);
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extern List *extract_actual_clauses(List *restrictinfo_list,
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bool pseudoconstant);
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extern void extract_actual_join_clauses(List *restrictinfo_list,
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