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/*-------------------------------------------------------------------------
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* Var node manipulation routines
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* Note: for most purposes, PlaceHolderVar is considered a Var too,
7
* even if its contained expression is variable-free. Also, CurrentOfExpr
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* is treated as a Var for purposes of determining whether an expression
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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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#include "access/sysattr.h"
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#include "nodes/nodeFuncs.h"
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#include "optimizer/prep.h"
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#include "optimizer/var.h"
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#include "parser/parsetree.h"
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#include "rewrite/rewriteManip.h"
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} pull_varnos_context;
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} locate_var_of_level_context;
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} locate_var_of_relation_context;
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} find_minimum_var_level_context;
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bool includePlaceHolderVars;
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} pull_var_clause_context;
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} flatten_join_alias_vars_context;
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static bool pull_varnos_walker(Node *node,
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pull_varnos_context *context);
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static bool pull_varattnos_walker(Node *node, Bitmapset **varattnos);
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static bool contain_var_clause_walker(Node *node, void *context);
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static bool contain_vars_of_level_walker(Node *node, int *sublevels_up);
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static bool locate_var_of_level_walker(Node *node,
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locate_var_of_level_context *context);
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static bool locate_var_of_relation_walker(Node *node,
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locate_var_of_relation_context *context);
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static bool find_minimum_var_level_walker(Node *node,
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find_minimum_var_level_context *context);
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static bool pull_var_clause_walker(Node *node,
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pull_var_clause_context *context);
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static Node *flatten_join_alias_vars_mutator(Node *node,
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flatten_join_alias_vars_context *context);
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static Relids alias_relid_set(PlannerInfo *root, Relids relids);
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* Create a set of all the distinct varnos present in a parsetree.
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* Only varnos that reference level-zero rtable entries are considered.
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* NOTE: this is used on not-yet-planned expressions. It may therefore find
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* bare SubLinks, and if so it needs to recurse into them to look for uplevel
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* references to the desired rtable level! But when we find a completed
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* SubPlan, we only need to look at the parameters passed to the subplan.
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pull_varnos(Node *node)
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pull_varnos_context context;
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context.varnos = NULL;
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context.sublevels_up = 0;
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* Must be prepared to start with a Query or a bare expression tree; if
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* it's a Query, we don't want to increment sublevels_up.
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query_or_expression_tree_walker(node,
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return context.varnos;
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pull_varnos_walker(Node *node, pull_varnos_context *context)
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Var *var = (Var *) node;
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if (var->varlevelsup == context->sublevels_up)
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context->varnos = bms_add_member(context->varnos, var->varno);
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if (IsA(node, CurrentOfExpr))
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CurrentOfExpr *cexpr = (CurrentOfExpr *) node;
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if (context->sublevels_up == 0)
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context->varnos = bms_add_member(context->varnos, cexpr->cvarno);
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if (IsA(node, PlaceHolderVar))
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* Normally, we can just take the varnos in the contained expression.
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* But if it is variable-free, use the PHV's syntactic relids.
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PlaceHolderVar *phv = (PlaceHolderVar *) node;
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pull_varnos_context subcontext;
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subcontext.varnos = NULL;
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subcontext.sublevels_up = context->sublevels_up;
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(void) pull_varnos_walker((Node *) phv->phexpr, &subcontext);
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if (bms_is_empty(subcontext.varnos) &&
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phv->phlevelsup == context->sublevels_up)
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context->varnos = bms_add_members(context->varnos, phv->phrels);
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context->varnos = bms_join(context->varnos, subcontext.varnos);
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if (IsA(node, Query))
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/* Recurse into RTE subquery or not-yet-planned sublink subquery */
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context->sublevels_up++;
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result = query_tree_walker((Query *) node, pull_varnos_walker,
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(void *) context, 0);
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context->sublevels_up--;
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return expression_tree_walker(node, pull_varnos_walker,
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* Find all the distinct attribute numbers present in an expression tree,
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* and add them to the initial contents of *varattnos.
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* Only Vars that reference RTE 1 of rtable level zero are considered.
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* Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
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* we can include system attributes (e.g., OID) in the bitmap representation.
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* Currently, this does not support subqueries nor expressions containing
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* references to multiple tables; not needed since it's only applied to
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* index expressions and predicates.
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pull_varattnos(Node *node, Bitmapset **varattnos)
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(void) pull_varattnos_walker(node, varattnos);
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pull_varattnos_walker(Node *node, Bitmapset **varattnos)
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Var *var = (Var *) node;
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Assert(var->varno == 1);
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*varattnos = bms_add_member(*varattnos,
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var->varattno - FirstLowInvalidHeapAttributeNumber);
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/* Should not find a subquery or subplan */
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Assert(!IsA(node, Query));
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Assert(!IsA(node, SubPlan));
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return expression_tree_walker(node, pull_varattnos_walker,
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* Recursively scan a clause to discover whether it contains any Var nodes
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* (of the current query level).
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* Returns true if any varnode found.
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* Does not examine subqueries, therefore must only be used after reduction
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* of sublinks to subplans!
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contain_var_clause(Node *node)
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return contain_var_clause_walker(node, NULL);
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contain_var_clause_walker(Node *node, void *context)
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if (((Var *) node)->varlevelsup == 0)
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return true; /* abort the tree traversal and return true */
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if (IsA(node, CurrentOfExpr))
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if (IsA(node, PlaceHolderVar))
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if (((PlaceHolderVar *) node)->phlevelsup == 0)
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return true; /* abort the tree traversal and return true */
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/* else fall through to check the contained expr */
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return expression_tree_walker(node, contain_var_clause_walker, context);
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* contain_vars_of_level
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* Recursively scan a clause to discover whether it contains any Var nodes
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* of the specified query level.
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* Returns true if any such Var found.
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* Will recurse into sublinks. Also, may be invoked directly on a Query.
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contain_vars_of_level(Node *node, int levelsup)
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int sublevels_up = levelsup;
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return query_or_expression_tree_walker(node,
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contain_vars_of_level_walker,
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(void *) &sublevels_up,
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contain_vars_of_level_walker(Node *node, int *sublevels_up)
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if (((Var *) node)->varlevelsup == *sublevels_up)
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return true; /* abort tree traversal and return true */
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if (IsA(node, CurrentOfExpr))
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if (*sublevels_up == 0)
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if (IsA(node, PlaceHolderVar))
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if (((PlaceHolderVar *) node)->phlevelsup == *sublevels_up)
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return true; /* abort the tree traversal and return true */
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/* else fall through to check the contained expr */
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if (IsA(node, Query))
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/* Recurse into subselects */
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result = query_tree_walker((Query *) node,
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contain_vars_of_level_walker,
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(void *) sublevels_up,
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return expression_tree_walker(node,
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contain_vars_of_level_walker,
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(void *) sublevels_up);
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* locate_var_of_level
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* Find the parse location of any Var of the specified query level.
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* Returns -1 if no such Var is in the querytree, or if they all have
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* unknown parse location. (The former case is probably caller error,
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* but we don't bother to distinguish it from the latter case.)
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* Will recurse into sublinks. Also, may be invoked directly on a Query.
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* Note: it might seem appropriate to merge this functionality into
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* contain_vars_of_level, but that would complicate that function's API.
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* Currently, the only uses of this function are for error reporting,
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* and so shaving cycles probably isn't very important.
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locate_var_of_level(Node *node, int levelsup)
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locate_var_of_level_context context;
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context.var_location = -1; /* in case we find nothing */
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context.sublevels_up = levelsup;
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(void) query_or_expression_tree_walker(node,
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locate_var_of_level_walker,
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return context.var_location;
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locate_var_of_level_walker(Node *node,
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locate_var_of_level_context *context)
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Var *var = (Var *) node;
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if (var->varlevelsup == context->sublevels_up &&
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context->var_location = var->location;
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return true; /* abort tree traversal and return true */
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if (IsA(node, CurrentOfExpr))
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/* since CurrentOfExpr doesn't carry location, nothing we can do */
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/* No extra code needed for PlaceHolderVar; just look in contained expr */
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if (IsA(node, Query))
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/* Recurse into subselects */
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context->sublevels_up++;
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result = query_tree_walker((Query *) node,
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locate_var_of_level_walker,
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context->sublevels_up--;
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return expression_tree_walker(node,
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locate_var_of_level_walker,
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* locate_var_of_relation
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* Find the parse location of any Var of the specified relation.
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* Returns -1 if no such Var is in the querytree, or if they all have
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* unknown parse location.
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* Will recurse into sublinks. Also, may be invoked directly on a Query.
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locate_var_of_relation(Node *node, int relid, int levelsup)
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locate_var_of_relation_context context;
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context.var_location = -1; /* in case we find nothing */
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context.relid = relid;
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context.sublevels_up = levelsup;
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(void) query_or_expression_tree_walker(node,
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locate_var_of_relation_walker,
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return context.var_location;
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locate_var_of_relation_walker(Node *node,
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locate_var_of_relation_context *context)
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Var *var = (Var *) node;
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if (var->varno == context->relid &&
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var->varlevelsup == context->sublevels_up &&
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context->var_location = var->location;
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return true; /* abort tree traversal and return true */
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if (IsA(node, CurrentOfExpr))
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/* since CurrentOfExpr doesn't carry location, nothing we can do */
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/* No extra code needed for PlaceHolderVar; just look in contained expr */
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if (IsA(node, Query))
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/* Recurse into subselects */
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context->sublevels_up++;
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result = query_tree_walker((Query *) node,
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locate_var_of_relation_walker,
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context->sublevels_up--;
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return expression_tree_walker(node,
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locate_var_of_relation_walker,
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* find_minimum_var_level
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* Recursively scan a clause to find the lowest variable level it
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* contains --- for example, zero is returned if there are any local
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* variables, one if there are no local variables but there are
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* one-level-up outer references, etc. Subqueries are scanned to see
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* if they possess relevant outer references. (But any local variables
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* within subqueries are not relevant.)
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* -1 is returned if the clause has no variables at all.
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* Will recurse into sublinks. Also, may be invoked directly on a Query.
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find_minimum_var_level(Node *node)
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find_minimum_var_level_context context;
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context.min_varlevel = -1; /* signifies nothing found yet */
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context.sublevels_up = 0;
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(void) query_or_expression_tree_walker(node,
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find_minimum_var_level_walker,
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return context.min_varlevel;
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find_minimum_var_level_walker(Node *node,
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find_minimum_var_level_context *context)
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int varlevelsup = ((Var *) node)->varlevelsup;
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/* convert levelsup to frame of reference of original query */
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varlevelsup -= context->sublevels_up;
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/* ignore local vars of subqueries */
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if (varlevelsup >= 0)
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if (context->min_varlevel < 0 ||
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context->min_varlevel > varlevelsup)
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context->min_varlevel = varlevelsup;
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* As soon as we find a local variable, we can abort the tree
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* traversal, since min_varlevel is then certainly 0.
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if (varlevelsup == 0)
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if (IsA(node, CurrentOfExpr))
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/* convert levelsup to frame of reference of original query */
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varlevelsup -= context->sublevels_up;
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/* ignore local vars of subqueries */
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if (varlevelsup >= 0)
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if (context->min_varlevel < 0 ||
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context->min_varlevel > varlevelsup)
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context->min_varlevel = varlevelsup;
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* As soon as we find a local variable, we can abort the tree
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* traversal, since min_varlevel is then certainly 0.
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if (varlevelsup == 0)
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* An Aggref must be treated like a Var of its level. Normally we'd get
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* the same result from looking at the Vars in the aggregate's argument,
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* but this fails in the case of a Var-less aggregate call (COUNT(*)).
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if (IsA(node, Aggref))
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int agglevelsup = ((Aggref *) node)->agglevelsup;
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/* convert levelsup to frame of reference of original query */
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agglevelsup -= context->sublevels_up;
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/* ignore local aggs of subqueries */
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if (agglevelsup >= 0)
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if (context->min_varlevel < 0 ||
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context->min_varlevel > agglevelsup)
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context->min_varlevel = agglevelsup;
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* As soon as we find a local aggregate, we can abort the tree
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* traversal, since min_varlevel is then certainly 0.
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if (agglevelsup == 0)
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/* Likewise, make sure PlaceHolderVar is treated correctly */
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if (IsA(node, PlaceHolderVar))
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int phlevelsup = ((PlaceHolderVar *) node)->phlevelsup;
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/* convert levelsup to frame of reference of original query */
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phlevelsup -= context->sublevels_up;
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/* ignore local vars of subqueries */
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if (context->min_varlevel < 0 ||
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context->min_varlevel > phlevelsup)
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context->min_varlevel = phlevelsup;
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* As soon as we find a local variable, we can abort the tree
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* traversal, since min_varlevel is then certainly 0.
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if (IsA(node, Query))
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/* Recurse into subselects */
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context->sublevels_up++;
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result = query_tree_walker((Query *) node,
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find_minimum_var_level_walker,
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context->sublevels_up--;
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return expression_tree_walker(node,
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find_minimum_var_level_walker,
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* Recursively pulls all Var nodes from an expression clause.
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* PlaceHolderVars are included too, if includePlaceHolderVars is true.
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* If it isn't true, an error is thrown if any are found.
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* Note that Vars within a PHV's expression are *not* included.
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* CurrentOfExpr nodes are *not* included.
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* Upper-level vars (with varlevelsup > 0) are not included.
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* (These probably represent errors too, but we don't complain.)
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* Returns list of nodes found. Note the nodes themselves are not
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* copied, only referenced.
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* Does not examine subqueries, therefore must only be used after reduction
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* of sublinks to subplans!
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pull_var_clause(Node *node, bool includePlaceHolderVars)
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pull_var_clause_context context;
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context.varlist = NIL;
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context.includePlaceHolderVars = includePlaceHolderVars;
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pull_var_clause_walker(node, &context);
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return context.varlist;
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pull_var_clause_walker(Node *node, pull_var_clause_context *context)
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if (((Var *) node)->varlevelsup == 0)
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context->varlist = lappend(context->varlist, node);
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if (IsA(node, PlaceHolderVar))
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if (!context->includePlaceHolderVars)
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elog(ERROR, "PlaceHolderVar found where not expected");
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if (((PlaceHolderVar *) node)->phlevelsup == 0)
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context->varlist = lappend(context->varlist, node);
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/* we do NOT descend into the contained expression */
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return expression_tree_walker(node, pull_var_clause_walker,
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* flatten_join_alias_vars
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* Replace Vars that reference JOIN outputs with references to the original
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* relation variables instead. This allows quals involving such vars to be
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* pushed down. Whole-row Vars that reference JOIN relations are expanded
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* into RowExpr constructs that name the individual output Vars. This
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* is necessary since we will not scan the JOIN as a base relation, which
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* is the only way that the executor can directly handle whole-row Vars.
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* This also adjusts relid sets found in some expression node types to
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* substitute the contained base rels for any join relid.
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* NOTE: this is used on not-yet-planned expressions. We do not expect it
682
* to be applied directly to a Query node.
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flatten_join_alias_vars(PlannerInfo *root, Node *node)
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flatten_join_alias_vars_context context;
690
context.sublevels_up = 0;
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return flatten_join_alias_vars_mutator(node, &context);
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flatten_join_alias_vars_mutator(Node *node,
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flatten_join_alias_vars_context *context)
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Var *var = (Var *) node;
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/* No change unless Var belongs to a JOIN of the target level */
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if (var->varlevelsup != context->sublevels_up)
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return node; /* no need to copy, really */
710
rte = rt_fetch(var->varno, context->root->parse->rtable);
711
if (rte->rtekind != RTE_JOIN)
713
if (var->varattno == InvalidAttrNumber)
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/* Must expand whole-row reference */
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foreach(l, rte->joinaliasvars)
724
newvar = (Node *) lfirst(l);
726
/* Ignore dropped columns */
727
if (IsA(newvar, Const))
731
* If we are expanding an alias carried down from an upper
732
* query, must adjust its varlevelsup fields.
734
if (context->sublevels_up != 0)
736
newvar = copyObject(newvar);
737
IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
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/* Recurse in case join input is itself a join */
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newvar = flatten_join_alias_vars_mutator(newvar, context);
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fields = lappend(fields, newvar);
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rowexpr = makeNode(RowExpr);
744
rowexpr->args = fields;
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rowexpr->row_typeid = var->vartype;
746
rowexpr->row_format = COERCE_IMPLICIT_CAST;
747
rowexpr->colnames = NIL;
748
rowexpr->location = -1;
750
return (Node *) rowexpr;
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/* Expand join alias reference */
754
Assert(var->varattno > 0);
755
newvar = (Node *) list_nth(rte->joinaliasvars, var->varattno - 1);
758
* If we are expanding an alias carried down from an upper query, must
759
* adjust its varlevelsup fields.
761
if (context->sublevels_up != 0)
763
newvar = copyObject(newvar);
764
IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
766
/* Recurse in case join input is itself a join */
767
return flatten_join_alias_vars_mutator(newvar, context);
769
if (IsA(node, PlaceHolderVar))
771
/* Copy the PlaceHolderVar node with correct mutation of subnodes */
774
phv = (PlaceHolderVar *) expression_tree_mutator(node,
775
flatten_join_alias_vars_mutator,
777
/* now fix PlaceHolderVar's relid sets */
778
if (phv->phlevelsup == context->sublevels_up)
780
phv->phrels = alias_relid_set(context->root,
786
if (IsA(node, Query))
788
/* Recurse into RTE subquery or not-yet-planned sublink subquery */
791
context->sublevels_up++;
792
newnode = query_tree_mutator((Query *) node,
793
flatten_join_alias_vars_mutator,
795
QTW_IGNORE_JOINALIASES);
796
context->sublevels_up--;
797
return (Node *) newnode;
799
/* Already-planned tree not supported */
800
Assert(!IsA(node, SubPlan));
801
/* Shouldn't need to handle these planner auxiliary nodes here */
802
Assert(!IsA(node, SpecialJoinInfo));
803
Assert(!IsA(node, PlaceHolderInfo));
805
return expression_tree_mutator(node, flatten_join_alias_vars_mutator,
810
* alias_relid_set: in a set of RT indexes, replace joins by their
811
* underlying base relids
814
alias_relid_set(PlannerInfo *root, Relids relids)
816
Relids result = NULL;
820
tmprelids = bms_copy(relids);
821
while ((rtindex = bms_first_member(tmprelids)) >= 0)
823
RangeTblEntry *rte = rt_fetch(rtindex, root->parse->rtable);
825
if (rte->rtekind == RTE_JOIN)
826
result = bms_join(result, get_relids_for_join(root, rtindex));
828
result = bms_add_member(result, rtindex);