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/*-------------------------------------------------------------------------
*
* joininfo.c--
* JoinInfo node manipulation routines
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/joininfo.c,v 1.14 1999/02/10 21:02:40 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/relation.h"
#include "optimizer/internal.h"
#include "optimizer/joininfo.h"
#include "optimizer/var.h"
#include "optimizer/clauses.h"
/*
* joininfo-member--
* Determines whether a node has already been created for a join
* between a set of join relations and the relation described by
* 'joininfo-list'.
*
* 'join-relids' is a list of relids corresponding to the join relation
* 'joininfo-list' is the list of joininfo nodes against which this is
* checked
*
* Returns the corresponding node in 'joininfo-list' if such a node
* exists.
*
*/
JoinInfo *
joininfo_member(List *join_relids, List *joininfo_list)
{
List *i = NIL;
List *other_rels = NIL;
foreach(i, joininfo_list)
{
other_rels = lfirst(i);
if (same(join_relids, ((JoinInfo *) other_rels)->otherrels))
return (JoinInfo *) other_rels;
}
return (JoinInfo *) NULL;
}
/*
* find-joininfo-node--
* Find the joininfo node within a relation entry corresponding
* to a join between 'this_rel' and the relations in 'join-relids'. A
* new node is created and added to the relation entry's joininfo
* field if the desired one can't be found.
*
* Returns a joininfo node.
*
*/
JoinInfo *
find_joininfo_node(RelOptInfo *this_rel, List *join_relids)
{
JoinInfo *joininfo = joininfo_member(join_relids,
this_rel->joininfo);
if (joininfo == NULL)
{
joininfo = makeNode(JoinInfo);
joininfo->otherrels = join_relids;
joininfo->jinfo_restrictinfo = NIL;
joininfo->mergejoinable = false;
joininfo->hashjoinable = false;
joininfo->inactive = false;
this_rel->joininfo = lcons(joininfo, this_rel->joininfo);
}
return joininfo;
}
/*
* other-join-clause-var--
* Determines whether a var node is contained within a joinclause
* of the form(op var var).
*
* Returns the other var node in the joinclause if it is, nil if not.
*
*/
Var *
other_join_clause_var(Var *var, Expr *clause)
{
Var *retval;
Var *l,
*r;
retval = (Var *) NULL;
if (var != NULL && is_joinable((Node *) clause))
{
l = (Var *) get_leftop(clause);
r = (Var *) get_rightop(clause);
if (var_equal(var, l))
retval = r;
else if (var_equal(var, r))
retval = l;
}
return retval;
}
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