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/*-------------------------------------------------------------------------
*
* joininfo.c
* JoinInfo node manipulation routines
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/joininfo.c,v 1.31 2002/06/20 20:29:31 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "optimizer/joininfo.h"
static JoinInfo *joininfo_member(List *join_relids, List *joininfo_list);
/*
* 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.
*
*/
static JoinInfo *
joininfo_member(List *join_relids, List *joininfo_list)
{
List *i;
foreach(i, joininfo_list)
{
JoinInfo *joininfo = (JoinInfo *) lfirst(i);
if (sameseti(join_relids, joininfo->unjoined_relids))
return joininfo;
}
return 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, Relids join_relids)
{
JoinInfo *joininfo = joininfo_member(join_relids,
this_rel->joininfo);
if (joininfo == NULL)
{
joininfo = makeNode(JoinInfo);
joininfo->unjoined_relids = join_relids;
joininfo->jinfo_restrictinfo = NIL;
this_rel->joininfo = lcons(joininfo, this_rel->joininfo);
}
return joininfo;
}
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