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/*-------------------------------------------------------------------------
*
* mergeutils.c
* Utilities for finding applicable merge clauses and pathkeys
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/Attic/mergeutils.c,v 1.20 1999/03/01 00:10:32 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/pg_list.h"
#include "nodes/relation.h"
#include "optimizer/internal.h"
#include "optimizer/paths.h"
#include "optimizer/clauses.h"
#include "optimizer/ordering.h"
/*
* group_clauses_by_order
* If a join clause node in 'restrictinfo_list' is mergejoinable, store
* it within a mergeinfo node containing other clause nodes with the same
* mergejoin ordering.
*
* XXX This is completely braindead: there is no reason anymore to segregate
* mergejoin clauses by join operator, since the executor can handle mergejoin
* clause sets with different operators in them. Instead, we ought to be
* building a MergeInfo for each potentially useful ordering of the input
* relations. But right now the optimizer's internal data structures do not
* support that (MergeInfo can only store one MergeOrder for a set of clauses).
* Something to fix next time...
*
* 'restrictinfo_list' is the list of restrictinfo nodes
* 'inner_relid' is the relid of the inner join relation
*
* Returns the new list of mergeinfo nodes.
*
*/
List *
group_clauses_by_order(List *restrictinfo_list,
int inner_relid)
{
List *mergeinfo_list = NIL;
List *xrestrictinfo;
foreach(xrestrictinfo, restrictinfo_list)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(xrestrictinfo);
MergeOrder *merge_ordering = restrictinfo->mergejoinorder;
if (merge_ordering)
{
/*
* Create a new mergeinfo node and add it to 'mergeinfo_list'
* if one does not yet exist for this merge ordering.
*/
PathOrder *pathorder;
MergeInfo *xmergeinfo;
Expr *clause = restrictinfo->clause;
Var *leftop = get_leftop(clause);
Var *rightop = get_rightop(clause);
JoinKey *jmkeys;
pathorder = makeNode(PathOrder);
pathorder->ordtype = MERGE_ORDER;
pathorder->ord.merge = merge_ordering;
xmergeinfo = match_order_mergeinfo(pathorder, mergeinfo_list);
if (inner_relid == leftop->varno)
{
jmkeys = makeNode(JoinKey);
jmkeys->outer = rightop;
jmkeys->inner = leftop;
}
else
{
jmkeys = makeNode(JoinKey);
jmkeys->outer = leftop;
jmkeys->inner = rightop;
}
if (xmergeinfo == NULL)
{
xmergeinfo = makeNode(MergeInfo);
xmergeinfo->m_ordering = merge_ordering;
mergeinfo_list = lcons(xmergeinfo,
mergeinfo_list);
}
xmergeinfo->jmethod.clauses = lcons(clause,
xmergeinfo->jmethod.clauses);
xmergeinfo->jmethod.jmkeys = lcons(jmkeys,
xmergeinfo->jmethod.jmkeys);
}
}
return mergeinfo_list;
}
/*
* match_order_mergeinfo
* Searches the list 'mergeinfo_list' for a mergeinfo node whose order
* field equals 'ordering'.
*
* Returns the node if it exists.
*
*/
MergeInfo *
match_order_mergeinfo(PathOrder *ordering, List *mergeinfo_list)
{
MergeOrder *xmergeorder;
List *xmergeinfo = NIL;
foreach(xmergeinfo, mergeinfo_list)
{
MergeInfo *mergeinfo = (MergeInfo *) lfirst(xmergeinfo);
xmergeorder = mergeinfo->m_ordering;
if ((ordering->ordtype == MERGE_ORDER &&
equal_merge_ordering(ordering->ord.merge, xmergeorder)) ||
(ordering->ordtype == SORTOP_ORDER &&
equal_path_merge_ordering(ordering->ord.sortop, xmergeorder)))
{
return mergeinfo;
}
}
return (MergeInfo *) NIL;
}
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