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/*-------------------------------------------------------------------------
*
* ordering.c
* Routines to manipulate and compare merge and path orderings
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/Attic/ordering.c,v 1.16 1999/05/25 16:09:57 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include <sys/types.h>
#include "postgres.h"
#include "optimizer/internal.h"
#include "optimizer/ordering.h"
static bool sortops_order_match(Oid *ordering1, Oid *ordering2,
int *better_sort);
/*
* equal_path_ordering
* Returns t iff two path orderings are equal.
*
*/
bool
pathorder_match(PathOrder *path_ordering1,
PathOrder *path_ordering2,
int *better_sort)
{
*better_sort = 0;
if (path_ordering1 == path_ordering2)
return true;
if (!path_ordering2)
{
*better_sort = 1;
return true;
}
if (!path_ordering1)
{
*better_sort = 2;
return true;
}
if (path_ordering1->ordtype == MERGE_ORDER &&
path_ordering2->ordtype == MERGE_ORDER)
return equal(path_ordering1->ord.merge, path_ordering2->ord.merge);
else if (path_ordering1->ordtype == SORTOP_ORDER &&
path_ordering2->ordtype == SORTOP_ORDER)
{
return sortops_order_match(path_ordering1->ord.sortop,
path_ordering2->ord.sortop,
better_sort);
}
else if (path_ordering1->ordtype == MERGE_ORDER &&
path_ordering2->ordtype == SORTOP_ORDER)
{
if (!path_ordering2->ord.sortop)
{
*better_sort = 1;
return true;
}
return path_ordering1->ord.merge->left_operator == path_ordering2->ord.sortop[0];
}
else
{
if (!path_ordering1->ord.sortop)
{
*better_sort = 2;
return true;
}
return path_ordering1->ord.sortop[0] == path_ordering2->ord.merge->left_operator;
}
}
/*
* equal_path_merge_ordering
* Returns t iff a path ordering is usable for ordering a merge join.
*
* XXX Presently, this means that the first sortop of the path matches
* either of the merge sortops. Is there a "right" and "wrong"
* sortop to match?
*
*/
bool
equal_path_merge_ordering(Oid *path_ordering,
MergeOrder *merge_ordering)
{
if (path_ordering == NULL || merge_ordering == NULL)
return false;
if (path_ordering[0] == merge_ordering->left_operator ||
path_ordering[0] == merge_ordering->right_operator)
return true;
else
return false;
}
/*
* equal_merge_ordering
* Returns t iff two merge orderings are equal.
*
*/
bool
equal_merge_ordering(MergeOrder *merge_ordering1,
MergeOrder *merge_ordering2)
{
return equal(merge_ordering1, merge_ordering2);
}
/*
* sortops
*
*/
/*
* equal_sort_ops_order -
* Returns true iff the sort operators are in the same order.
*/
static bool
sortops_order_match(Oid *ordering1, Oid *ordering2, int *better_sort)
{
int i = 0;
*better_sort = 0;
if (ordering1 == ordering2)
return true;
if (!ordering2)
{
*better_sort = 1;
return true;
}
if (!ordering1)
{
*better_sort = 2;
return true;
}
while (ordering1[i] != 0 && ordering2[i] != 0)
{
if (ordering1[i] != ordering2[i])
break;
i++;
}
if (ordering1[i] != 0 && ordering2[i] == 0)
{
*better_sort = 1;
return true;
}
if (ordering1[i] == 0 && ordering2[i] != 0)
{
*better_sort = 2;
return true;
}
return ordering1[i] == 0 && ordering2[i] == 0;
}
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