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Fix tuplecmp() to ensure repeatable sort ordering of tuples

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that contain null fields.  Old code would produce erratic sort results
because comparisons of tuples containing nulls could produce inconsistent
answers.
This commit is contained in:
Tom Lane 1999-07-10 18:21:59 +00:00
parent bc5f34c89e
commit cc62dc2032
1 changed files with 32 additions and 24 deletions
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56
src/backend/utils/sort/lselect.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/sort/Attic/lselect.c,v 1.15 1999/02/13 23:20:15 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/sort/Attic/lselect.c,v 1.16 1999/07/10 18:21:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -186,41 +186,49 @@ puttuple(struct leftist ** treep,
int
tuplecmp(HeapTuple ltup, HeapTuple rtup, LeftistContext context)
{
Datum lattr,
rattr;
int nkey = 0;
int nkey;
int result = 0;
bool isnull;
if (ltup == (HeapTuple) NULL)
return 0;
if (rtup == (HeapTuple) NULL)
return 1;
while (nkey < context->nKeys && !result)
for (nkey = 0; nkey < context->nKeys; nkey++)
{
lattr = heap_getattr(ltup,
context->scanKeys[nkey].sk_attno,
context->tupDesc, &isnull);
if (isnull)
return 0;
rattr = heap_getattr(rtup,
context->scanKeys[nkey].sk_attno,
context->tupDesc,
&isnull);
if (isnull)
ScanKey thisKey = & context->scanKeys[nkey];
Datum lattr,
rattr;
bool lisnull,
risnull;
lattr = heap_getattr(ltup, thisKey->sk_attno,
context->tupDesc, &lisnull);
rattr = heap_getattr(rtup, thisKey->sk_attno,
context->tupDesc, &risnull);
if (lisnull)
{
if (risnull)
continue; /* treat two nulls as equal */
return 0; /* else, a null sorts after all else */
}
if (risnull)
return 1;
if (context->scanKeys[nkey].sk_flags & SK_COMMUTE)
if (thisKey->sk_flags & SK_COMMUTE)
{
if (!(result =
(long) (*fmgr_faddr(&context->scanKeys[nkey].sk_func)) (rattr, lattr)))
(long) (*fmgr_faddr(&thisKey->sk_func)) (rattr, lattr)))
result =
-(long) (*fmgr_faddr(&context->scanKeys[nkey].sk_func)) (lattr, rattr);
-(long) (*fmgr_faddr(&thisKey->sk_func)) (lattr, rattr);
}
else if (!(result =
(long) (*fmgr_faddr(&context->scanKeys[nkey].sk_func)) (lattr, rattr)))
result =
-(long) (*fmgr_faddr(&context->scanKeys[nkey].sk_func)) (rattr, lattr);
nkey++;
else
{
if (!(result =
(long) (*fmgr_faddr(&thisKey->sk_func)) (lattr, rattr)))
result =
-(long) (*fmgr_faddr(&thisKey->sk_func)) (rattr, lattr);
}
if (result)
break;
}
return result == 1;
}