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Fix tuplecmp() to ensure repeatable sort ordering of tuples 

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
View File

@ -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;
}