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Fixes: 

I found another bug in btree index.  Looking at the code it seems that NULL
keys are never used to build or scan a btree index (see the explain commands
in the example).  However this is not the case when a null key is retrieved
in an outer loop of a join select and used in an index scan of an inner loop.
This bug causes at least three kinds of problems:

1)  the backend crashes when it tries to compare a text string with a null.

2)  it is not possible to find tuples with null keys in a join.

3)  null is considered equal to 0 when the datum is passed by value, see
    the last query.

Submitted by: Massimo Dal Zotto <dz@cs.unitn.it>
This commit is contained in:
Marc G. Fournier 1996-10-30 06:08:10 +00:00
parent 6ada9dfdce
commit 69c7f25bed
4 changed files with 43 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
src/backend/access/common/heapvalid.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/common/Attic/heapvalid.c,v 1.6 1996/10/21 11:49:36 scrappy Exp $
* $Header: /cvsroot/pgsql/src/backend/access/common/Attic/heapvalid.c,v 1.7 1996/10/30 06:07:56 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
@ -71,6 +71,10 @@ heap_keytest(HeapTuple t,
/* XXX eventually should check if SK_ISNULL */
return false;
if (keys->sk_flags & SK_ISNULL) {
return (false);
}
if (keys->sk_flags & SK_COMMUTE)
test = (long) FMGR_PTR2(keys->sk_func, keys->sk_procedure,
keys->sk_argument, atp);

6
src/backend/access/common/indexvalid.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/common/Attic/indexvalid.c,v 1.6 1996/10/21 11:49:38 scrappy Exp $
* $Header: /cvsroot/pgsql/src/backend/access/common/Attic/indexvalid.c,v 1.7 1996/10/30 06:07:55 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
@ -68,6 +68,10 @@ index_keytest(IndexTuple tuple,
return (false);
}
if (key[0].sk_flags & SK_ISNULL) {
return (false);
}
if (key[0].sk_flags & SK_COMMUTE) {
test = (int) (*(key[0].sk_func))
(DatumGetPointer(key[0].sk_argument),

29
src/backend/access/nbtree/nbtsearch.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.4 1996/10/23 07:39:10 scrappy Exp $
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.5 1996/10/30 06:08:01 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
@ -269,6 +269,18 @@ _bt_skeycmp(Relation rel,
&isNull);
keyDatum = entry->sk_argument;
/*
* This may happen in a nested loop if an attribute used
* as scan key is null. DZ 29-10-1996
*/
if ((entry->sk_flags & SK_ISNULL) || (isNull)) {
if ((entry->sk_flags & SK_ISNULL) && (isNull)) {
return (true);
} else {
return (false);
}
}
compare = _bt_invokestrat(rel, i, strat, keyDatum, attrDatum);
if (!compare)
return (false);
@ -501,6 +513,19 @@ _bt_compare(Relation rel,
entry = &scankey[i - 1];
attno = entry->sk_attno;
datum = index_getattr(itup, attno, itupdesc, &null);
/*
* This may happen in a nested loop if an attribute used
* as scan key is null. DZ 29-10-1996
*/
if ((entry->sk_flags & SK_ISNULL) || (null)) {
if ((entry->sk_flags & SK_ISNULL) && (null)) {
return (0);
} else {
return (null ? +1 : -1);
}
}
tmpres = (long) FMGR_PTR2(entry->sk_func, entry->sk_procedure,
entry->sk_argument, datum);
result = tmpres;
@ -641,7 +666,7 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
* hardwired attno == 1.
*/
proc = index_getprocid(rel, 1, BTORDER_PROC);
ScanKeyEntryInitialize(&skdata, 0x0, 1, proc,
ScanKeyEntryInitialize(&skdata, so->keyData[0].sk_flags, 1, proc,
so->keyData[0].sk_argument);
stack = _bt_search(rel, 1, &skdata, &buf);

7
src/backend/executor/nodeIndexscan.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/nodeIndexscan.c,v 1.1.1.1 1996/07/09 06:21:26 scrappy Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/nodeIndexscan.c,v 1.2 1996/10/30 06:08:10 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
@ -273,6 +273,11 @@ ExecIndexReScan(IndexScan *node, ExprContext *exprCtxt, Plan* parent)
scanvalue = (Datum)
ExecEvalExpr(scanexpr, exprCtxt, &isNull, &isDone);
scan_keys[j].sk_argument = scanvalue;
if (isNull) {
scan_keys[j].sk_flags |= SK_ISNULL;
} else {
scan_keys[j].sk_flags &= ~SK_ISNULL;
}
}
}
}