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>

diff --git a/src/backend/access/common/heapvalid.c b/src/backend/access/common/heapvalid.c
index 45003095b237ca0eb64f2d8fd891b92f2ee6ceaa..c50700c2036690c5b41f7bc4ca98c61fbbd5e677 100644 (file)
--- a/src/backend/access/common/heapvalid.c
+++ b/src/backend/access/common/heapvalid.c
@@ -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);

diff --git a/src/backend/access/common/indexvalid.c b/src/backend/access/common/indexvalid.c
index b5854db569724c36487db00c7313a869fa1f94bd..23b3437460fd7bcf32f50e9f5f3693276be37d94 100644 (file)
--- a/src/backend/access/common/indexvalid.c
+++ b/src/backend/access/common/indexvalid.c
@@ -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),

diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c
index 4551afbf05a52e5d0c55633d39c1f0226f5e86c6..3d3ff08524767a80960564376d7d7bae30c1f165 100644 (file)
--- a/src/backend/access/nbtree/nbtsearch.c
+++ b/src/backend/access/nbtree/nbtsearch.c
@@ -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);

diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index 758fabdefe5278f6832235b6c828cbe5274e2e5a..b8acb7897b473e41af2be7b5f5aeada333962c67 100644 (file)
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -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;
+               }
            }
        }
     }