Fix LIMIT/OFFSET for null limit values. This worked before 8.2 but was broken

by the change to make limit values int8 instead of int4.  (Specifically, you
can do DatumGetInt32 safely on a null value, but not DatumGetInt64.)  Per
bug #2803 from Greg Johnson.

diff --git a/src/backend/executor/nodeLimit.c b/src/backend/executor/nodeLimit.c
index 935b59a722391f16b59c01fd551d4b2b761a6645..8455375c60239beaa66a166f3bf25c2205966383 100644 (file)
--- a/src/backend/executor/nodeLimit.c
+++ b/src/backend/executor/nodeLimit.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/executor/nodeLimit.c,v 1.27 2006/07/26 19:31:50 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/executor/nodeLimit.c,v 1.28 2006/12/03 21:40:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -225,20 +225,24 @@ static void
 recompute_limits(LimitState *node)
 {
        ExprContext *econtext = node->ps.ps_ExprContext;
+       Datum           val;
        bool            isNull;
 
        if (node->limitOffset)
        {
-               node->offset =
-                       DatumGetInt64(ExecEvalExprSwitchContext(node->limitOffset,
-                                                                                                       econtext,
-                                                                                                       &isNull,
-                                                                                                       NULL));
+               val = ExecEvalExprSwitchContext(node->limitOffset,
+                                                                               econtext,
+                                                                               &isNull,
+                                                                               NULL);
                /* Interpret NULL offset as no offset */
                if (isNull)
                        node->offset = 0;
-               else if (node->offset < 0)
-                       node->offset = 0;
+               else
+               {
+                       node->offset = DatumGetInt64(val);
+                       if (node->offset < 0)
+                               node->offset = 0;
+               }
        }
        else
        {
@@ -248,17 +252,23 @@ recompute_limits(LimitState *node)
 
        if (node->limitCount)
        {
-               node->noCount = false;
-               node->count =
-                       DatumGetInt64(ExecEvalExprSwitchContext(node->limitCount,
-                                                                                                       econtext,
-                                                                                                       &isNull,
-                                                                                                       NULL));
+               val = ExecEvalExprSwitchContext(node->limitCount,
+                                                                               econtext,
+                                                                               &isNull,
+                                                                               NULL);
                /* Interpret NULL count as no count (LIMIT ALL) */
                if (isNull)
-                       node->noCount = true;
-               else if (node->count < 0)
+               {
                        node->count = 0;
+                       node->noCount = true;
+               }
+               else
+               {
+                       node->count = DatumGetInt64(val);
+                       if (node->count < 0)
+                               node->count = 0;
+                       node->noCount = false;
+               }
        }
        else
        {