Fix UPDATE/DELETE WHERE CURRENT OF to support repeated update and update-

then-delete on the current cursor row.  The basic fix is that nodeTidscan.c
has to apply heap_get_latest_tid() to the current-scan-TID obtained from the
cursor query; this ensures we get the latest row version to work with.
However, since that only works if the query plan is a TID scan, we also have
to hack the planner to make sure only that type of plan will be selected.
(Formerly, the planner might decide to apply a seqscan if the table is very
small.  This change is probably a Good Thing anyway, since it's hard to see
how a seqscan could really win.)  That means the execQual.c code to support
CurrentOfExpr as a regular expression type is dead code, so replace it with
just an elog().  Also, add regression tests covering these cases.  Note
that the added tests expose the fact that re-fetching an updated row
misbehaves if the cursor used FOR UPDATE.  That's an independent bug that
should be fixed later.  Per report from Dharmendra Goyal.

1 files changed, 6 insertions, 34 deletions

diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c
index cc165006f5c..53ddc658197 100644
--- a/src/backend/executor/execQual.c
+++ b/src/backend/executor/execQual.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.222 2007/09/06 17:31:58 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.223 2007/10/24 18:37:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3694,45 +3694,17 @@ ExecEvalArrayCoerceExpr(ArrayCoerceExprState *astate,
 /* ----------------------------------------------------------------
  *		ExecEvalCurrentOfExpr
  *
- * Normally, the planner will convert CURRENT OF into a TidScan qualification,
- * but we have plain execQual support in case it doesn't.
+ * The planner must convert CURRENT OF into a TidScan qualification.
+ * So, we have to be able to do ExecInitExpr on a CurrentOfExpr,
+ * but we shouldn't ever actually execute it.
  * ----------------------------------------------------------------
  */
 static Datum
 ExecEvalCurrentOfExpr(ExprState *exprstate, ExprContext *econtext,
 					  bool *isNull, ExprDoneCond *isDone)
 {
-	CurrentOfExpr *cexpr = (CurrentOfExpr *) exprstate->expr;
-	bool	result;
-	bool	lisnull;
-	Oid		tableoid;
-	ItemPointer tuple_tid;
-	ItemPointerData cursor_tid;
-
-	if (isDone)
-		*isDone = ExprSingleResult;
-	*isNull = false;
-
-	Assert(cexpr->cvarno != INNER);
-	Assert(cexpr->cvarno != OUTER);
-	Assert(!TupIsNull(econtext->ecxt_scantuple));
-	/* Use slot_getattr to catch any possible mistakes */
-	tableoid = DatumGetObjectId(slot_getattr(econtext->ecxt_scantuple,
-											 TableOidAttributeNumber,
-											 &lisnull));
-	Assert(!lisnull);
-	tuple_tid = (ItemPointer)
-		DatumGetPointer(slot_getattr(econtext->ecxt_scantuple,
-									 SelfItemPointerAttributeNumber,
-									 &lisnull));
-	Assert(!lisnull);
-
-	if (execCurrentOf(cexpr, econtext, tableoid, &cursor_tid))
-		result = ItemPointerEquals(&cursor_tid, tuple_tid);
-	else
-		result = false;
-
-	return BoolGetDatum(result);
+	elog(ERROR, "CURRENT OF cannot be executed");
+	return 0;					/* keep compiler quiet */
 }