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, 3 insertions, 1 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 82f851eeacc..fbb07feae7e 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.178 2007/09/20 17:56:32 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.179 2007/10/24 18:37:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1087,6 +1087,7 @@ typedef struct BitmapHeapScanState
 /* ----------------
  *	 TidScanState information
  *
+ *		isCurrentOf	   scan has a CurrentOfExpr qual
  *		NumTids		   number of tids in this scan
  *		TidPtr		   index of currently fetched tid
  *		TidList		   evaluated item pointers (array of size NumTids)
@@ -1096,6 +1097,7 @@ typedef struct TidScanState
 {
 	ScanState	ss;				/* its first field is NodeTag */
 	List	   *tss_tidquals;	/* list of ExprState nodes */
+	bool		tss_isCurrentOf;
 	int			tss_NumTids;
 	int			tss_TidPtr;
 	int			tss_MarkTidPtr;