From c29a9c37bf6bdaaaa65ccbcd4c69c596691134e1 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 24 Oct 2007 18:37:09 +0000
Subject: 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.

---
 src/backend/executor/execQual.c | 40 ++++++----------------------------------
 1 file changed, 6 insertions(+), 34 deletions(-)

(limited to 'src/backend/executor/execQual.c')

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 */
 }
 
 
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