Index: src/backend/executor/execCurrent.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/executor/execCurrent.c,v
retrieving revision 1.7
diff -c -r1.7 execCurrent.c
*** src/backend/executor/execCurrent.c	12 May 2008 00:00:48 -0000	1.7
--- src/backend/executor/execCurrent.c	15 Nov 2008 00:04:17 -0000
***************
*** 46,51 ****
--- 46,53 ----
  	char	   *table_name;
  	Portal		portal;
  	QueryDesc  *queryDesc;
+ 	ExecRowMark *erm;
+ 	ListCell   *lc;
  	ScanState  *scanstate;
  	bool		lisnull;
  	Oid			tuple_tableoid;
***************
*** 86,91 ****
--- 88,140 ----
  						cursor_name)));
  
  	/*
+ 	 * If the query uses FOR UPDATE, look through the executor's state for that
+ 	 * to see if we can identify the target row that way.  We succeed if there
+ 	 * is exactly one FOR UPDATE item for the requested table.  (Note:
+ 	 * presently, FOR UPDATE is not allowed on inheritance trees, so there is
+ 	 * no need to worry about whether a FOR UPDATE item is currently valid.)
+ 	 */
+ 	erm = NULL;
+ 	foreach(lc, queryDesc->estate->es_rowMarks)
+ 	{
+ 		ExecRowMark *thiserm = (ExecRowMark *) lfirst(lc);
+ 
+ 		if (RelationGetRelid(thiserm->relation) == table_oid)
+ 		{
+ 			if (erm)
+ 			{
+ 				/* multiple references to desired relation */
+ 				erm = NULL;
+ 				break;
+ 			}
+ 			erm = thiserm;
+ 		}
+ 	}
+ 
+ 	if (erm)
+ 	{
+ 		/*
+ 		 * Okay, we were able to identify the target FOR UPDATE item.
+ 		 *
+ 		 * The cursor must have a current result row: per the SQL spec, it's
+ 		 * an error if not.
+ 		 */
+ 		if (portal->atStart || portal->atEnd)
+ 			ereport(ERROR,
+ 					(errcode(ERRCODE_INVALID_CURSOR_STATE),
+ 					 errmsg("cursor \"%s\" is not positioned on a row",
+ 							cursor_name)));
+ 		/* Return the currently scanned TID */
+ 		if (ItemPointerIsValid(&(erm->curCtid)))
+ 		{
+ 			*current_tid = erm->curCtid;
+ 			return true;
+ 		}
+ 		/* Inactive scan?  Probably can't happen at the moment */
+ 		return false;
+ 	}
+ 
+ 	/*
  	 * Dig through the cursor's plan to find the scan node.  Fail if it's not
  	 * there or buried underneath aggregation.
  	 */
Index: src/backend/executor/execMain.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/executor/execMain.c,v
retrieving revision 1.315
diff -c -r1.315 execMain.c
*** src/backend/executor/execMain.c	6 Nov 2008 20:51:14 -0000	1.315
--- src/backend/executor/execMain.c	15 Nov 2008 00:04:17 -0000
***************
*** 602,607 ****
--- 602,608 ----
  		erm->noWait = rc->noWait;
  		/* We'll set up ctidAttno below */
  		erm->ctidAttNo = InvalidAttrNumber;
+ 		ItemPointerSetInvalid(&(erm->curCtid));
  		estate->es_rowMarks = lappend(estate->es_rowMarks, erm);
  	}
  
***************
*** 1442,1447 ****
--- 1443,1451 ----
  							elog(ERROR, "unrecognized heap_lock_tuple status: %u",
  								 test);
  					}
+ 
+ 					/* Remember tuple TID for WHERE CURRENT OF */
+ 					erm->curCtid = tuple.t_self;
  				}
  			}
  
Index: src/include/nodes/execnodes.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/nodes/execnodes.h,v
retrieving revision 1.194
diff -c -r1.194 execnodes.h
*** src/include/nodes/execnodes.h	31 Oct 2008 19:37:56 -0000	1.194
--- src/include/nodes/execnodes.h	15 Nov 2008 00:04:17 -0000
***************
*** 376,381 ****
--- 376,382 ----
  	bool		forUpdate;		/* true = FOR UPDATE, false = FOR SHARE */
  	bool		noWait;			/* NOWAIT option */
  	AttrNumber	ctidAttNo;		/* resno of its ctid junk attribute */
+ 	ItemPointerData curCtid;	/* ctid of currently locked tuple */
  } ExecRowMark;