Move btbulkdelete's vacuum_delay_point() call to a place in the loop where

we are not holding a buffer content lock; where it was, InterruptHoldoffCount
is positive and so we'd not respond to cancel signals as intended.  Also
add missing vacuum_delay_point() call in btvacuumcleanup.  This should fix
complaint from Evgeny Gridasov about failure to respond to SIGINT/SIGTERM
in a timely fashion (bug #2257).

src/backend/access/nbtree/nbtree.c

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.140 2006/02/12 00:18:17 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.141 2006/02/14 17:20:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -580,8 +580,6 @@ btbulkdelete(PG_FUNCTION_ARGS)
 						maxoff;
 			BlockNumber nextpage;
 
-			vacuum_delay_point();
-
 			ndeletable = 0;
 			page = BufferGetPage(buf);
 			opaque = (BTPageOpaque) PageGetSpecialPointer(page);
@@ -638,6 +636,10 @@ btbulkdelete(PG_FUNCTION_ARGS)
 			}
 			else
 				_bt_relbuf(rel, buf);
+
+			/* call vacuum_delay_point while not holding any buffer lock */
+			vacuum_delay_point();
+
 			/* And advance to next page, if any */
 			if (nextpage == P_NONE)
 				break;
@@ -732,6 +734,8 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
 		Page		page;
 		BTPageOpaque opaque;
 
+		vacuum_delay_point();
+
 		/*
 		 * We can't use _bt_getbuf() here because it always applies
 		 * _bt_checkpage(), which will barf on an all-zero page. We want to