From 46a0eee3006b11a15b73426c8146ed5ab32e1d62 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 28 Aug 2005 22:47:20 +0000
Subject: Tweak nodeBitmapAnd to stop evaluating sub-plan scans if it finds
 it's got an empty bitmap after any step; the remaining subplans can no longer
 affect the result.  Per a suggestion from Ilia Kantor.

---
 src/backend/nodes/tidbitmap.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

(limited to 'src/backend/nodes/tidbitmap.c')

diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index 777bf6482d..e36a8d9806 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -23,7 +23,7 @@
  * Copyright (c) 2003-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.5 2005/07/24 02:25:26 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.6 2005/08/28 22:47:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -510,6 +510,15 @@ tbm_intersect_page(TIDBitmap *a, PagetableEntry *apage, const TIDBitmap *b)
 	}
 }
 
+/*
+ * tbm_is_empty - is a TIDBitmap completely empty?
+ */
+bool
+tbm_is_empty(const TIDBitmap *tbm)
+{
+	return (tbm->nentries == 0);
+}
+
 /*
  * tbm_begin_iterate - prepare to iterate through a TIDBitmap
  *
-- 
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