From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 10 Feb 2008 20:39:08 +0000 (+0000)
Subject: Fix PageGetExactFreeSpace() so that it actually behaves sensibly
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=9524d735275d7f5869a11b84bc437efa839ea38c;p=users%2Fbernd%2Fpostgres.git

Fix PageGetExactFreeSpace() so that it actually behaves sensibly
if pd_lower > pd_upper, rather than merely claiming to.  This would
only matter if the page header were corrupt, which shouldn't occur,
but ...
---

diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c
index f34dd7e7b7..eea03deaa7 100644
--- a/src/backend/storage/page/bufpage.c
+++ b/src/backend/storage/page/bufpage.c
@@ -489,6 +489,9 @@ PageGetExactFreeSpace(Page page)
 	space = (int) ((PageHeader) page)->pd_upper -
 		(int) ((PageHeader) page)->pd_lower;
 
+	if (space < 0)
+		return 0;
+
 	return (Size) space;
 }