Fix a race condition that caused pg_database_size() and pg_tablespace_size()

to fail if an object was removed between calls to ReadDir() and stat().
Per discussion in pgsql-hackers.

http://archives.postgresql.org/pgsql-hackers/2007-03/msg00671.php

Bug report and patch by Michael Fuhr.

src/backend/utils/adt/dbsize.c

@@ -5,7 +5,7 @@
  * Copyright (c) 2002-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/dbsize.c,v 1.7 2005/10/29 00:31:51 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/dbsize.c,v 1.7.2.1 2007/03/11 06:43:23 alvherre Exp $
  *
  */
 
@@ -51,10 +51,14 @@ db_dir_size(const char *path)
 		snprintf(filename, MAXPGPATH, "%s/%s", path, direntry->d_name);
 
 		if (stat(filename, &fst) < 0)
+		{
+			if (errno == ENOENT)
+				continue;
+			else
 				ereport(ERROR,
 						(errcode_for_file_access(),
 						 errmsg("could not stat file \"%s\": %m", filename)));
-
+		}
 		dirsize += fst.st_size;
 	}
 
@@ -173,9 +177,14 @@ calculate_tablespace_size(Oid tblspcOid)
 		snprintf(pathname, MAXPGPATH, "%s/%s", tblspcPath, direntry->d_name);
 
 		if (stat(pathname, &fst) < 0)
+		{
+			if (errno == ENOENT)
+				continue;
+			else
 				ereport(ERROR,
 						(errcode_for_file_access(),
 						 errmsg("could not stat file \"%s\": %m", pathname)));
+		}
 
 		if (fst.st_mode & S_IFDIR)
 			totalsize += db_dir_size(pathname);