Optimize CleanupTempFiles by having a boolean flag that keeps track of whether

there are FD_XACT_TEMPORARY files to clean up at transaction end.

Per performance profiling results on AWeber's huge systems.

Patch by me after an idea suggested by Simon Riggs.

src/backend/storage/file/fd.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.144 2008/03/10 20:06:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.145 2008/09/19 04:57:10 alvherre Exp $
  *
  * NOTES:
  *
@@ -121,6 +121,12 @@ static int	max_safe_fds = 32;	/* default if not changed */
 #define FD_TEMPORARY		(1 << 0)	/* T = delete when closed */
 #define FD_XACT_TEMPORARY	(1 << 1)	/* T = delete at eoXact */
 
+/*
+ * Flag to tell whether it's worth scanning VfdCache looking for temp files to
+ * close
+ */
+static bool		have_xact_temporary_files = false;
+
 typedef struct vfd
 {
 	int			fd;				/* current FD, or VFD_CLOSED if none */
@@ -889,6 +895,9 @@ OpenTemporaryFile(bool interXact)
 	{
 		VfdCache[file].fdstate |= FD_XACT_TEMPORARY;
 		VfdCache[file].create_subid = GetCurrentSubTransactionId();
+
+		/* ensure cleanup happens at eoxact */
+		have_xact_temporary_files = true;
 	}
 
 	return file;
@@ -1608,7 +1617,7 @@ AtEOSubXact_Files(bool isCommit, SubTransactionId mySubid,
 {
 	Index		i;
 
-	if (SizeVfdCache > 0)
+	if (have_xact_temporary_files)
 	{
 		Assert(FileIsNotOpen(0));		/* Make sure ring not corrupted */
 		for (i = 1; i < SizeVfdCache; i++)
@@ -1684,7 +1693,11 @@ CleanupTempFiles(bool isProcExit)
 {
 	Index		i;
 
-	if (SizeVfdCache > 0)
+	/*
+	 * Careful here: at proc_exit we need extra cleanup, not just
+	 * xact_temporary files.
+	 */
+	if (isProcExit || have_xact_temporary_files)
 	{
 		Assert(FileIsNotOpen(0));		/* Make sure ring not corrupted */
 		for (i = 1; i < SizeVfdCache; i++)
@@ -1702,6 +1715,8 @@ CleanupTempFiles(bool isProcExit)
 					FileClose(i);
 			}
 		}
+
+		have_xact_temporary_files = false;
 	}
 
 	while (numAllocatedDescs > 0)