[PATCH] Don't bail with legitimate -N/-B options

Greetings,

Starting PostgreSQL 8.3.0 with the default options used by Gentoo Linux 
(-N 40 -B 80) causes it to bail with an error message.

"the number of buffers (-B) must be at least twice the number of allowed 
connections (-N) and at least 16"

The problem is that NBuffers is actually "max autovacuum connections" + 
NBuffers.

My attached patch fixes this by adding "max autovacuum connections" * 2 
to NBuffers before the check.

Best regards,
Andreas Kling
ACG Nyström AB
Index: src/backend/postmaster/postmaster.c
===================================================================
--- src/backend/postmaster/postmaster.c	(revision 30129)
+++ src/backend/postmaster/postmaster.c	(working copy)
@@ -685,6 +685,9 @@ PostmasterMain(int argc, char *argv[])
 	/* And switch working directory into it */
 	ChangeToDataDir();
 
+	/* Add buffers to accomodate backends "reserved" for autovacuum */
+	NBuffers += autovacuum_max_workers * 2;
+
 	/*
 	 * Check for invalid combinations of GUC settings.
 	 */