[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.
      */