Re: Unsupported effective_io_concurrency platforms

Bruce Momjian wrote:
> Tom Lane wrote:
> > Peter Eisentraut <peter_e@gmx.net> writes:
> > > Joshua D. Drake wrote:
> > > Do we want to give a more informative error message, like "not supported
> > > on this platform?"
> >
> > > The trick will be to fit this into the GUC framework.
> >
> > You could do it by enforcing the limit in an assign hook, but I'm
> > not convinced it's worth the trouble.
>
> I have created a patch to at least display a more helpful message,
> without being specific:
>
>     test=> set effective_io_concurrency = 1;
>     ERROR:  parameter "effective_io_concurrency" cannot be changed from 0

I fixed this an easier way, by making the parameter PGC_INTERNAL on
systems that don't have posix_fadvise().

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +
Index: src/backend/utils/misc/guc.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v
retrieving revision 1.497
diff -c -c -r1.497 guc.c
*** src/backend/utils/misc/guc.c    9 Mar 2009 14:34:34 -0000    1.497
--- src/backend/utils/misc/guc.c    2 Apr 2009 19:52:49 -0000
***************
*** 1713,1719 ****
      },

      {
!         {"effective_io_concurrency", PGC_USERSET, RESOURCES,
              gettext_noop("Number of simultaneous requests that can be handled efficiently by the disk subsystem."),
              gettext_noop("For RAID arrays, this should be approximately the number of drive spindles in the array.")
          },
--- 1713,1725 ----
      },

      {
!         {"effective_io_concurrency",
! #ifdef USE_PREFETCH
!         PGC_USERSET,
! #else
!         PGC_INTERNAL,
! #endif
!         RESOURCES,
              gettext_noop("Number of simultaneous requests that can be handled efficiently by the disk subsystem."),
              gettext_noop("For RAID arrays, this should be approximately the number of drive spindles in the array.")
          },