Re: wal_buffers = -1 and SIGHUP

On Thu, Mar 31, 2011 at 8:38 AM, Bernd Helmle <mailings(at)oopsware(dot)de> wrote:
> This might be nitpicking (or i'm currently missing something), but i
> recognized that setting wal_buffers = -1 always triggers the following on
> reload, even if nothing to wal_buffers had changed:
>
> $ pg_ctl reload
> LOG:  received SIGHUP, reloading configuration files
> LOG:  parameter "wal_buffers" cannot be changed without restarting the
> server
>
> This only happens when you have wal_buffers set to -1.

This is a bug. The root cause is that, on startup, we do this:

if (xbuffers != XLOGbuffers)
{
snprintf(buf, sizeof(buf), "%d", xbuffers);
SetConfigOption("wal_buffers", buf, PGC_POSTMASTER,
PGC_S_OVERRIDE);
}

I had intended to commit Greg's patch with a show hook and an assign
hook and the calculated value stored separately from the GUC variable,
which I believe would avoid this is a problem, but Tom thought this
way was better. Unfortunately, my knowledge of the GUC machinery is
insufficient to think of a way to avoid it, other than the one Tom
already rejected.

--
Robert Haas
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