Re: explaining "context" column of pg_settings

On Thu, Dec 16, 2010 at 7:11 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Josh Kupershmidt <schmiddy@gmail.com> writes:
> I did some work on this patch and attach an updated version.

Thanks for taking a look at this. Your version is much more clear.

> I'm not
> however convinced that it's a good idea to bury this material in
> catalogs.sgml --- I think few people ever read that chapter.  Shouldn't
> we put this into config.sgml instead, somewhere in section 18.1?

Yeah, that seems like a better place for this text.

>> I avoided just copy-pasting from guc.h, particulary because some of
>> the explanations struck me as confusing or incorrect.
>
> Well, your replacement explanations seemed even less correct ;-).
> Also, I think what the text needs to emphasize is *how* to change
> each setting type, so that prompted some of my editing.

One piece in my patch which isn't in your version is this bit:

+     ... You may also
+     send a <systemitem>SIGHUP</systemitem> to an individual backend to cause
+     only that backend to reload <filename>postgresql.conf</filename>.

I was rather surprised when I learned this from the description in
guc.h of SIGHUP options. I tested by altering "full_page_writes" in
postgresql.conf and sending a SIGHUP to one backend, and sure enough
that backend picked up the change but new backends didn't. Unless this
feature is documented somewhere else, I think it would be helpful to
keep a snippet like this.

Josh