Re: shmget error text reports funny max_connections numbers

I have applied a patch to improve shared memory failure reporting,
attached.  We no longer report actual parameter _values_ and suggest
that other parameters might also cause such failures.

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Alvaro Herrera wrote:
> Excerpts from Robert Haas's message of jue oct 14 21:36:48 -0300 2010:
> > On Wed, Oct 13, 2010 at 2:39 PM, Peter Eisentraut <peter_e@gmx.net> wrote:
> > > Since MaxBackends is actually max_connections + autovacuum_max_workers +
> > > 1, when you get an error message from shmget() it will tell you
> > >
> > > "reduce ... its max_connections parameter (currently 104)"
> > >
> > > when you actually set
> > >
> > > max_connections = 100
> > >
> > > This looks a bit silly.
> > >
> > > Should we just make the error messages report MaxBackends -
> > > autovacuum_max_workers - 1, or is it worthwhile calling out
> > > autovacuum_max_workers separately?
> > 
> > I suppose there are other reasons we could run out of shared memory,
> > too.  max_locks_per_transaction, for example.  It might be good to
> > revise the wording of the message so as to suggest that these are only
> > some of the possible causes.
> 
> Agreed.  Something like "reduce one or more of the following parameters:
> shared_buffers (currently NN), max_connections (currently NN),
> autovacuum_max_workers (currently MM), 
> 
> I also suggest that it would be good to revise these things so that
> sentences within those monstruous paragraphs can be translated
> separately.  Maybe changing the ErrorData stuff so that there can be
> more than one errhint field?  If that's too much trouble, perhaps having
> "%s. %s. %s. %s" as the first errhint parameter, and have each sentence
> be its own translatable unit.
> 
> I also just noticed that we use stars for emphasis here, "This error
> does *not* mean..." which is maybe too cute.
> 
> -- 
> lvaro Herrera <alvherre@commandprompt.com>
> The PostgreSQL Company - Command Prompt, Inc.
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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
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