Subject: Re: explain plans with information about (modified) gucs
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Sergei Agalakov <sergei.agalakov@gmail.com>, pgsql-hackers@postgresql.org
References: <201901142213.gt7vdg65pp4d@alvherre.pgsql>
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <c76b7ec7-70db-6ec9-cc1a-73ffb53f6b2e@2ndquadrant.com>
Date: Tue, 15 Jan 2019 02:39:49 +0100
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On 1/14/19 11:13 PM, Alvaro Herrera wrote:
> On 2019-Jan-14, Tomas Vondra wrote:
> 
>> The one slightly annoying issue is that currently all the options are
>> formatted as text, including e.g. cpu_tuple_cost. That's because the GUC
>> options may have show hook, so I can't access the value directly (not
>> sure if there's an option around it).
> 
> I think the problem is that you'd have to know how to print the value,
> which can be in one of several different C types.  You'd have to grow
> some more infrastructure in the GUC tables, I think, and that doesn't
> seem worth the trouble.  Printing as text seems enough.
> 

I don't think the number of formats is such a big issue - the range of
formats is quite limited: PGC_BOOL, PGC_INT, PGC_REAL, PGC_STRING and
PGC_ENUM. But the show hook simply returns string, and I'm not sure it's
guaranteed it matches the raw value (afaik the assign/show hooks can do
all kinds of funny stuff).

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services