Subject: Re: compute_query_id and pg_stat_statements
To: Alvaro Herrera <alvherre@alvh.no-ip.org>,
 Julien Rouhaud <rjuju123@gmail.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>,
 Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
 Magnus Hagander <magnus@hagander.net>, Michael Paquier
 <michael@paquier.xyz>, Andres Freund <andres@anarazel.de>,
 Tom Lane <tgl@sss.pgh.pa.us>, Stephen Frost <sfrost@snowman.net>,
 Bruce Momjian <bruce@momjian.us>, Christoph Berg <myon@debian.org>,
 Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: <20210514000437.GA14223@alvherre.pgsql>
From: Fujii Masao <masao.fujii@oss.nttdata.com>
Message-ID: <63caca55-a48b-a8b4-9c17-814a7106e035@oss.nttdata.com>
Date: Fri, 14 May 2021 12:20:00 +0900
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On 2021/05/14 9:04, Alvaro Herrera wrote:
> Here's a first attempt at what was suggested.  If you say "auto" it
> remains auto in SHOW, but it gets enabled if a module asks for it.
> 
> Not final yet, but I thought I'd throw it out for early commentary ...

Many thanks! The patch basically looks good to me.

+void
+EnableQueryId(void)
+{
+	if (compute_query_id == COMPUTE_QUERY_ID_AUTO)
+		auto_query_id_enabled = true;

Shouldn't EnableQueryId() enable auto_query_id_enabled whatever compute_query_id is?
Otherwise, for example, the following scenario can happen and it's a bit strange.

1. The server starts up with shared_preload_libraries=pg_stat_statements and compute_query_id=on
2. compute_query_id is set to auto and the configuration file is reloaded
Then, even though compute_query_id is auto and pg_stat_statements is loaded,
query ids are not computed and no queries are tracked by pg_stat_statements.


Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION