From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Yun Li <liyunjuanyong@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Feature improvement: can we add queryId for
 pg_catalog.pg_stat_activity view?
In-reply-to: 
 <CA+TgmobNUwzTnb6f5Kmw=qSXXs2sMexerd8uTyaHE2CG9=F=SQ@mail.gmail.com>
References: 
 <CA+8PKvQnMfOE-c3YLRwxOsCYXQDyP8VXs6CDtMZp1V4=D4LuFA@mail.gmail.com>
 <21800.1552701008@sss.pgh.pa.us>
 <CA+TgmobNUwzTnb6f5Kmw=qSXXs2sMexerd8uTyaHE2CG9=F=SQ@mail.gmail.com>
Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Sat, 16 Mar 2019 10:32:16 -0400"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <28190.1552753201.1@sss.pgh.pa.us>
Date: Sat, 16 Mar 2019 12:20:01 -0400
Message-ID: <28191.1552753201@sss.pgh.pa.us>
Precedence: bulk

Robert Haas <robertmhaas@gmail.com> writes:
> On Fri, Mar 15, 2019 at 9:50 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> pg_stat_statements has a notion of query ID, but that notion might be
>> quite inappropriate for other usages, which is why it's an extension
>> and not core.

> Having written an extension that also wanted a query ID, I disagree
> with this position.

[ shrug... ]  The fact remains that pg_stat_statements's definition is
pretty lame.  There's a lot of judgment calls in which query fields
it chooses to examine or ignore, and there's been no attempt at all
to make the ID PG-version-independent, and I rather doubt that it's
platform-independent either.  Nor will the IDs survive a dump/reload
even on the same server, since object OIDs will likely change.

These things are OK, or at least mostly tolerable, for pg_stat_statements'
usage ... but I don't think it's a good idea to have the core code
dictating that definition to all extensions.  Right now, if you have
an extension that needs some other query-ID definition, you can do it,
you just can't run that extension alongside pg_stat_statements.
But you'll be out of luck if the core code starts filling that field.

I'd be happier about having the core code compute a query ID if we
had a definition that was not so obviously slapped together.

			regards, tom lane