Re: Patch to send transaction commit/rollback stats to the stats collector unconditionally.

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Gurjeet Singh <gurjeet(at)singh(dot)im>, PGSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Patch to send transaction commit/rollback stats to the stats collector unconditionally.
Date: 2014-03-19 23:27:52
Message-ID: 12754.1395271672@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> I'm not sure I understand the point of this whole thing. Realistically,
> how many transactions are there that do not access any database tables?

I think that something like "select * from pg_stat_activity" might not
bump any table-access counters, once the relevant syscache entries had
gotten loaded. You could imagine that a monitoring app would do a long
series of those and nothing else (whether any actually do or not is a
different question).

But still, it's a bit hard to credit that this patch is solving any real
problem. Where's the user complaints about the existing behavior?
That is, even granting that anybody has a workload that acts like this,
why would they care ... and are they prepared to take a performance hit
to avoid the counter jump after the monitoring app exits?

regards, tom lane

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