Re: tuple statistics update

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Tom DalPozzo <t(dot)dalpozzo(at)gmail(dot)com>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: tuple statistics update
Date: 2017-04-19 14:37:50
Message-ID: 7294.1492612670@sss.pgh.pa.us
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Tom DalPozzo <t(dot)dalpozzo(at)gmail(dot)com> writes:
> 2017-04-18 22:06 GMT+02:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>> If your session is just sitting, that's not surprising. I think stats
>> updates are only transmitted to the collector at transaction end (and
>> even then, only if it's been at least N msec since the last transmission
>> from the current session).

> Hi, my transaction ended, that I waited 1 min and queried the stat.
> I had to wait for session end in order to see the updeted stats.
> Did you mean "...to the collector at SESSION end"?

No, I meant what I said. No amount of just-sitting will cause a session
to do something: it either transmits stats at transaction end or it
doesn't because it thinks it's too soon since its last update. If you
want to force out the stats, you could wait a second or so and then
do a dummy transaction (even "select 1" will do, in testing).

BTW, a quick look at the code says the threshold is 500 msec, ie,
stats are sent only if it's been at least half a second since the
session's last report.

regards, tom lane

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