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Re: pg_ctl stop -m immediate on the primary server inflates sequences

From: Boszormenyi Zoltan <zb(at)cybertec(dot)at>
To: Bernd Helmle <mailings(at)oopsware(dot)de>
Cc: pgsql-hackers(at)postgresql(dot)org,Hans-Juergen Schoenig <hs(at)cybertec(dot)at>
Subject: Re: pg_ctl stop -m immediate on the primary server inflates sequences
Date: 2010-04-10 12:36:41
Message-ID: 4BC070D9.10400@cybertec.at (view raw or flat)
Thread:
Lists: pgsql-hackers
Bernd Helmle írta:
>
>
> --On 10. April 2010 09:26:41 +0200 Boszormenyi Zoltan <zb(at)cybertec(dot)at>
> wrote:
>
>> The above is quite reproducable, "pg_ctl stop -m immediate"
>> "usually" inflated my serial sequence, but I had two occasions
>> when not. The 69 -> 70 was one. The inflated increase is always 33:
>
> AFAIKS sequences are pre-logged with 32 values to WAL to avoid
> overhead. I suspect this is why you are seeing those gaps.

Then it should happen all the time, even with "-m fast" or "-m smart", no?

It seemed like my sequences have a CACHE 32 setting, which would
apply to every client that connects, runs nextval() once and disconnects.

But it didn't happen all the time, so it's not deterministic.

-- 
Bible has answers for everything. Proof:
"But let your communication be, Yea, yea; Nay, nay: for whatsoever is more
than these cometh of evil." (Matthew 5:37) - basics of digital technology.
"May your kingdom come" - superficial description of plate tectonics

----------------------------------
Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/


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