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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: Martijn van Oosterhout <kleptog(at)svana(dot)org>
Cc: Bernd Helmle <mailings(at)oopsware(dot)de>,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: 2010-04-12 08:07:17
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Lists: pgsql-hackers
Martijn van Oosterhout írta:
> On Sat, Apr 10, 2010 at 02:36:41PM +0200, Boszormenyi Zoltan 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?
> Nope, because on a normal shutdown it writes out the actual value. When
> you say "immediate" you mean "right now, don't bother with anything not
> important", like for example gaps in sequences. You're essentially
> crashing the DB.
> Have a ncie day,

OK, thanks for the info.

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

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