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Re: Sequences - jumped after power failure

From: Steve T <steve(at)retsol(dot)co(dot)uk>
To: Sean Davis <sdavis2(at)mail(dot)nih(dot)gov>
Cc: PostGreSQL <pgsql-novice(at)postgresql(dot)org>
Subject: Re: Sequences - jumped after power failure
Date: 2008-04-15 10:07:18
Message-ID: 1208254038.27471.288.camel@retsol610 (view raw, whole thread or download thread mbox)
Lists: pgsql-novice
I thought that at first, but there are only a half dozen or so people on
the system. So I would have taken a gap of 3-4 of 'transactions in
progress', but the 33 gap is far too big for that - unless its a caching
issue. I have had no reports of missing data though (and the numbers on
the physical data would seem to echo that it's all ok - ie the 52 rec is
pre crash by about 2-3 mins and the 85 rec is just after the restart).
Typically these tables increase by 30-50 rows a day - so a gap of 33 is
a whole days worth!

I've checked the code this morning and can only find 2 sets of inserts
into the tables in question - one in the manual entry and one in a batch
process. So I checked the batches around that time and nothing was
Totally stumped. I could also have taken 'corruption' on one of the
sequences, but I must have 5 sequences (all related tables in this area)
that all exhibit the same 33 gap. I'm obviously missing something
obvious here, but I just can't see it.

PS the version of PostgreSQL is a bit old - its an 8.0.3
On Tue, 2008-04-15 at 05:47 -0400, Sean Davis wrote:

> On Tue, Apr 15, 2008 at 4:21 AM, Steve T <steve(at)retsol(dot)co(dot)uk> wrote:
> >
> >  Is it possible for a whole set of sequences to suddenly 'jump'?
> >
> >  I have a set of claims tables that cover the claim itself, the customer,
> > contact points etc. Yesterday there was a power failure and the server
> > suffered an immediate power outage. When the server came back, everything
> > seemed fine, apart from the fact that the claim related sequences had all
> > jumped and left a gap of 33 (last was 52 before power failure, next one
> > allocated after power failure 85). This seems consistent across all the
> > tables related to the claim (it may be across the   tables in the database -
> > I haven't checked all of them as yet).
> >
> >  Does this sound feasible and if so, what is the cause?
> One explanation: if there were uncommitted transactions at the time of
> the power failure, the sequence would have been advanced, but the
> corresponding rows would not have entered the database.
> Sean

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