From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
---|---|
To: | Craig Ringer <ringerc(at)ringerc(dot)id(dot)au> |
Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [PATCH] Docs: Make notes on sequences and rollback more obvious |
Date: | 2012-08-18 19:01:49 |
Message-ID: | CAMkU=1y7eyBQo0h=DLrsmXRKrq5pgpHZ6WyqwX=D+M3wmxwhDg@mail.gmail.com |
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On Sat, Aug 18, 2012 at 1:34 AM, Craig Ringer <ringerc(at)ringerc(dot)id(dot)au> wrote:
> On 08/07/2012 09:45 PM, Kevin Grittner wrote:
>>
>> I also think it's a problem that one can get through the entire
>> "Concurrency Control" chapter (mvcc.sgml) without a clue that
>> sequences aren't transactional. I think maybe a mention in the
>> Introduction section of that chapter with a <ref> would be
>> appropriate.
>
>
> How about this? Is it accurate to suggest that sequences behave as if they
> were always in "dirty read" isolation?
I don't think so. I would think that a dirty read would allow
unresolved data to be visible, but upon rollback of the other
transaction would stop seeing the "dirty" data. That doesn't describe
sequences. A better explanation is that sequence advancement is
autonomously committed.
> Or would you instead say that
> "changes made to a sequence are immediately visible to all other
> transactions" ?
Yes, that sounds better.
Cheers,
Jeff
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