Re: Unlogged tables, persistent kind

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Jesper Krogh" <jesper(at)krogh(dot)cc>,<pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Unlogged tables, persistent kind
Date: 2011-04-25 18:12:27
Message-ID: 4DB5733B020000250003CDBD@gw.wicourts.gov
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Jesper Krogh <jesper(at)krogh(dot)cc> wrote:
> On 2011-04-25 20:00, Leonardo Francalanci wrote:
>>> The amount of data loss on a big table will be <1% of the data
>>> loss caused by truncating the whole table.
>>
>> If that 1% is random (not time/transaction related), usually
>> you'd rather have an empty table. In other words: is a table
>> that is not consistant with anything else in the db useful?
>>
> Depends on the application, if it serves for pure caching then it
> is fully acceptable and way better than dropping everything.

I buy this *if* we can be sure we're not keeping information which
is duplicated or mangled, and if we can avoid crashing the server to
a panic because of broken pointers or other infelicities. I'm not
sure that can't be done, but I don't think I've heard an explanation
of how that could be accomplished, particularly without overhead
which would wipe out the performance benefit of unlogged tables.
(And without a performance benefit, what's the point?)

-Kevin

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