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Re: NOLOGGING option, or ?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Greg Stark <gsstark(at)mit(dot)edu>, Neil Conway <neilc(at)samurai(dot)com>,Alvaro Herrera <alvherre(at)surnet(dot)cl>,Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: NOLOGGING option, or ?
Date: 2005-06-01 22:32:32
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Lists: pgsql-hackers
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> One idea would be to look at the table file size first.  If it has zero
> blocks, lock the table and if it still has zero blocks, do the no-WAL
> copy.

I think that's a bad idea.  It would make the behavior unpredictable
--- sometimes a COPY will take an exclusive lock, and other times not;
and the reason why is at a lower semantic level than the user is
supposed to know about.

Before you say "this is not important", consider the nontrivial risk
that the stronger lock will cause a deadlock failure.  I don't think
that it's acceptable for lock strength to be unpredictable.

			regards, tom lane

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