| 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 |
| Message-ID: | 21427.1117665152@sss.pgh.pa.us |
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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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