Re: Using multi-row technique with COPY

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: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Using multi-row technique with COPY
Date: 2005-11-29 19:30:28
Message-ID: 9120.1133292628@sss.pgh.pa.us
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Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> One idea for default behavior would be to use EXCLUSIVE when the table
> is zero size. I think that would do pg_dump and most of the user cases,
> and of course users could override the default by using a keyword. We
> could emit a NOTICE if an an exclusive lock is used without an EXCLUSIVE
> keyword. One problem I see is that there is no way to insure zero size
> without a lock that blocks other writers. Is that reliable?

No, and if you try to upgrade your lock after checking, you create a
deadlock problem.

Something that would probably be reasonable, and require *no* weird new
syntax, is to shortcut in a COPY into a table created in the current
transaction. I believe we still keep a flag in the relcache indicating
whether that's the case ...

regards, tom lane

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