Re: Postresql 8.0 Beta 3 - SELECT ... FOR UPDATE

From: Rod Taylor <pg(at)rbt(dot)ca>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: ronzo <m(dot)ronzoni(at)nocerainformatica(dot)net>, PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Postresql 8.0 Beta 3 - SELECT ... FOR UPDATE
Date: 2004-11-25 03:33:45
Message-ID: 1101353625.44437.127.camel@home
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On Wed, 2004-11-24 at 22:13 -0500, Bruce Momjian wrote:
>
> We have discussed this at length and no one could state why having an
> timeout per lock is any better than using a statement_timeout.

Actually, I hit one.

I have a simple queue and a number of processes pulling jobs out of the
queue. Due to transactional requirements, the database is appropriate
for a first cut.

Anyway, a statement_timeout of 100ms is usually plenty to determine that
the job is being processed, and for one of the pollers to move on, but
every once in a while a large job (4 to 5MB chunk of data) would find
itself in the queue which takes more than 100ms to pull out.

Not a big deal, just bump the timeout in this case.

Anyway, it shows a situation where it would be nice to differentiate
between statement_timeout and lock_timeout OR it demonstrates that I
should be using userlocks...

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