Re: Concurrency and locks

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Mike Mascari" <mascarm(at)mascari(dot)com>
Cc: "PostgreSQL-General-List (E-mail)" <pgsql-general(at)postgresql(dot)org>
Subject: Re: Concurrency and locks
Date: 2003-02-19 17:00:39
Message-ID: 12139.1045674039@sss.pgh.pa.us
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"Mike Mascari" <mascarm(at)mascari(dot)com> writes:
> If one wants to guarantee consistency in user-defined BEFORE
> INSERT/UPDATE triggers and trigger procedures, at the moment, is
> the only recourse SELECT FOR UPDATE? Is this the cause of
> performance problems with the current RI implementation?

Yup, and yup (or at least one cause). But it's not easy to see how
to build a multiple-locker mechanism that scales to handle very large
numbers of locked tuples. You can't really expect to keep the state
data in shared memory --- but if there's >1 locker then there's no
room for it in the on-disk tuple header, either.

regards, tom lane

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