Re: How to speed up Exclusive Locking

From: Bernd Helmle <mailings(at)oopsware(dot)de>
To: David Goodenough <david(dot)goodenough(at)btconnect(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: How to speed up Exclusive Locking
Date: 2006-12-05 10:57:39
Message-ID: 378dea27826636cae6e28ff7ef9cce80@oopsware.de
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On Tue, 5 Dec 2006 10:18:21 +0000, David Goodenough <david(dot)goodenough(at)btconnect(dot)com> wrote:

[...]

> The first bits of the sync are done without locking the source tables, and
> I do these until I find less than some suitable threshold of records
> needing
> to be updated. Then I lock the source tables and do the final sync.
>
> The statements issued to lock each table is:-
> LOCK TABLE table IN EXCLUSIVE MODE; SELECT 1 FROM table;
>

So why selecting '1' for each row after locking the relation before? I don't
know HA-JDBC but this looks really useless. Remove the SELECT and use
the LOCK TABLE command within the transaction which does the sync for you.

Bernd

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