From: Atesz <atesz@ritek.hu>
To: pgsql-performance@postgresql.org
Subject: ACCESS EXCLUSIVE lock
Date: Wed, 18 Oct 2006 16:24:30 +0200
Message-ID: <4536391E.7040604@ritek.hu> (raw)
Hi!
I have a problem with ACCESS EXCLUSIVE lock when I drop a reference in
transaction. I have 2 tables:
create table a(id SERIAL primary key);
create table b(id SERIAL primary key references a(id));
After that I have 2 processes: P1, P2
In P1:
begin;
ALTER TABLE b DROP CONSTRAINT b_id_fkey;
In P2:
SELECT * FROM a;
And I'm waiting for the result, but I don't get until P1 finishes.
I know the DROP CONSTRAINT put an ACCESS EXCLUSIVE table LOCK into the
TABLE a, and the SELECT is stopped by this LOCK in P2.
Note: I cannot commit the P1 earlier, because it's a very long
transaction (more hours, data conversion transaction)
My question: Why need this strict locking?
In my opinion there isn't exclusion between the DROP CONSTRAINT and the
SELECT.
Thanks for your suggestions!
Regards,
Antal Attila
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: atesz@ritek.hu
Subject: Re: ACCESS EXCLUSIVE lock
In-Reply-To: <4536391E.7040604@ritek.hu>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox