Re: AccessShareLock question

[Clayton Graf <clayton.graf@xxxxxxxxx>]

Ok, but this is really my problem: I cannot perform an ALTER TABLE with the system in production mode, because the ALTER TABLE hangs due an AccessShareLock.

We use two-tier mode, so is it necessary to shutdown all users before perform an ALTER TABLE? Is it this true? 

Thanks,

Clayton

2009/12/19 Jaime Casanova <jcasanov@xxxxxxxxxxxxxxxxxxx>

On Sat, Dec 19, 2009 at 9:04 AM, Clayton Graf <clayton.graf@xxxxxxxxx> wrote:
> I get an AccessShareLock in a simple select command and I am not using the
> FOR SHARE clause.

http://www.postgresql.org/docs/current/static/explicit-locking.html says:
"""
ACCESS SHARE

   Conflicts with the ACCESS EXCLUSIVE lock mode only.

   The SELECT command acquires a lock of this mode on referenced
tables. In general, any query that only reads a table and does not
modify it will acquire this lock mode.
"""
in other words, everything is ok, AccessShareLock doesn't block
anything but with anyone trying to change the structure of the table
(ALTER, DROP) and with commands TRUNCATE, REINDEX, CLUSTER, and VACUUM
FULL, and every select take it

--
Atentamente,
Jaime Casanova
Soporte y capacitación de PostgreSQL
Asesoría y desarrollo de sistemas
Guayaquil - Ecuador
Cel. +59387171157

-- 
Clayton Graf