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Re: URGENET: ALTER statement exectuation hangs when it is executed multiple time on a table

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Dennis Wang <dennis_02_2002(at)hotmail(dot)com>
Cc: Postgresql Help <pgsql-interfaces(at)postgresql(dot)org>
Subject: Re: URGENET: ALTER statement exectuation hangs when it is executed multiple time on a table
Date: 2008-01-11 01:09:58
Message-ID: 20042.1200013798@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-interfaces
Dennis Wang <dennis_02_2002(at)hotmail(dot)com> writes:
>   The actual PostgreSQL commands are:
>      ALTER TABLE warngrid ALTER COLUMN id SET DEFAULT (nextval('warngrid_seq')* 10)+1;
>      COPY warngrid FROM 'warngrid.csv' CSV HEADER; 
>      ALTER TABLE warngrid ALTER COLUMN id DROP DEFAULT;
 
> For the first time, these operation execute fine.  Then I do these steps:
>   4. delete all the records in the table
>   5. rerun the shell script to copy records.
 
> Then, the ALTER statement in step 1 hanging there.

Did you do all this in one database session, or more than one?  If the
latter, maybe you haven't committed the transaction that did the DELETE?

> I did check the lock state of the warngrid table, it says the process created by the ALTER statement hold an "AccessExclusiveLock" on the table. 

Did it actually *have* that lock, or was it waiting for it (granted = f
in pg_locks)?

			regards, tom lane

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