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

Dennis Wang <dennis_02_2002@hotmail.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