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

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