Re: adding foreign key constraint locks up table

On Tue, Dec 28, 2010 at 8:55 AM, kakarukeys <kakarukeys(at)gmail(dot)com> wrote:

>
> > How long did you wait?
> hours in the past.
> For recent happenings, I aborted after 10 mins.
>
> Since it's a new table's creation, 'bbb' is empty.
> The 'alter table' never finished, so the lock was not released.
> aaa.id, bbb.topic_id are integers (id is auto-increament key)
>

That surely is a _long_ time for an empty table's ALTER.

>
>
> I also saw this:
>
> http://postgresql.1045698.n5.nabble.com/Update-INSERT-RULE-while-running-for-Partitioning-td2057708.html
>
> "Note that using ALTER TABLE to add a constraint as well as
> using DROP TABLE or TRUNCATE to remove/recycle partitions are
> DDL commands that require exclusive locks. This will block
> both readers and writers to the table(s) and can also cause readers
> and writers to now interfere with each other. "
>
>
In your case ALTER TABLE would lock bbb, but not aaa; other sessions should
still be able to read aaa.

Regards,
--
gurjeet.singh
@ EnterpriseDB - The Enterprise Postgres Company
http://www.EnterpriseDB.com

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