Re: Postgres for a "data warehouse", 5-10 TB

On Tue, Sep 13, 2011 at 19:34, Robert Klemme <shortcutter(at)googlemail(dot)com> wrote:
> I don't think so.  You only need to catch the error (see attachment).
> Or does this create a sub transaction?

Yes, every BEGIN/EXCEPTION block creates a subtransaction -- like a
SAVEPOINT it can roll back to in case of an error.

> Yes, I mentioned the speed issue.  But regardless of the solution for
> MySQL's "INSERT..ON DUPLICATE KEY UPDATE" which Igor mentioned you
> will have the locking problem anyhow if you plan to insert
> concurrently into the same table and be robust.

In a mass-loading application you can often divide the work between
threads in a manner that doesn't cause conflicts.

For example, if the unique key is foobar_id and you have 4 threads,
thread 0 will handle rows where (foobar_id%4)=0, thread 1 takes
(foobar_id%4)=1 etc. Or potentially hash foobar_id before dividing the
work.

I already suggested this in my original post.

Regards,
Marti