| From: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
|---|---|
| To: | Christopher Jackson <crjackso(at)gmail(dot)com> |
| Cc: | bricklen <bricklen(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org list" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Slow Count-Distinct Query |
| Date: | 2014-04-02 04:48:12 |
| Message-ID: | CAB7nPqQaN3S+RBk2EhL7KCWdkYO4zsri_bb1n5y8fCB_6urPqQ@mail.gmail.com |
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| Lists: | pgsql-performance |
On Wed, Apr 2, 2014 at 1:22 PM, Christopher Jackson <crjackso(at)gmail(dot)com> wrote:
>
> Hi Bricklen,
>
> Thanks for the feedback. I'll play around with materialized views. My
> understanding is they have to be manually triggered for refresh
Yep.
> and there's an exclusive lock on the view while the refresh is taking place. Is this
> your understanding as well?
Re-yep.
> I'm using PG 9.3.3. If this is true, I'm
> curious what clever ways people have come up with to mitigate any issues
> with the lock.
Kevin Grittner has implemented REFRESH MATERIALIZED VIEW CONCURRENTLY
in 9.4. A unique index is needed on the materialized view as well to
authorize this concurrent operation. It has the merit to allow SELECT
operations on the matview during the refresh.
--
Michael
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