Re: Slow Count-Distinct Query - Mailing list pgsql-performance

From Michael Paquier
Subject Re: Slow Count-Distinct Query
Date
Msg-id CAB7nPqQaN3S+RBk2EhL7KCWdkYO4zsri_bb1n5y8fCB_6urPqQ@mail.gmail.com
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In response to Re: Slow Count-Distinct Query  (Christopher Jackson <crjackso@gmail.com>)
Responses Re: Slow Count-Distinct Query
List pgsql-performance
On Wed, Apr 2, 2014 at 1:22 PM, Christopher Jackson <crjackso@gmail.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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