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From: David Rowley <david.rowley@2ndquadrant.com>
Date: Mon, 13 May 2019 14:19:45 +1200
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Subject: Re: PostgreSQL 12: Feature Highlights
To: Justin Clift <justin@postgresql.org>
Cc: "Jonathan S. Katz" <jkatz@postgresql.org>,
 pgsql-advocacy@lists.postgresql.org
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On Mon, 13 May 2019 at 13:50, Justin Clift <justin@postgresql.org> wrote:
>
> On 2019-05-13 09:47, David Rowley wrote:
> > On Mon, 13 May 2019 at 03:28, Jonathan S. Katz <jkatz@postgresql.org>
> > wrote:
> >> - Performance, e.g. enhanced partition pruning, COPY performance,
> >> ATTACH
> >
> > I don't think it's very accurate to say that the performance of
> > partition pruning has been improved. Really the improvement there is
> > due to the change in the order of operations, where we now perform
> > pruning before fetching partition meta-data. Pruning itself, I don't
> > believe became any faster in PG12. There were, however various tweaks
> > to improve performance of some operations around run-time partition
> > pruning both in the planner and during execution, these, however, are
> > not improvements to pruning itself, but more the operations around
> > setting up pruning and handling what happens after pruning takes
> > place. Bruce has now changed the release notes to mention "Improve
> > performance of many operations on partitioned tables", which seems
> > like a more accurate generalisation of what was improved, although, I
> > still think it's overly vague.
>
> Sounds like "partition pruning is now more efficient".  eg less memory
> usage (?), with a side effect of better performance leading from that
> (?)

I think the headline item needs to be about the fact that partitioning
can now more easily handle larger numbers of partitions. To say
pruning is more efficient is just a chapter in the story. The big
users of partitioning want and need the entire book.

Perhaps something along the lines of:

- Improve optimizer and executor to allow them to more easily handle
larger numbers of partitions.
- Allow ATTACH PARTITION to work without blocking concurrent DML.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services