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From: David Rowley <[email protected]>
To: Justin Clift <[email protected]>
Cc: Jonathan S. Katz <[email protected]>
Cc: [email protected]
Subject: Re: PostgreSQL 12: Feature Highlights
Date: Mon, 13 May 2019 14:19:45 +1200
Message-ID: <CAKJS1f9=xUz5y=VDy6hYMVpSoej9+D2BminegmfqHwdWQfpQ9w@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<CAKJS1f-1=BoVkJaTnfb87nrVUFLprdc7smsBsF5MGyCXnNivzw@mail.gmail.com>
	<[email protected]>

On Mon, 13 May 2019 at 13:50, Justin Clift <[email protected]> wrote:
>
> On 2019-05-13 09:47, David Rowley wrote:
> > On Mon, 13 May 2019 at 03:28, Jonathan S. Katz <[email protected]>
> > 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

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