PostgreSQL 12: Feature Highlights

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Re: PostgreSQL 12: Feature Highlights

Bruce Momjian
On Wed, May 22, 2019 at 12:33:10PM +1200, David Rowley wrote:

> On Wed, 22 May 2019 at 02:55, Bruce Momjian <[hidden email]> wrote:
> > This brings up a few points.  First, it seems the change affects
> > partitioned tables and UNION ALL, which means it probably needs to be
> > listed in two sections.   Second, is it only parallelism paths that are
> > added?  I am not sure if people care about a node being removed,
> > especially when the might not even know we do that step, but they do
> > care if there are new optimization possibilities.
>
> Like Amit, I think the optimizer section is fine.  Another thing that
> is affected is that you may no longer get a Materialize node in the
> plan.  Previously you might have gotten something like Merge Join ->
> Materialize -> Append -> Seq Scan, now you might just get Merge Join
> -> Seq Scan.  This is because Append / MergeAppend don't support mark
> and restore. Removing them would allow the materialize node to be
> skipped in cases where the single subpath of the Append does support
> mark and restore.
How is this patch for the item?  I put it in the Optimizer section.

--
  Bruce Momjian  <[hidden email]>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +

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Re: PostgreSQL 12: Feature Highlights

David Rowley-3
On Fri, 14 Jun 2019 at 15:24, Bruce Momjian <[hidden email]> wrote:

>
> On Wed, May 22, 2019 at 12:33:10PM +1200, David Rowley wrote:
> > On Wed, 22 May 2019 at 02:55, Bruce Momjian <[hidden email]> wrote:
> > > This brings up a few points.  First, it seems the change affects
> > > partitioned tables and UNION ALL, which means it probably needs to be
> > > listed in two sections.   Second, is it only parallelism paths that are
> > > added?  I am not sure if people care about a node being removed,
> > > especially when the might not even know we do that step, but they do
> > > care if there are new optimization possibilities.
> >
> > Like Amit, I think the optimizer section is fine.  Another thing that
> > is affected is that you may no longer get a Materialize node in the
> > plan.  Previously you might have gotten something like Merge Join ->
> > Materialize -> Append -> Seq Scan, now you might just get Merge Join
> > -> Seq Scan.  This is because Append / MergeAppend don't support mark
> > and restore. Removing them would allow the materialize node to be
> > skipped in cases where the single subpath of the Append does support
> > mark and restore.
>
> How is this patch for the item?  I put it in the Optimizer section.

That looks fine. Thank you.

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


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Re: PostgreSQL 12: Feature Highlights

Bruce Momjian
On Fri, Jun 14, 2019 at 03:57:45PM +1200, David Rowley wrote:

> On Fri, 14 Jun 2019 at 15:24, Bruce Momjian <[hidden email]> wrote:
> >
> > On Wed, May 22, 2019 at 12:33:10PM +1200, David Rowley wrote:
> > > On Wed, 22 May 2019 at 02:55, Bruce Momjian <[hidden email]> wrote:
> > > > This brings up a few points.  First, it seems the change affects
> > > > partitioned tables and UNION ALL, which means it probably needs to be
> > > > listed in two sections.   Second, is it only parallelism paths that are
> > > > added?  I am not sure if people care about a node being removed,
> > > > especially when the might not even know we do that step, but they do
> > > > care if there are new optimization possibilities.
> > >
> > > Like Amit, I think the optimizer section is fine.  Another thing that
> > > is affected is that you may no longer get a Materialize node in the
> > > plan.  Previously you might have gotten something like Merge Join ->
> > > Materialize -> Append -> Seq Scan, now you might just get Merge Join
> > > -> Seq Scan.  This is because Append / MergeAppend don't support mark
> > > and restore. Removing them would allow the materialize node to be
> > > skipped in cases where the single subpath of the Append does support
> > > mark and restore.
> >
> > How is this patch for the item?  I put it in the Optimizer section.
>
> That looks fine. Thank you.

Done, thanks.

--
  Bruce Momjian  <[hidden email]>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +


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