From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
---|---|
To: | John Lumby <johnlumby(at)hotmail(dot)com> |
Cc: | pgsql general <pgsql-general(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Subject: | Re: REINDEX : new parameter to preserve current average leaf density as new implicit FILLFACTOR |
Date: | 2019-06-26 16:09:08 |
Message-ID: | CAH2-WzkrwRfdw82Se7SdUBivuVy9-o7zByq=p5=ZKSdz=tVdcw@mail.gmail.com |
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Lists: | pgsql-general |
On Wed, Jun 26, 2019 at 8:05 AM John Lumby <johnlumby(at)hotmail(dot)com> wrote:
> > There is a very recent research paper that discusses the idea of
> > varying fillfactor with a view to ameliorating page splits:
> >
>
> Thanks, I am chewing my way through that. As you say, it does address exactly the issues I raised.
> Do you happen to know if their source-code is available somewhere?
> ( I did see their db is MS SQL Server but it still might provide some portable ideas. )
It's just a research paper. It might never be implemented in any system.
The point of the paper is to make page splits occur at a steady rate
after REINDEX'ing -- not to eliminate or even reduce page splits.
> > I suspect that you might find that the enhancements to B-Tree indexes
> > that went into Postgres 12 would help with this workload, especially
> > if you notice that this happens with indexes that have a lot of duplicates
> >
>
> I had not noticed that, thanks for pointing it out. Yes , in my workload most of the indexes in question are non-unique and some have very low key card. I will try out the pg-12 beta when I get a chance.
It's easy to show problems with very low cardinality indexes in the
old code. You'll definitely notice a difference there.
> Is there a pdf or text version?
Just the talk slides:
https://www.pgcon.org/2019/schedule/attachments/518_nbtree-arch-pgcon.pdf
--
Peter Geoghegan
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