Horton

Re: [HACKERS] PATCH: multivariate histograms and MCV lists

Dean Rasheed <dean.a.rasheed@gmail.com>

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From: Dean Rasheed <dean.a.rasheed@gmail.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, Thomas Munro <thomas.munro@enterprisedb.com>, Mark Dilger <hornschnorter@gmail.com>, Adrien Nayrat <adrien.nayrat@dalibo.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-04-07T17:52:42Z
Lists: pgsql-hackers 
On 7 April 2018 at 15:12, Bruce Momjian <bruce@momjian.us> wrote:
> Uh, where are we on this patch?  It isn't going to make it into PG 11?
> Feature development for this has been going on for years.

Unfortunately, I think there's no way that this will be ready for
PG11. So far, I have only read parts of the patch, focusing mainly on
the planner changes, and how it will make use of the new statistics. I
think there are still issues to work out in that area, although I
haven't read the latest version yet, I have some doubts about the new
approach described.

Looking back at the history of this patch, it appears to have moved
through all 4 PG11 commitfests with fairly minimal review, never
becoming Ready for Committer. That's a real shame because I agree that
it's an important feature, but IMO it's not yet in a committable
state. I feel bad saying that, because the patch hasn't really had a
fair chance to-date, despite Tomas' efforts and quick responses to all
review comments.

At this stage though, all I can say is that I'll make every effort to
keep reviewing it, and I hope Tomas will persist, so that it has a
better chance in PG12.

Regards,
Dean

Commits

  1. Convert pre-existing stats_ext tests to new style

  2. Add support for multivariate MCV lists

  3. Improve ANALYZE's strategy for finding MCVs.

  4. Clone extended stats in CREATE TABLE (LIKE INCLUDING ALL)

  5. Try again to fix accumulation of parallel worker instrumentation.

  6. Adjust psql \d query to avoid use of @> operator.

  7. Message style fixes

  8. Add security checks to selectivity estimation functions