Horton

Re: Additional improvements to extended statistics

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

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From: Dean Rasheed <dean.a.rasheed@gmail.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-03-13T16:54:51Z
Lists: pgsql-hackers 
On Mon, 9 Mar 2020 at 00:06, Tomas Vondra <tomas.vondra@2ndquadrant.com> wrote:
>
> On Mon, Mar 09, 2020 at 01:01:57AM +0100, Tomas Vondra wrote:
> >
> >Attaches is an updated patch series
> >with parts 0002 and 0003 adding tests demonstrating the issue and then
> >fixing it (both shall be merged to 0001).
> >
>
> One day I won't forget to actually attach the files ...
>

0001-0003 look reasonable to me.

One minor point -- there are now 2 code blocks that are basically the
same, looping over a list of clauses, calling clause_selectivity() and
then applying the "s1 = s1 + s2 - s1 * s2" formula. Perhaps they could
be combined into a new function (clauselist_selectivity_simple_or(),
say). I guess it would need to be passed the initial starting
selectivity s1, but it ought to help reduce code duplication.

Regards,
Dean

Commits

  1. Improve estimation of ANDs under ORs using extended statistics.

  2. Improve estimation of OR clauses using multiple extended statistics.

  3. Improve estimation of OR clauses using extended statistics.

  4. Prevent functional dependency estimates from exceeding column estimates.

  5. Fix wording of several extended stats comments

  6. Improve test coverage for multi-column MCV lists

  7. Improve test coverage for functional dependencies