Horton

Re: Additional improvements to extended statistics

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-03-14T16:56:10Z
Lists: pgsql-hackers

Attachments

On Fri, Mar 13, 2020 at 04:54:51PM +0000, Dean Rasheed wrote:
>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.
>

Attached is a patch series rebased on top of the current master, after
committing the ScalarArrayOpExpr enhancements. I've updated the OR patch
to get rid of the code duplication, and barring objections I'll get it
committed shortly together with the two parts improving test coverage.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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