| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | "Shulgin, Oleksandr" <oleksandr(dot)shulgin(at)zalando(dot)de> |
| Cc: | David Steele <david(at)pgmasters(dot)net>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: More stable query plans via more predictable column statistics |
| Date: | 2016-03-08 19:16:01 |
| Message-ID: | 20160308191601.GA907936@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Shulgin, Oleksandr wrote:
> Alright. I'm attaching the latest version of this patch split in two
> parts: the first one is NULLs-related bugfix and the second is the
> "improvement" part, which applies on top of the first one.
I went over patch 0001 and it seems pretty reasonable. It's missing
some comment updates -- at least the large comments that talk about Duj1
should be modified to indicate why the code is now subtracting the null
count. Also, I can't quite figure out why the "else" now in line 2131
is now "else if track_cnt != 0". What happens if track_cnt is zero?
The comment above the "if" block doesn't provide any guidance.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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