| From: | Ilia Evdokimov <ilya(dot)evdokimov(at)tantorlabs(dot)com> |
|---|---|
| To: | Enrique Sánchez <enriqueesanchz(at)gmail(dot)com> |
| Cc: | Chengpeng Yan <chengpeng_yan(at)outlook(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Zsolt Parragi <zsolt(dot)parragi(at)percona(dot)com> |
| Subject: | Re: Extended statistics improvement: multi-column MCV missing values |
| Date: | 2026-06-15 21:13:42 |
| Message-ID: | 3ccc8ad1-3e84-4d2b-9556-843aded20128@tantorlabs.com |
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| Lists: | pgsql-hackers |
On 6/10/26 03:57, Enrique Sánchez wrote:
> You can check v4-0002.
It's generally not safe to compare floating-point values for equality. I
mean using `mcv_sel == 0.0` to detect that there are no extended MCV
matches. IMO, we should use a bool variable (similar to how
var_eq_const() does it) to track whether any MCV item matched,
specifically in the loop where we check extended MCV matches in
mcv_clauselist_selectivity(), and use that instead of checking `mcv_sel
== 0.0`.
--
Best regards,
Ilia Evdokimov,
Tantor Labs LLC,
https://tantorlabs.com/
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