| From: | Enrique Sánchez <enriqueesanchz(at)gmail(dot)com> |
|---|---|
| To: | Ilia Evdokimov <ilya(dot)evdokimov(at)tantorlabs(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: | 2026-06-16 22:32:40 |
| Message-ID: | CAOCkzAnpimojq1=+KqdVco37K9v0TiDgC2uQ+QBNfkDcjR0Gqg@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi,
On 15/06/26 23:13, Ilia Evdokimov wrote:
> 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().
>
Makes sense, I've fixed it in v5-0002.
I've also created a commit fest entry for this patch:
https://commitfest.postgresql.org/patch/6898/
Best regards,
Enrique.
| Attachment | Content-Type | Size |
|---|---|---|
| v5-0001-Cap-selectivity-when-values-are-not-in-multi-colu.patch | text/x-patch | 11.4 KB |
| v5-0002-Use-ndistinct-to-cap-non-MCV-values.patch | text/x-patch | 13.4 KB |
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