| From: | Andrei Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru> |
|---|---|
| To: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Optimization outcome depends on the index order |
| Date: | 2023-12-22 17:24:37 |
| Message-ID: | 9b3dbf6d-776a-4953-a5a4-60992939321d@postgrespro.ru |
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| Lists: | pgsql-hackers |
On 22/12/2023 11:48, Alexander Korotkov wrote:
> > Because we must trust all predictions made by the planner, we just
> > choose the most trustworthy path. According to the planner logic, it is
> > a path with a smaller selectivity. We can make mistakes anyway just
> > because of the nature of estimation.
>
> Even if we need to take selectivity into account here, it's still not
> clear why this should be on top of other logic later in add_path().
I got your point now, thanks for pointing it out. In the next version of
the patch selectivity is used as a criteria only in the case of COSTS_EQUAL.
--
regards,
Andrei Lepikhov
Postgres Professional
| Attachment | Content-Type | Size |
|---|---|---|
| v4-0001-Choose-an-index-path-with-the-best-selectivity-estim.patch | text/plain | 5.7 KB |
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