| From: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
|---|---|
| To: | Jian Guo <gjian(at)vmware(dot)com>, Hans Buschmann <buschmann(at)nidsa(dot)net>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Cc: | Zhenghua Lyu <zlyu(at)vmware(dot)com> |
| Subject: | Re: Wrong rows estimations with joins of CTEs slows queries by more than factor 500 |
| Date: | 2023-08-21 10:56:18 |
| Message-ID: | 8e629488-cb14-5f17-adb3-c02205ebacab@enterprisedb.com |
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| Lists: | pgsql-hackers |
On 8/21/23 10:16, Jian Guo wrote:
> Hi hackers,
>
> I found a new approach to fix this issue, which seems better, so I would
> like to post another version of the patch here. The origin patch made
> the assumption of the values of Vars from CTE must be unique, which
> could be very wrong. This patch examines variables for Vars inside CTE,
> which avoided the bad assumption, so the results could be much more
> accurate.
>
No problem with posting a reworked patch to the same thread, but I'll
repeat my suggestion to register this in the CF app [1]. The benefit is
that people are more likely to notice the patch and also cfbot [2] will
run regression tests.
[1] https://commitfest.postgresql.org
[2] http://cfbot.cputube.org/
--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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