| From: | Ron Johnson <ronljohnsonjr(at)gmail(dot)com> |
|---|---|
| To: | "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: analyze-in-stages post upgrade questions |
| Date: | 2025-06-27 13:41:39 |
| Message-ID: | CANzqJaCC8QT8yugqF8vM_5Rs1eiTy9iWbQ=Ty8Bre93u7rh_FQ@mail.gmail.com |
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| Lists: | pgsql-general |
On Fri, Jun 27, 2025 at 9:35 AM Zechman, Derek S <Derek(dot)S(dot)Zechman(at)snapon(dot)com>
wrote:
>
>
> We recently performed an upgrade from pg14 (14.18) to pg16 (16.9) and
> performed the analyze-in-stages post upgrade. It has been noticed that
> some plans changed to use hash joins instead of nested loops. Further
> investigation found it was because the parent table of partitioned tables
> did not have stats. After running an ANALYZE on the parent tables we got
> similar plan an execution times as before.
>
>
>
> I have two questions
>
> 1 - Why does analyze-in-stages not analyze the parent tables?
>
> 2 – What happens if we do not run analyze-in-stages post upgrade and just
> run an analyze?
>
It takes more time, and you don't have *any* statistics on a given table
until the ANALYZE on that table completes.
How long did "vacuumdb --analyze-only --jobs=$mumble your_db" take?
--
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!
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