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help / color / mirror / Atom feedFrom: Ron Johnson <[email protected]>
To: [email protected] <[email protected]>
Subject: Re: analyze-in-stages post upgrade questions
Date: Fri, 27 Jun 2025 09:41:39 -0400
Message-ID: <CANzqJaCC8QT8yugqF8vM_5Rs1eiTy9iWbQ=Ty8Bre93u7rh_FQ@mail.gmail.com> (raw)
In-Reply-To: <CO1PR04MB8281387B9AD9DE30976966BBC045A@CO1PR04MB8281.namprd04.prod.outlook.com>
References: <CO1PR04MB8281387B9AD9DE30976966BBC045A@CO1PR04MB8281.namprd04.prod.outlook.com>
On Fri, Jun 27, 2025 at 9:35 AM Zechman, Derek S <[email protected]>
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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Subject: Re: analyze-in-stages post upgrade questions
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