| From: | Michael Paquier <michael(at)paquier(dot)xyz> |
|---|---|
| To: | Fabrízio de Royes Mello <fabriziomello(at)gmail(dot)com> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Add important info about ANALYZE after create Functional Index |
| Date: | 2020-10-28 05:14:55 |
| Message-ID: | 20201028051455.GH28445@paquier.xyz |
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| Lists: | pgsql-hackers |
On Tue, Oct 27, 2020 at 11:06:22AM -0300, Fabrízio de Royes Mello wrote:
> When we create a new table or index they will not have statistics until an
> ANALYZE happens. This is the default behaviour and I think is not a big
> problem here, but we need to add some note on docs about the need of
> statistics for indexes on expressions.
>
> But IMHO there is a misbehaviour with the implementation of CONCURRENTLY on
> REINDEX because running it will lose the statistics. Have a look the
> example below:
>
> [...]
>
> So IMHO here is the place we should rework a bit to execute ANALYZE as a
> last step.
I agree that this is not user-friendly, and I suspect that we will
need to do something within index_concurrently_swap() to fill in the
stats of the new index from the data of the old one (not looked at
that in details yet).
--
Michael
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