Обсуждение: pg_dump -Are statistics saved?

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pg_dump -Are statistics saved?

От
Murthy Nunna
Дата:

Hello,

 

We are running pg version 14.4

 

I did a pg_dump of a fairly large database (~20TB). I plan to pg_restore it on same server after upgrading Linux from Scientific Linux release 7.9 to Alma 9. We are forced to do pg_dump/pg_restore due to glibc collation changes in Alma 9.

 

The pg_dump (used verbose) log said “pg_dump: reading extended statistics”.

 

Does it mean it saved statistics and they can be restored with pg_restore? If not, is it necessary to run ANALYZE after pg_restore?

 

Thanks in advance for responding.

 

Re: pg_dump -Are statistics saved?

От
"David G. Johnston"
Дата:
On Mon, Nov 27, 2023 at 5:28 PM Murthy Nunna <mnunna@fnal.gov> wrote:

Does it mean it saved statistics and they can be restored with pg_restore? If not, is it necessary to run ANALYZE after pg_restore?

 


Logical dumps do not output system catalogs except large objects.  It outputs object definitions In SQL form.  Though I'm unsure of that specific message.

David J.

Re: pg_dump -Are statistics saved?

От
Tom Lane
Дата:
Murthy Nunna <mnunna@fnal.gov> writes:
> The pg_dump (used verbose) log said "pg_dump: reading extended statistics".

> Does it mean it saved statistics and they can be restored with pg_restore?

What that means is that it will output clones of any CREATE STATISTICS
commands you may have issued.

> If not, is it necessary to run ANALYZE after pg_restore?

That has always been necessary after a dump/restore, and still is.
The pg_dump man page makes this clear enough, I should think:

    The dump file produced by pg_dump does not contain the statistics used
    by the optimizer to make query planning decisions. Therefore, it is
    wise to run ANALYZE after restoring from a dump file to ensure optimal
    performance; see Section 25.1.3 and Section 25.1.6 for more
    information.

            regards, tom lane

Re: pg_dump -Are statistics saved?

От
Laurenz Albe
Дата:
On Mon, 2023-11-27 at 19:45 -0500, Tom Lane wrote:
> Murthy Nunna <mnunna@fnal.gov> writes:
>
>
> > If not, is it necessary to run ANALYZE after pg_restore?
>
> That has always been necessary after a dump/restore, and still is.
> The pg_dump man page makes this clear enough, I should think:
>
>     The dump file produced by pg_dump does not contain the statistics used
>     by the optimizer to make query planning decisions. Therefore, it is
>     wise to run ANALYZE after restoring from a dump file to ensure optimal
>     performance; see Section 25.1.3 and Section 25.1.6 for more
>     information.

If you are not pressed for time, you can wait until autovacuum gets around
to calculating the statistics automatically.

Yours,
Laurenz Albe