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From: Nathan Bossart <[email protected]>
To: Tom Lane <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Corey Huinker <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Jeff Davis <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: jian he <[email protected]>
Cc: Bruce Momjian <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: Magnus Hagander <[email protected]>
Cc: Stephen Frost <[email protected]>
Cc: Ashutosh Bapat <[email protected]>
Cc: Peter Smith <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: [email protected]
Subject: Re: Statistics Import and Export
Date: Thu, 6 Mar 2025 13:33:13 -0600
Message-ID: <Z8n4eUTS_iEq3mxn@nathan> (raw)
In-Reply-To: <[email protected]>
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	<[email protected]>

On Thu, Mar 06, 2025 at 01:47:34PM -0500, Tom Lane wrote:
> 1. pg_upgrade has made a policy judgement to apply parallelism across
> databases not within a database, ie it will launch concurrent dump/
> restore tasks in different DBs but not authorize any one of them to
> eat multiple CPUs.  That needs to be re-thought probably, as I think
> that decision dates to before we had useful parallelism in pg_dump and
> pg_restore.  I wonder if we could just rip out pg_upgrade's support
> for DB-level parallelism, which is not terribly pretty anyway, and
> simply pass the -j switch straight to pg_dump and pg_restore.

That would certainly help for clusters with one big database with many LOs
or something, but I worry it would hurt the many database case quite a bit.
Maybe we could add a --jobs-per-db option that indicates how to parallelize
dump/restore.  If you set --jobs=8 --jobs-per-db=8, the databases would be
dumped serially, but pg_dump would get -j8.  If you set --jobs=8 and
--jobs-per-db=2, we'd process 4 databases at a time, each with -j2.

-- 
nathan






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  Subject: Re: Statistics Import and Export
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