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From: Tom Lane <[email protected]>
To: Robert Haas <[email protected]>
Cc: Peter Geoghegan <[email protected]>
Cc: [email protected]
Cc: Andrew <[email protected]>
Subject: Re: pg_dump versus hash partitioning
Date: Wed, 01 Feb 2023 17:33:16 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+TgmoYJ+3XpW_iYapXN3gwq2MECi7GH8BxuwKFCQPOzLaa3OQ@mail.gmail.com>
References: <[email protected]>
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	<CA+TgmoYoSoX8bN_yzabmRDQBNxEaWmjBKPnkZPMUDpPTBy=d4A@mail.gmail.com>
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	<CA+TgmoYJ+3XpW_iYapXN3gwq2MECi7GH8BxuwKFCQPOzLaa3OQ@mail.gmail.com>

Robert Haas <[email protected]> writes:
> Tom, as I understand it, is arguing that the
> --load-via-partition-root behavior has negligible downsides and is
> almost categorically better than the current default behavior, and
> thus making that the new default in some or all situations in a minor
> release is totally fine.

I think it's categorically better than a failed restore.  I wouldn't
be proposing this if there were no such problem; but there is,
and I don't buy your apparent position that we should leave affected
users to cope as best they can.  Yes, it's clearly only a minority
of users that are affected, else we'd have heard complaints before.
But it could be absolutely catastrophic for an affected user,
if they're trying to restore their only backup.  I'd rather impose
an across-the-board cost on all users of hash partitioning than
risk such outcomes for a few.

Also, you've really offered no evidence for your apparent position
that --load-via-partition-root has unacceptable overhead.  We've
done enough work on partition routing over the last few years that
whatever measurements might've originally justified that idea
don't necessarily apply anymore.  Admittedly, I've not measured
it either.  But we don't tell people to avoid partitioning because
INSERT is unduly expensive.  Partition routing is just the cost of
doing business in that space.

			regards, tom lane

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