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From: Dimitrios Apostolou <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: [email protected]
Subject: Re: Experience and feedback on pg_restore --data-only
Date: Mon, 24 Mar 2025 15:24:17 +0100 (CET)
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On Sun, 23 Mar 2025, Laurenz Albe wrote:

> On Thu, 2025-03-20 at 23:48 +0100, Dimitrios Apostolou wrote:
>> Performance issues: (important as my db size is >5TB)
>>
>> * WAL writes: I didn't manage to avoid writing to the WAL, despite having
>>    setting wal_level=minimal. I even wrote my own function to ALTER all
>>    tables to UNLOGGED, but failed with "could not change table T to
>>    unlogged because it references logged table".  I'm out of ideas on this
>>    one.
>
> You'd have to create an load the table in the same transaction, that is,
> you'd have to run pg_restore with --single-transaction.

That would restore the schema from the dump, while I want to create the
schema from the SQL code in version control.

Something that might work, would be for pg_restore to issue a TRUNCATE
before the COPY. I believe this would require superuser privelege though,
that I would prefer to avoid. Currently I issue TRUNCATE for all tables
manually before running pg_restore, but of course this is in a different
transaction so it doesn't help.

By the way do you see potential problems with using --single-transaction
to restore billion-rows tables?


Thank you,
Dimitris

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