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From: Riku Iki <[email protected]>
To: [email protected]
Subject: Preallocation changes in Postgresql 16
Date: Wed, 24 Apr 2024 18:44:47 -0700
Message-ID: <CAMazQQfp+3f8tD_Q23rCR=O+Jj4jouSRVigbD8OmrTOfHV+8gA@mail.gmail.com> (raw)

Hi,

We have PostgreSQL server, which currently runs PostgreSQL 15 on compressed
btrfs.

I tried to migrate DB to PostgreSQL 16, and found that data is not being
compressed for PostgreSQL 16 server. One of the possible reason why btrfs
won't compress data is data preallocation.

When running "compsize" tool, I indeed see that PostgreSQL preallocating
data and it is not compressed (there is separate "preallocated" entry in
output).

I am wondering if there were preallocation related changes in PG16, and if
it is possible to disable preallocation in PostgreSQL 16?

I posted
<https://dba.stackexchange.com/questions/338906/preallocation-changes-in-postgresql-16;
this on StackExchange, and someone pointed on this commit
<https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=00d1e02be24987180115e371abaeb84738257...;
as possible reason of such behavior.

Long discussion
<https://lore.kernel.org/all/[email protected]/T/;
on
lore.kernel.org about exactly this issue.

reply

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