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help / color / mirror / Atom feedFrom: Isaac Morland <[email protected]>
To: PostgreSQL Hackers <[email protected]>
Subject: Disk space not released after schema deletion
Date: Wed, 7 Jun 2023 11:48:32 -0400
Message-ID: <CAMsGm5f47KVmYZBVKjOKYxtu2iWG9NUOQQFXjS2G1JY6xruiJA@mail.gmail.com> (raw)
The usual question is “why did DELETE not release disk space?”, and I
understand why that is and something about how to get the space back
(VACUUM).
I have a database which hosts multiple applications in various schemas and
I’m trying to make test/sample data files by starting with a restored copy
of production and then dropping all schemas except for the ones I need for
a particular application.
The total size of all relations after the drop operations is just a few MB:
odyssey=# select sum (pg_total_relation_size (oid)) from pg_class;
sum
----------
13877248
(1 row)
Yet the database size is still large (although much smaller than in the
original database):
odyssey=# select datname, pg_database_size (oid) from pg_database;
datname | pg_database_size
-----------+------------------
postgres | 8930083
_repmgr | 654934531
template0 | 8643075
template1 | 8864547
odyssey | 14375453475
(5 rows)
The only change made after starting from a basebackup of production was to
set all the passwords to NULL in pg_authid, and to delete most of the
schemas. In particular, I wouldn’t expect VACUUM to do anything.
Does anybody know what could be holding all that space?
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Subject: Re: Disk space not released after schema deletion
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