From: PG Bug reporting form <noreply@postgresql.org>
To: pgsql-bugs@lists.postgresql.org
Cc: mhararci@gmail.com
Subject: BUG #19051: Is it possible to move a TOAST table to a different tablespace than its parent table?
Date: Sun, 14 Sep 2025 09:17:05 +0000
Message-ID: <19051-90b4476ef19f9b73@postgresql.org> (raw)
The following bug has been logged on the website:
Bug reference: 19051
Logged by: Mustafa HARARCI
Email address: mhararci@gmail.com
PostgreSQL version: 16.10
Operating system: Ubuntu 16.10-1.pgdg22.04+1
Description:
Hello everyone,
I'm currently using PostgreSQL 16.10 and I've run into a challenge regarding
moving TOAST data for a table. My goal is to have the TOAST data for a
column stored in a different tablespace from the parent table.
Specifically, I have a users table with a profile_data column of type JSONB,
which can contain large objects. I want the users table itself to reside in
the ts_medium_data tablespace, while its associated TOAST data is stored in
a separate ts_medium_toast tablespace.
I've attempted the following steps:
I created the users table in the ts_medium_data tablespace.
I identified the associated TOAST table using the pg_class catalog (SELECT
reltoastrelid::regclass FROM pg_class WHERE relname = 'users';), which
returned an object like pg_toast.pg_toast_16646.
As a superuser (postgres), I tried to move the TOAST table to the new
tablespace using ALTER TABLE pg_toast.pg_toast_16646 SET TABLESPACE
ts_medium_toast;.
This command, however, resulted in the following error: ERROR: permission
denied: "pg_toast_16646" is a system catalog.
This error suggests that direct modification of the TOAST table is not
allowed, even with superuser privileges.
My question is, is it fundamentally possible in PostgreSQL to store a
table's main data and its TOAST data in different tablespaces? Is this
behavior a design constraint? If so, is there any workaround for this, or is
this simply not a supported feature?
Any insight into this behavior or guidance on a potential solution would be
greatly appreciated.
Thank you.
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Subject: Re: BUG #19051: Is it possible to move a TOAST table to a different tablespace than its parent table?
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