Date: Thu, 25 Aug 2022 14:44:11 +0200
From: hubert depesz lubaczewski <depesz@depesz.com>
Sender: depesz@depesz.com
To: PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: pg_restore deadlocks with itself
Message-ID: <20220825124411.GA8257@depesz.com>
Reply-To: depesz@depesz.com
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
User-Agent: Mutt/1.10.1 (2018-07-13)
Archived-At: 
 <https://www.postgresql.org/message-id/20220825124411.GA8257%40depesz.com>
Precedence: bulk

Hi,
I have Pg 14.4 on arm64, and I'm loading schema dump from pg12.

Specifically, command to run it is:
sudo -u postgres pg_restore -j 64 -d database -L /tmp/schema-post-data.nopkey.list /tmp/schema-post-data.dump

where /tmp/schema-post-data.dump is dump made using:
sudo -u postgres pg_dump --schema-only --compress=9 --format=c --section='post-data' --schema='*(something|else|xxx)*' database

and /tmp/schema-post-data.nopkey.list is made using:

#v+
pkey_regexp='^\d+; \d+ \d+ CONSTRAINT \S+ \S+ \S+_pkey '
pg_restore -l "${local_dump_dir}/schema-post-data.dump" | grep -vP "${pkey_regexp}" > "${local_dump_dir}/schema-post-data.nopkey.list"
#v-

The thing is that the list file has 7676 lines, out of which 2313 are
foreign keys.

database has basically 3 schemas, and fkeys NEVER cross schema.

When loading the dump I got reported 4 errors, but log shows 2 deadlocks.
perhaps all sides got cancelled, not sure, will investigate further, but logs
show:

2022-08-24 20:01:04.466 UTC,"postgres","database",3343477,"[local]",630624ad.330475,42,"ALTER TABLE waiting",2022-08-24 13:16:29 UTC,21/1932,0,LOG,00000,"process 3343477 detected deadlock while waiting for ShareRowExclusiveLock on relation 742617610 of database 16641 after 1000.647 ms","Process holding the lock: 3587718. Wait queue: .",,,,,"ALTER TABLE ONLY some_schema.table_a_o
    ADD CONSTRAINT table_a_o_q_id_fk FOREIGN KEY (q_id) REFERENCES some_schema.table_q(id);
",,,"pg_restore","client backend",,3355460102417501954


2022-08-24 20:01:50.291 UTC,"postgres","database",3343477,"[local]",630624ad.330475,46,"ALTER TABLE waiting",2022-08-24 13:16:29 UTC,21/1933,0,LOG,00000,"process 3343477 detected deadlock while waiting for ShareRowExclusiveLock on relation 742617610 of database 16641 after 1000.030 ms","Process holding the lock: 3587718. Wait queue: .",,,,,"ALTER TABLE ONLY some_schema.table_a
    ADD CONSTRAINT fk_rails_46718e626a FOREIGN KEY (migrate_from_id) REFERENCES some_schema.table_q(id);
",,,"pg_restore","client backend",,-2548896815899838768

Now, I know I can fix the situation by adding missing fkeys myself, but
I don't think pg_restore should be putting itself in deadlock.

Best regards,

depesz