error during upgrade to 2.2.1

[fvannee]

Relevant system information:

• OS: CentOS
• PostgreSQL version (output of postgres --version): 12
• TimescaleDB version (output of \dx in psql): 1.7.3 -> 2.2.1 upgrade
• Installation method: source

Describe the bug
When upgrading timescaledb, I ran into the following error:

db=# alter extension timescaledb update;
ERROR:  duplicate key value violates unique constraint "saved_privs_tmpnsp_tmpname_key"
DETAIL:  Key (tmpnsp, tmpname)=(_timescaledb_catalog, chunk_constraint_name) already exists.

During the pre-upgrade phase, TSDB saves the pg_init_privs temporarily into a table, with the following SQL.

-- Table for ACL and initprivs of tables. 
CREATE TABLE saved_privs(
       tmpnsp name,
       tmpname name,
       tmpacl aclitem[],
       tmpini aclitem[],
       UNIQUE (tmpnsp, tmpname));

-- We save away both the ACL and the initprivs for all tables and
-- views in the extension (but not for chunks and internal objects) so
-- that we can restore them to the proper state after the update.
INSERT INTO saved_privs
SELECT nspname, relname, relacl, initprivs
  FROM pg_class cl JOIN pg_namespace ns ON ns.oid = relnamespace
                   JOIN pg_init_privs ip ON ip.objoid = cl.oid
WHERE nspname IN ('_timescaledb_catalog', '_timescaledb_config')
   OR nspname = '_timescaledb_internal'
  AND relname IN ('hypertable_chunk_local_size', 'compressed_chunk_stats',
                  'bgw_job_stat', 'bgw_policy_chunk_stats');

The UNIQUE constraint of this table was validated. Indeed, when looking into the catalog, I found multiple rows in pg_init_privs for the same (tmpnsp, tmpname).
I "fixed" it manually by removing one row from the pg_init_privs table so that it was unique again, and then I ran the upgrade. But I wonder why the upgrade script does not support multiple rows here. At first, I was going to do dismiss it as some strange one-off, but I've encountered this twice now during an upgrade. I'm not sure under what circumstances this occurs exactly though.

[mglonnro]

I had the same thing happening to me with slightly different parameters:

• OS: Debian
• PostgreSQL 13 (but during this process upgraded from 11 to 13)
• TimescaleDB: attempted upgrade from 2.1.1 to 2.3.0
• Installation method: apt-get

charlotte=# ALTER EXTENSION timescaledb UPDATE;
ERROR:  duplicate key value violates unique constraint "saved_privs_tmpnsp_tmpname_key"
DETAIL:  Key (tmpnsp, tmpname)=(_timescaledb_catalog, dimension) already exists.

[ebreijo]

I'm having the same issue when trying to update from 2.1.0 to 2.3.0 on Postgres 13

psql --host=localhost --port=5432 --username=postgres --password --dbname=kyoto --no-psqlrc --command="ALTER EXTENSION timescaledb UPDATE;"
ERROR:  duplicate key value violates unique constraint "saved_privs_tmpnsp_tmpname_key"
DETAIL:  Key (tmpnsp, tmpname)=(_timescaledb_catalog, dimension_slice) already exists.