Error in DROP TABLESPACE

INTERNAL

Hi,

I've run into an odd problem - I have what seems to be a "zombie" tablespace
that PostgreSQL won't let me drop, but nothing inside it is active.

drop tablespace ts_idx_wb2;
ERROR: tablespace "ts_idx_wb2" is not empty

postgres=# \db+ ts_idx_wb2
List of tablespaces
Name | Owner | Location | Access privileges | Options | Size | Description
------------+----------+----------------------------------+---------------------+---------+--------+-------------
ts_idx_wb2 | postgres | /pgsql/postgres/tsdata1/ts_idx_wb2 | postgres=C/postgres+| | 250 GB |
| | | mydatabase=C/postgres | | |
(1 row)

Check on filesystem location.
On the filesystem there are files related only to fileref 515555188:

postgres(at)myserver:/pgsql/postgres/tsdata1/ts_idx_wb2/PG_12_201909212/16419> ls -la
total 261854080
drwx------ 2 postgres postgres 69632 Apr 22 17:45 .
drwx------ 3 postgres postgres 4096 Oct 31 2024 ..
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.1
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.10
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.100
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.101
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.102
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.103
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.104
...
...
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.97
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.98
-rw------- 1 postgres postgres 1073741824 Oct 31 2024 515555188.99

SELECT pg_tablespace_databases((SELECT oid FROM pg_tablespace WHERE spcname = 'ts_idx_wb2'));
pg_tablespace_databases
-------------------------
16419

SELECT oid, datname FROM pg_database WHERE oid = 16419;
oid | datname
-------+-----------
16419 | mydatabase <----------------

Connected to database mydatabase:

select cl.relfilenode, nsp.nspname as schema_name, cl.relname, cl.relkind
from pg_class cl
join pg_namespace nsp on cl.relnamespace = nsp.oid and cl.relfilenode=515555188 ;
relfilenode | schema_name | relname | relkind
-------------+-------------+---------+---------
(0 rows)

To be sure I run the same query on the other databases with the same result (0 rows)

So there are no actual references to these files, yet the relationship
persists sufficiently for the DROP TABLESPACE to error out.
My guess is that the files belong to an index being moved on Oct 31 to ts_idx_wb2 tablespace, and during the move the
postgres instance crashed due space shortage on wal filesystem, and this crash left this "zombie" files on the filesystem.

In order to drop the tablespace, is it safe to shut that postmaster down and manually remove the contents of this
directory?

Thanks
Gabriele Fagnani