Deleted files still open long after droping a database

Hi List,

I have droped a database a few hours ago to reclaim some badly-needed space,
but that disk space has not been freed yet. Investigating further, there are
lots of deleted but open files that seem to correspond to the droped db, all
open by some postgres process.

A lot of process were db connections to databases other than the droped one
(I'm not using connection pooling). The other process is the autovacuum
launcher. I have reset the various connection processes, but I hesitate to
kill the autovacuum process.

I'm not sure wether that's relevant, but I moved the database to another
server using slony1-2.2.2 before droping it on the old server. There were
already no more slon processes running when I droped the db.

1) why does this happen at all (keeping files from a droped databse open, even
by processes that never connected to that specific db) ?

2) Can the autovacuum launcher process be safely killed (there are no long-
running vacuum queries) ?

3) Is there a generally cleaner way to do all this ?

PostgreSQL 9.1.2 on debian linux squeeze

$ ps aux|grep autovacuum
postgres 5025 0.0 0.2 122992 39124 ? Ss Jan27 14:28 postgres:
autovacuum launcher process
$ sudo lsof +aL1 /path/to/pgsql/
postgres 5025 postgres 9u REG 8,7 4308992 0 14943966
/path/to/pgsql/base/35355/5979724 (deleted)
postgres 5025 postgres 24u REG 8,7 8192 0 14948153
/path/to/pgsql/base/35355/35460 (deleted)
postgres 5025 postgres 35u REG 8,7 286720 0 14947766
/path/to/pgsql/base/35355/5979918 (deleted)
postgres 5025 postgres 63u REG 8,7 1073741824 0 14947390
/path/to/pgsql/base/35355/5979501.1 (deleted)
postgres 5025 postgres 73u REG 8,7 319488 0 14947627
/path/to/pgsql/base/35355/5979758 (deleted)
postgres 5025 postgres 79u REG 8,7 1073741824 0 14947428
/path/to/pgsql/base/35355/5979507 (deleted)
postgres 5025 postgres 84u REG 8,7 1073741824 0 14947317
/path/to/pgsql/base/35355/5979501 (deleted)
postgres 5025 postgres 113u REG 8,7 8192 0 14948150
/path/to/pgsql/base/35355/35398 (deleted)
postgres 5025 postgres 131u REG 8,7 2326528 0 14943967
/path/to/pgsql/base/35355/5979727 (deleted)
postgres 5025 postgres 141u REG 8,7 16384 0 14947008
/path/to/pgsql/base/35355/5979746 (deleted)
postgres 5025 postgres 142u REG 8,7 28991488 0 14944726
/path/to/pgsql/base/35355/5979728 (deleted)
postgres 5025 postgres 146u REG 8,7 1073741824 0 14947442
/path/to/pgsql/base/35355/5979508 (deleted)
postgres 5025 postgres 150u REG 8,7 82337792 0 14947615
/path/to/pgsql/base/35355/5979710 (deleted)
postgres 5025 postgres 169u REG 8,7 37855232 0 14944962
/path/to/pgsql/base/35355/5979729 (deleted)
postgres 5025 postgres 178u REG 8,7 8192 0 14948156
/path/to/pgsql/base/35355/35723 (deleted)
postgres 5025 postgres 179u REG 8,7 1073741824 0 14947429
/path/to/pgsql/base/35355/5979509 (deleted)
postgres 5025 postgres 181u REG 8,7 450560 0 14947764
/path/to/pgsql/base/35355/5979914 (deleted)
postgres 5025 postgres 185u REG 8,7 959111168 0 14946595
/path/to/pgsql/base/35355/5979508.1 (deleted)
postgres 5025 postgres 200u REG 8,7 224239616 0 14947343
/path/to/pgsql/base/35355/5979507.1 (deleted)
postgres 5025 postgres 204u REG 8,7 74473472 0 14947620
/path/to/pgsql/base/35355/5979713 (deleted)
postgres 5025 postgres 208u REG 8,7 106536960 0 14947623
/path/to/pgsql/base/35355/5979719 (deleted)
postgres 5025 postgres 210u REG 8,7 105611264 0 14947619
/path/to/pgsql/base/35355/5979712 (deleted)
postgres 5025 postgres 212u REG 8,7 446078976 0 14947611
/path/to/pgsql/base/35355/5979704 (deleted)
postgres 5025 postgres 216u REG 8,7 75988992 0 14947469
/path/to/pgsql/base/35355/5979509.1 (deleted)
postgres 5025 postgres 222u REG 8,7 513097728 0 14947263
/path/to/pgsql/base/35355/5979501.2 (deleted)
postgres 5025 postgres 239u REG 8,7 119832576 0 14947621
/path/to/pgsql/base/35355/5979716 (deleted)

--
Vincent de Phily