Re: Vacuum not removing dead tuples

Rui DeSousa wrote:
> Is there a reason vacuum will not remove dead tuples other than the usual suspects?
> There are no two phase transactions and even after a restoring the database
> from binary backup with nothing connect to the restored instance;
> vacuum still does not remove the dead tuples.

There are three possibilities:

1) Active transactions:

SELECT backend_xmin, xact_start, datname, pid, query
FROM pg_stat_activity
WHERE state <> 'idle'
ORDER BY xact_start;

2) Prepared transactions:

SELECT xid, prepared
FROM pg_prepared_xacts;

3) Lagging replication slots:

SELECT xmin, slot_name, active, active_pid
FROM pg_replication_slots;

The "xid" columns will tell you which tuples VACUUM can
remove: Any tuple with "xmax" less than this are fair game.

Yours,
Laurenz Albe