While doing a verbose vacuum, I'm constantly hitting things like: DETAIL: 3606 dead row versions cannot be removed yet. I believe this is a problem, because I still do have some empty tables requireing up to 3-400 ms just to check if the table is empty (see thread "slow queue-like empty table"). If pg_stat_activity.query_start actually is the start time of the transaction, then we've gotten rid of all the real long-running transactions. Then again, if pg_stat_activity.query_start actually was the start time of the transaction, the attribute would have been called pg_stat_activity.transaction_start, right? Is there any way to find the longest running transaction?
