What does it mean when a PostgreSQL process is "idle in transaction"?
On a server that I'm looking at, the output of "ps ax | grep postgres" I see 9 PostgreSQL processes that look like the following:
postgres: user db 127.0.0.1(55658) idle in transaction
Does this mean that some of the processes are hung, waiting for a transaction to be committed? Any pointers to relevant documentation are appreciated.
The PostgreSQL manual indicates that this means the transaction is open (inside BEGIN) and idle. It's most likely a user connected using the monitor who is thinking or typing. I have plenty of those on my system, too.
If you're using Slony for replication, however, the Slony-I FAQ suggests idle in transaction may mean that the network connection was terminated abruptly. Check out the discussion in that FAQ for more details.
This thread doesn't answer it outright, but may be helpful:
As mentioned here: Re: BUG #4243: Idle in transaction it is probably best to check your pg_locks table to see what is being locked and that might give you a better clue where the problem lies.