Streaming Replication Hooks

Hi All,

I hope this is the correct mailing list to ask this question.

We are setting up a system using postgresql 9.1 and streaming
replication to copy reference data from a single central location to
several remote sites. The database changes will come in clumps with
long periods of no activity in between. I would like to add some kind
of programmatic hook to tell us that new changes have been received from
central so that we can trigger messages to be sent out to devices on the
site that may require updates of their data so that I don't have to rely
on polling the database(s).

Is there any way to hook at this point? Even if it didn't tell exactly
what had changed, just that a particular database or table had been
modified that would be perfect. I don't mind what language is required
either.

I found reference to wal_sender and wal_receiver hooks which sounds very
close to what I need, but I suspect that wal_receiver is processed
before the data is applied to the database and I would like a hook after
the database has been updated.

I am assuming that normal triggers cannot be used on a replicated
database? Can someone confirm or deny this?

Thanks in advance.

Dave Fennell