Few questions on postgresql (dblink, 2pc, clustering)

Hi list,

My boss would like to convert from MySQL to PostgreSQL, but there are a few
things that hold us back.

We'd like to have the databases in several physical servers, with referential
integrity between the tables.  Reading from Oracle articles, their
referential integrity can be done using their dblink and triggers.  What I'd
like to ask is whether contrib/dblink is stable?  Seeing dblink in a contrib
directory does bring a doubt (though we've read many success stories with
dblink).  And can the Oracle's way of doing referential integrity be used in
PostgreSQL?  Is it recommended to do that?

I've read the PostgreSQL's TODO list, and I can't find anything about 2-phase
commit being implemented in 8.0.  Is this correct?  Because I also read
there's a 2PC patch being implemented (http://snaga.org/pgsql/).  But
progress seems to have stopped (correct me if I'm wrong).

Basically, our concern is that dblink, 2PC implementation are there, but not
in the PostgreSQL mainstream.

Another thing that bothers us is that we can't find any multi-master
clustering solution in PostgreSQL.  We're actually evaluating MySQL's own
clustering solution, but it's production quality release is still slated for
MySQL 5.0.