Unusable resultset

I just did a query that would have returned impossible amounts of data, 
eg: select * from BIGtable.  I am porting from Informix to Postgresql, 
and I guess I have been spoiled by the IFX JDBC drivers, which return 
only as much data, relatively speaking, as is needed.  When the IFX JDBC 
driver runs out of data, it asks the backend for more data.  Apparently 
the backend caches the results instead of shoving it all down the socket 
to the JDBC driver all at once.  (Oh, how I wish PG JDBC did that.)

Anyway, when I did the above, I got back a null resultset.  I don't even 
think it threw an exception (but I will try to check on that).  All of 
that is fine and can be dealt with.  My real problem is that the 
connection is no longer usable, as ANY query I perform throws a 
"postgresql.con.type" exception.

Why does it do that, and what is a "type" exception?

I now catch this specific exception as an indication that the connection 
is bad, after which I close it, but it sure is annoying to have to put 
driver-specific code in my java codebase.  :(

-- 
Matt Mello