Ryszard Lach <ryszard(at)lach(dot)name> writes:
> It seems, that empty statements are generated during opening of
> connection.
Hmm. Try asking about that on the pgsql-jdbc list. I think the JDBC
driver must actually be sending empty commands.
Looking at the backend code, I realize that 7.4 will emit LOG: entries
for empty query strings, whereas prior releases would not. This isn't
a bug IMHO, but it does explain why you are noticing output that wasn't
there before you updated to 7.4.
regards, tom lane