On Tue, Jan 31, 2017 at 9:53 AM, Higuchi, Daisuke <higuchi.dais...@jp.fujitsu.com> wrote: > Hello, > > This this is my first posting to the mailing list. > > I am interested in multiple hosts of libpq , then I found the bug in this > feature. > When I set "target_session_attrs" to "any" and call PQsendQuery, my > application is succeeded. > However, when I set "target_session_attrs" to "read-write" and call > PQsendQuery, "another command is already in progress" is occurred. > I attached the test application to reproduce this problem. > > I think this is because PQgetResult is not called until PQgetResult has > returned a null pointer. > So, I attached the patch for fix this. > >  > https://www.postgresql.org/message-id/flat/20150818041850.ga5...@wagner.pp.ru#20150818041850.ga5...@wagner.pp.ru > Interestingly, when I don't set PGPORT, PGHOST I get the same error with the C program. The patch fixes the problem.
Per the documentation , "PQgetResult must be called repeatedly until it returns a null pointer, indicating that the command is done.". The code in PQgetResult() under CONNECTION_CHECK_WRITABLE case, violates that. The patch fixes it. The patch however jumps to keep_going without changing conn->status, which means that it will end up again in the same case. While that's fine, may be we should use a local loop on PQgetResult() to keep the code readable. I would have added a test with the patch, but it seems we don't have much tests in interfaces/libpq. The bug is pretty trivial and would have been caught easily had we had any tests.  https://www.postgresql.org/docs/devel/static/libpq-async.html -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers