2015-01-04 19:02 GMT+03:00 <sftf-m...@mail.ru>: > Hello! > Question generally to (libpq) developers. > > According to http://www.postgresql.org/docs/9.4/static/libpq-async.html: > "PQsendQuery cannot be called again (on the same connection) until > PQgetResult > has returned a null pointer, indicating that the command is done." > > As I guess this is also true for all PQsend* functions, like > PQsendQueryPrepared, > although this is not explicitly stated in the documentation. > > So question is why this limitaion exists? > Because it's violates the protocol -- sending messages like Parse or Bind to the backend until the CommandComplete or ErrorResponse consumed by the frontend is wrong. See - http://www.postgresql.org/docs/9.4/static/protocol-flow.html
> Why PQgetResult(PGconn *conn) operates on connection, > and not on some unique handler that each "PQsend*" could return. > It does not make sense because of the message flow described by the protocol. > > Is it limitaion of libpq or architecture of postgresql backend or > backend-frontend protocol? > > PS. If you need pipelining take a look at the thread "libpq pipelining" in hackers-. -- // Dmitry.
