Dmitriy Igrishin <dmitigr(at)gmail(dot)com> writes:
> It seams, that all of the error codes should be obtained by calling
> PQresultErrorField().
> But this function works only with results. So in what situations
> TOO MANY CONNECTIONS error may be thrown after successfully connection ? :)
It isn't.
The lack of a way to report a SQLSTATE code for a connection failure is
an API shortcoming in libpq; it's not the backend's problem.
regards, tom lane