Re: [HACKERS] First draft of new FE/BE protocol spec posted for comments

Tom Lane wrote:
> Barry Lind <blind@xythos.com> writes:
>>My final question is more of an implementation question than comments on 
>>the protocol itself.  Since the jdbc driver needs to be backwardly 
>>compatible with 7.3 and earlier servers that will speak the 2.0 
>>protocol, what is the recomended way to write the client so that it can 
>>'detect' which protocol to use.
> 
> I'd do it the other way: send a 3.0 connection request and then, if you
> get a "bad protocol" error response, send a 2.0 connection request.
> You do have to be a little careful about parsing the connection response
> since if it's 'E' it might be either 2.0 or 3.0 layout, but that can be
> handled without too much difficulty I think.  (Look at the
> already-committed code in libpq's fe-connect.c.)
> 
OK.  So this is what I plan to do:
First try a 3.0 connection.
If an error response is received from the connection attempt then check 
if the error is in a 3.0 format, if yes then report the error, else if 
not 3.0 format then try a 2.0 connection, if that returns an error then 
report it.

thanks,
--Barry