On Thu, 10 Apr 2025 at 11:17, Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
> > > On 2025/04/10 23:40, Dave Cramer wrote: > > > > On Thu, 10 Apr 2025 at 09:54, Fujii Masao <masao.fu...@oss.nttdata.com > <mailto:masao.fu...@oss.nttdata.com>> wrote: > > > > > > > > On 2025/04/10 18:52, Dave Cramer wrote: > > > Greetings, > > > > > > The current docs say that if a client asks for a protocol that > the backend doesn't support, it will return the newest minor version. > https://www.postgresql.org/docs/current/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-NEGOTIATEPROTOCOLVERSION > < > https://www.postgresql.org/docs/current/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-NEGOTIATEPROTOCOLVERSION> > < > https://www.postgresql.org/docs/current/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-NEGOTIATEPROTOCOLVERSION > < > https://www.postgresql.org/docs/current/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-NEGOTIATEPROTOCOLVERSION > >> > > > > > > However that isn't what it returns. It actually returns the > entire newest protocol that it supports. Attached is a patch to fix the > docs. > > > > As far as I read the code, the server returns the protocol version > requested by > > the client if it's less than or equal to the latest version the > server supports. > > Otherwise, it returns the latest supported version. So the proposed > description > > doesn't seem accurate either, does it? > > > > I've added a note as to when this is sent. AFAICT through testing and > the fact that the pgjdbc driver has never handled this message > > I'm pretty sure it only sends this message if the requested protocol is > not equal to the protocol the server supports. > > No, the message is also sent when the client requests protocol options that > the server doesn't recognize. In that case, if the client requests an older > protocol version along with unknown options, the server responds with > the requested protocol version, not the latest one. > OK, I hadn't contemplated the unrecognized options. However AFAICT the documentation in the code state /* * If the client requested a newer protocol version or if the client * requested any protocol options we didn't recognize, let them know * the newest minor protocol version we do support and the names of * any unrecognized options. */ and the code agrees that we send the latest protocol version that we support, not the requested one. Dave
protocol-2.patch
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