Re: When extended query protocol ends?

Hello Dave,

> Tatsuo Ishii <ishii@sraoss.co.jp> writes:
>> Below is outputs from "pgproto" command coming with Pgpool-II.
>> (Lines starting "FE" represents a message from frontend to backend.
>> Lines starting "BE" represents a message from backend to frontend.)
>
>> FE=> Parse(stmt="", query="SET extra_float_digits = 3")
>> FE=> Bind(stmt="", portal="")
>> FE=> Execute(portal="")
>> FE=> Parse(stmt="", query="SET extra_float_digits = 3")
>> FE=> Bind(stmt="", portal="")
>> FE=> Execute(portal="")
>> FE=> Query (query="SET extra_float_digits = 3")
>> <= BE ParseComplete
>> <= BE BindComplete
>> <= BE CommandComplete(SET)
>> <= BE ParseComplete
>> <= BE BindComplete
>> <= BE CommandComplete(SET)
>> <= BE CommandComplete(SET)
>> <= BE ReadyForQuery(I)
>> FE=> Terminate
>
>> As you can see, two "SET extra_float_digits = 3" is sent in the
>> extended query protocol, then one "SET extra_float_digits = 3" follows
>> in the simple query protocol. No sync message is sent. However, I get
>> ReadyForQuery at the end. It seems the extended query protocol is
>> ended by a simple query protocol message instead of a sync message.
>
>> My question is, is this legal in terms of fronted/backend protocol?
>
> I think it's poor practice, at best.  You should end the
> extended-protocol query cycle before invoking simple query.

From [1] I think the JDBC driver sends something like below if
autosave=always option is specified.

"BEGIN READ ONLY" Parse/Bind/Eexecute (in the extended query protocol)
"SAVEPOINT PGJDBC_AUTOSAVE" (in the simple query protocol)   

It seems the SAVEPOINT is sent without finishing the extended query
protocol (i.e. without Sync message). Is it possible for the JDBC
driver to issue a Sync message before sending SAVEPOINT in simple
query protocol? Or you can send SAVEPOINT using the extended query
protocol.

[1] https://www.pgpool.net/pipermail/pgpool-general/2023-December/009051.html