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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tatsuo Ishii <ishii@sraoss.co.jp>
cc: pgsql-hackers@postgresql.org
Subject: Re: When extended query protocol ends?
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Comments: In-reply-to Tatsuo Ishii <ishii@sraoss.co.jp>
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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.

I'm disinclined to document, or make any promises about,
what happens if you mix the protocols.

			regards, tom lane