From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200303201848.h2KImfn29586@candle.pha.pa.us>
Subject: Re: I want to send comments to the backend!
In-Reply-To: <25054.1048185788@sss.pgh.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 20 Mar 2003 13:48:41 -0500 (EST)
Cc: =?ISO-8859-1?Q?Gerhard_H=E4ring?= <lists@ghaering.de>,
	pgsql-interfaces@postgresql.org
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Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Could we change the backend to return NullCommand() if the query string
> > was empty, rather than checking for whitespace directly?  I thought the
> > whitespace test was there only as a performance hack.
> 
> It's not a performance hack; it's a performance loss, because 99.99999%
> of the time the strspn test is wasted.  Don't tell me that empty queries
> are an important case to optimize ;-).
> 
> The only reason that code is still there is that old versions of libpq
> used to need to see a special NullCommand response when they
> deliberately sent empty queries (which IIRC they used to do for NOTIFY
> checks, many years ago before the backend would send NOTIFYs
> unprompted).  I'd prefer to take NullCommand out of the protocol, not

Right.  I am sure it was for that.

> generalize it to understand about comments.  Right now seems to be a
> fine time to think about this, in fact, given that we're hacking the
> protocol anyway.

Yes.

> If we were only dealing with libpq, I think I'd take that code out of
> the backend and modify PQexec to produce a PGRES_EMPTY_QUERY on getting
> only ReadyForQuery from the backend.  I'm not sure whether JDBC or ODBC
> might care about NullCommand responses, though --- anyone know?

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