From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Gerhard Häring <lists@ghaering.de>
Cc: pgsql-interfaces@postgresql.org
Subject: Re: I want to send comments to the backend!
Date: Thu, 20 Mar 2003 13:04:03 -0500 (EST)
Message-ID: <200303201804.h2KI43b23863@candle.pha.pa.us> (raw)
In-Reply-To: <24626.1048181454@sss.pgh.pa.us>
Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Yes, I see that now. res is NULL and PQresultStatus() is returning
> > PGRES_NONFATAL_ERROR. What is strange is that "" and "\n" both return
> > an OK result, so I am trying to figure out why comments are different.
>
> The backend special-cases an input string that contains only whitespace
> (look in postgres.c). The special case doesn't apply here, though.
>
> >> Perhaps PGRES_EMPTY_QUERY would be more appropriate? Not sure where in
> >> the chain would be best to change the behavior, though.
>
> > Yes.
>
> Well, we could change the backend --- but that would be a nontrivial
> change, and to tell you the truth I think the special response for empty
> query is a wart on the protocol anyhow. In the long run I'd rather get
> rid of it.
Yes, I see that now:
if (strspn(parser_input->data, " \t\r\n") == parser_input->len)
> Or we could change PQexec to return a PGRES_EMPTY_QUERY result if it
> gets nothing back from the backend except ReadyForQuery. Question is,
> does that create the possibility of masking error conditions?
>
> Or we could just change PQresultStatus to return PGRES_EMPTY_QUERY for
> a null input. Attractive 'cause it's a one-line change, but I think it
> really does create the possibility of masking errors --- application
> programmer errors, mostly.
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. In fact, the
comment in postgres.c says that:
* if there is nothing in the input buffer, don't
* bother trying to parse and execute anything; just
* send back a quick NullCommand response.
In pg_exec_query_string(), if nothing is processed, we can do the call
there. or course assuming destination is correct?
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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To: pgsql-interfaces@postgresql.org
Cc: pgman@candle.pha.pa.us, tgl@sss.pgh.pa.us, lists@ghaering.de
Subject: Re: I want to send comments to the backend!
In-Reply-To: <200303201804.h2KI43b23863@candle.pha.pa.us>
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