RE: Return values ???

Posted in 1999

Gabbard, Mike W. — Wed, 11 Aug 1999 11:31:02 -0500 — source: Informix-list mailing list archive (1991-1998)

I think alot has changed since the 4.?? versions, thats what version I was working with at the time I was told not to use foreach statements. -----Original Message----- From: Art S. Kagel [mailto:kagel@bloomberg.net] Sent: Wednesday, August 11, 1999 9:58 AM To: informix-list@iiug.org Subject: Re: Return values ??? Sorry but I have to agree with Jonathan. FOREACH adds NO unneccessary overhead, never did as far as I know. I have just looked at some .ec code generated by 4GL 6.04, that should be old enough, and the FOREACH loop generated the following sequence: o Push statement string and pop into variable $statement o Prepare statement from $statement o check status of prepare & call fgl_fatal if error o declare cursor for statement_id o check status of declare & call fgl_fatal if error o open cursor_id o check status of open & call fgl_fatal if error o while(1) o fetch cursor_id into variable list o check status of fetch & call fgl_fatal if error o check for status == SQLNOTFOUND & break if TRUE o do some of my processing o call ixrsthwm() [This is the only thing I don't know about! Looks like a window management function, but why here?] o do some more of my processing o end while o close cursor_id o test status of close & call fgl_fatal if error Except for that one function call this is good clean code. True some of us would be too lazy to check all of those error returns, but that was one of Jonathan's point, eh? The FOREACH loop handles all of that for you without the pain. Anyone know what that function, ixrstwm() does? Jonathan? Art S. Kagel "Barnes, Steve (IFMG)" wrote: > Jonathan, > > Thanks for the reply. > > I was also told by Informix back in England, that a FOREACH loop had an > unnecessary overhead because it would check if the cursor was open, and then > open it if required, in each loop. This was because the FOREACH had an > implied open at the first call. The OPEN, WHILE etc, had an explicit OPEN, > and the FETCH only had to fetch the data. I think that this may have been > true in the purest sense, but would only make a real difference in a large > foreach with many rows being retrieved. > > Does this sound likely? > > Thanks > > Steve > -----Original Message----- > From: Jonathan Leffler [mailto:jleffler@earthlink.net] > Sent: Tuesday, August 10, 1999 7:26 PM > To: Barnes, Steve (IFMG) > Cc: informix-list@iiug.org > Subject: Re: Return values ??? > > Steve Barnes <SBarnes@IFMG.com> wrote: > > I am curious as to why a FOREACH is considered better than > OPEN, > > WHILE, FETCH, CLOSE. I always thought that for large > numbers of reads, > > the overhead of a FOREACH instead of the alternative had > performance > > impacts. This was the thought a few years ago, and maybe I > am behind > > the times! > > > > Can you please clarify this for me please. > > I'm not sure. Which overheads? There are no overheads that > I know of. > A FOREACH loop is a shorthand for the loop originally shown, > except > that FOREACH correctly avoids fetching any data if the > cursor fails to > open. It is for that sort of reason that the FOREACH loop > is better. > > Jonathan Leffler <jleffler@earthlink.net> wrote: > > Octav Chiriac wrote: > > > [...various variations on PREPARE and DECLARE...] > > > OPEN qCursorName USING var1, var2 > > > > > > WHILE TRUE > > > FETCH qCursorName INTO result1, result2 > > > IF sqlca.sqlcode == NOTFOUND THEN > > > EXIT WHILE > > > END IF > > > > > > -- DO SOMETHING WITH YOUR results > > > > > > END WHILE > > > > > > CLOSE qCursorName > > > > > > FREE ... stuff > > > > It is much better to use a FOREACH loop because it is more > > reliable: > > > > PREPARE p_stmt FROM "EXECUTE PROCEDURE theprocedure(?,?)" > > DECLARE c_stmt FROM p_stmt > > > > FOREACH c_stmt USING var1, var2 INTO result1, result2 > > ...Do Something With Your Results... > > END FOREACH > > > > FREE c_stmt > > FREE p_stmt > > -- > Jonathan Leffler (jleffler@informix.com, > jleffler@earthlink.net) > Guardian of DBD::Informix v0.60 -- see > http://www.perl.com/CPAN > #include <disclaimer.h> > > ------_=_NextPart_001_01BEE3EE.D66DB26C > Content-Type: text/html; > charset="iso-8859-1" > Content-Transfer-Encoding: quoted-printable > > <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> > <HTML> > <HEAD> > <META HTTP-EQUIV=3D"Content-Type" CONTENT=3D"text/html; = > charset=3Diso-8859-1"> > <META NAME=3D"Generator" CONTENT=3D"MS Exchange Server version = > 5.5.2448.0"> > <TITLE>RE: Return values ???</TITLE> > </HEAD> > <BODY> > > Jonathan, > > > Thanks for the reply. > > > I was also told by Informix back in = > England, that a FOREACH loop had an unnecessary overhead because it = > would check if the cursor was open, and then open it if required, in = > each loop. This was because the FOREACH had an implied open at the = > first call. The OPEN, WHILE etc, had an explicit OPEN, and the FETCH = > only had to fetch the data. I think that this may have been true in the = > purest sense, but would only make a real difference in a large foreach = > with many rows being retrieved. > > Does this sound likely? > > > Thanks > > > Steve > <UL><UL> > <A NAME=3D"_MailData">-----Original = > Message-----</A> > From:   Jonathan Leffler = > [<A = > HREF=3D"mailto:jleffler@earthlink.net">mailto:jleffler@earthlink.net</A>= > ] > Sent:   SIZE=3D2 FACE=3D"Arial">Tuesday, August 10, 1999 7:26 PM > FACE=3D"Arial">To: &nb

RE: Return values ???

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