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Re: ECPG - cursor fetch

From: Michael Meskes <meskes(at)postgresql(dot)org>
To: Mark Richardson <markmapo(at)yahoo(dot)com>
Cc: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: ECPG - cursor fetch
Date: 2005-03-13 10:57:07
Message-ID: 20050313105707.GA15406@trantor.fam-meskes.de (view raw or flat)
Thread:
Lists: pgsql-interfaces
On Thu, Mar 10, 2005 at 01:51:07PM -0800, Mark Richardson wrote:
> I'm doing a port from Sybase's pre-compiler cpre, to ecpg and I have a couple of questions (if anyone has the time).  This relates to cursors and fetching, and what I would like to do is retrieve a bunch of records at one time - cpre is able to fetch values into an array...
> EXEC SQL BEGIN DECLARE SECTION;
> int myInts[100];
> EXEC SQL END DECLARE SECTION;
> ...
> EXEC SQL DECLARE myCursor FOR SELECT
> myInt FROM myTable;
>  
> EXEC SQL FETCH myCursor INTO
> :myInts;
>  
> There is one mechanism that cpre uses to make sure that you don't exceed the array size...
> EXEC SQL OPEN myCursor ROW_COUNT=100;
> then, every time you do a fetch, it retrives 100 rows.

This is usually done in the fetch statement and not in the open one.
Just use

EXEC SQL FETCH 100 myCursor INTO :myInts;

> Also, since I'm in the middle of a port, I'm trying to make the code work for both with a different compile flag - but the pre-compilers don't care about #defines.  Is there some other mecanism to tell ecpg to ignore or skip a section?  I really don't want to have to make a "Pre-pre-compiler".  

EXEC SQL DEFINE/IFDEF/...

> I thought I would share this - the ecpg pre-compiler is much easier to work with, and it handles things better than cpre when it comes to code generation.  I think it would be much easier to port from ecpg to cpre than what I am doing, because a lot of the non-standard options that are available used/forced in cpre.  So thanks for all the work you guys have done.

Nice to hear that. :-)

Michael
-- 
Michael Meskes
Email: Michael at Fam-Meskes dot De
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes(at)jabber(dot)org
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