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From "Gelhar, Wallace Joseph" <GELHA...@uwec.edu>
Subject RE: Query startAt endAt
Date Tue, 18 Nov 2003 17:58:45 GMT
Hi Jakob,

Will you elaborate on how the current paging works?  What are the driver / platform requirements
to make it work? 

I ask because I have never gotten paging to work for startAtIndex > 0.

My platform is WinXP / Tomcat 4.1 / MS SQL Server 2K / MS JDBC Driver.

My extremely crude hack is too retrieve an iterator and count the index to materialize the
relevant objects. 

Any suggestions?

Wally Gelhar

-----Original Message-----
From: "Jakob Bräuchi" [mailto:jbraeuchi@gmx.ch] 
Sent: Tuesday, November 18, 2003 9:09 AM
To: thma@apache.org
Cc: ojb-dev@db.apache.org
Subject: Re: Query startAt endAt


hi all,

i have to inform you, that paging by SQL is not yet an option :( because we execute a select
for each extent. but i think i found a way to improve OJB-paging be it for collections or
iterators.

as soon as time permits i will start working on the new solution. 


jakob

> Hi Jakob
> 
> <snip>
> >>
> >> Personally, I prefer LIMIT and OFFSET approach. Try to explain:
> > 
> > 
> > i also prefer the OFFSET and LIMIT.
> 
> +1
> 
> cu,
> Thomas
> 
> > we do have a problem with dbms only
> > supporting OFFSET (oracle, sapdb etc.) there is a way to solve this 
> > problem by using an enclosing query:
> > 
> > select * from
> > (
> >   select ... , rownum as ojb_rnum where .... order by ...
> > ) where ojb_rnum between OFFSET and OFFSET + LIMIT
> > 
> > 
> > jakob
> > 
> > 
> >>
> >> StartAt = OFFSET
> >> endAt = OFFSET + LIMIT
> >>
> >> But:
> >>
> >> "endAt" indicates that it need to end at a given index. But this 
> >> index does not necesary exists. Suppose 5 row in a table and we 
> >> use:
> >>
> >> startAt = 1, endAt = 10
> >>
> >> The "endAt" index never will be reached. For me the endAt in this 
> >> case does not exactly describe what we are requesting.
> >>
> >> On the other hand:
> >>
> >> startAt = 1, limit = 10 => This is correct, it means we will start 
> >> at 1 and we will retrieve at max 10 rows. But there is not an 
> >> implicit index of the  last one. Also using limit= 10 avoid us to 
> >> doing some innecesary "maths". We cleary express the max. amount of 
> >> rows we expect to recieve in
> >> a very easy way. It is easier from a programming view. You will not
> need
> >> to sum the 2 values to get the endAt value.
> >>
> >> I just tried to explain my view point. Of course, comments are
> >> welcome. :-D
> >>
> >> Best Regards,
> >>
> >> Antonio Gallardo
> >>
> >> -------------------------------------------------------------------
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> >>
> >>
> > 
> > 
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> > 
> > 
> 
> 
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