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From Aristedes Maniatis <...@ish.com.au>
Subject Re: CayenneRuntimeException: Can't find id
Date Wed, 16 Jan 2008 12:40:22 GMT

On 16/01/2008, at 10:54 PM, Daniel Kvasnička jr. wrote:

> Well, but how scalable is this? If I understand it well, when I have
> 1000 articles in my DB, cayenne 2.0.x will FULLY query for ALL of the
> 1000 articles on EVERY page change, but will take only PKs from the
> result rows beyond 1st page? This seems to me like a pretty extreme db
> server load case.... If I imagine having a portal with thousands of
> people per day browsing through articles... In success stories, there
> are some companies that manage pretty big dbs with cayenne, how do
> they manage these tables with paginated queries? Or am I missing
> smthing?

Firstly, this is really quite fast. We use this approach on a Swing  
application (three tier) with our largest customer now with 120,000  
contacts in one table. Pulling this across the network takes only a  
few seconds. Remember that Cayenne is just fetching the primary key  
from the database for all but the page of data you want to fault.

Secondly, what else can you do? After all, you've asked Cayenne for  
1000 articles (or 120,000 students) and that's what you'll get.  
Perhaps you should qualify your query so that it doesn't return so  
many rows. Or else fetch the data on the first request and keep it in  
a session for the user to step through without creating another  
database query on each page request. Or even just fetch the data into  
some shared context that all users might browse through. Finally, if  
you know exactly which page of data you want, you might explore  
SQLTemplate with a LIMIT, but I don't think you will find it necessary.


Ari Maniatis



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