RE: Queries based on relationship size

From: Kevin Menard (kmenar..ervprise.com)
Date: Thu Feb 21 2008 - 14:40:44 EST

  • Next message: Andrus Adamchik: "Re: Queries based on relationship size"

    Thanks. I'll have to give that a go over the weekend. Unfortunately,
    my API structure is centered around SelectQuery and a visitor for adding
    expressions and orderings. Changing the root query type will require a
    few more changes than I was hoping for. At least it'll give me an
    excuse to finally play with EJB QL. 

    -- 
Kevin Menard
Servprise International, Inc.
Remote reboot & power control for your network
www.servprise.com                  +1 508.892.3823 x308

    > -----Original Message-----
> From: Andrus Adamchik [mailto:andru..bjectstyle.org]
> Sent: Thursday, February 21, 2008 8:56 AM
> To: use..ayenne.apache.org
> Subject: Re: Queries based on relationship size
> 
> EJBQL query with outer joins should help:
> 
> 1. select c from Customer c JOIN c.orderHistory
> 
>     (inner join filters customers with Orders, so this is like a
> regular SelectQuery)
> 
> 2. select c from Customer c LEFT JOIN c.orderHistory d WHERE d is null
> 
>     (outer join combined with the WHERE clause should allow fetching
> customers with no orders)
> 
> Two caveats: we still need to add pagination support per CAY-963; I
> may have taken a few _temporary_ shortcuts in the EJBQL parser that
> may cause trouble with flattened relationships, so let me know if you
> run into problems.
> 
> Andrus
> 
> 
> 
> On Feb 21, 2008, at 3:05 AM, Kevin Menard wrote:
> 
> > Greetings,
> >
> > I'm running into a little difficulty performing a query that I think
> > comes up often enough that it should be fairly straightforward.
> >
> > I have a schema similar to the following:
> >
> > Customer <--- BillingInfo <--- Order
> >
> > I've mapped the read-only relationship "orderHistory" from Customer
> to
> > Order.
> >
> > Now I'd like to perform two queries.  One for customers with orders
> > and
> > one for customers without.  I'd rather not filter in the app itself
> > because I'd like to paginate the result lists.
> >
> > Is there a way to do this without resulting to an SQLTemplate query?
> >
> > Thanks,
> > Kevin
> >
> > --
> > Kevin Menard
> > Servprise International, Inc.
> > Remote reboot & power control for your network
> > www.servprise.com                  +1 508.892.3823 x308
> >
> >
> >

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