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From Mike Kienenberger <mkien...@gmail.com>
Subject Re: Expression to look for objects with an empty to-many relationship?
Date Fri, 24 Jul 2015 17:15:33 GMT
It''s been a long time since I've done this (years, Cayenne 1.2 with
outer join support), but I seem to recall being about to do this with
a ExpressionFactory.matchExp(path, null).

Like Andrus said, you might need to add a "+" in there to force an outer join.

Sorry I can't be of more help.

It would be great if you submitted an expression type that supported
this trivially.



On Fri, Jul 24, 2015 at 12:56 PM, Hugi Thordarson <hugi@karlmenn.is> wrote:
> Indeed :). I’ve been looking at the Expression classes for a while now and they look
a little daunting. Any recommendations on where to start? Is there a developer guide or an
annotated example implementation somewhere?
>
> - hugi
>
>
>
>> On 24. júl. 2015, at 15:59, Andrus Adamchik <andrus@objectstyle.org> wrote:
>>
>> Classic open source - "scratch your own itch" :)
>>
>>
>>> On Jul 24, 2015, at 6:54 PM, Hugi Thordarson <hugi@karlmenn.is> wrote:
>>>
>>> Thanks Andrus, we’ll revert to EJBQL for now.
>>>
>>> Looks like an excellent opportunity to try and implement my first Expression
class :)
>>>
>>> - hugi
>>>
>>>
>>>
>>>> On 24. júl. 2015, at 15:36, Andrus Adamchik <andrus@objectstyle.org>
wrote:
>>>>
>>>> We should add it. For now OUTER JOIN should do the trick:
>>>>
>>>> "a.paintingArray+ = null"
>>>>
>>>> Also EJBQL syntax supports "IS [NOT] EMPTY" :
>>>>
>>>> "SELECT a FROM Artist a WHERE a.paintingArray IS EMPTY"
>>>>
>>>> Andrus
>>>>
>>>>> On Jul 24, 2015, at 5:51 PM, Hugi Thordarson <hugi@karlmenn.is>
wrote:
>>>>>
>>>>> Hi all.
>>>>> Does Cayenne have an Expression class that allows searching for objects
with an empty to-many relationships? If not, any pointers towards a sensible approach?
>>>>>
>>>>> Cheers,
>>>>> - hugi
>>>>>
>>>>> // Hugi Thordarson
>>>>> // http://www.loftfar.is/ <http://www.loftfar.is/>
>>>>> // s. 895-6688
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>

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