Re: Design question: are cross database ManyToMany relationships possible
Re: Design question: are cross database ManyToMany relationships possible
- Subject: Re: Design question: are cross database ManyToMany relationships possible
- From: David Avendasora <email@hidden>
- Date: Tue, 09 Aug 2011 13:57:50 +0800
Hey Lars,
In case you didn't see my earlier email, can you write a SQL Query in any other tool (SequelPRO, DbVisualizer, etc) that will do what you want? If you can, then EOF should be able to do it too. If MySQL won't let you join across DBs on physical servers, then there is little EOF can do to change that.
If you can't then you can always write cover methods that will get you a _lot_ of the functionality that a standard modeled relationship would, but you'll have to be careful to not write Qualifiers or SortOrderings that cross the relationship until after the objects are all in memory.
Dave
On Aug 8, 2011, at 6:35 AM, Lars Sonchocky-Helldorf wrote:
>
> Am 08.08.2011 um 00:19 schrieb Cail Borrell:
>
>> Hi Lars,
>>
>> Like Karl said it should pretty much just work.
>>
>> As long as you do not flatten such relationships and also make sure your qualifiers on either side do not include predicates from the other.
>
> The Dbs are two MySQL DBs on different machines, even running different versions of MySQL 5.something. I did flatten the relationships. Maybe that was the cause why it didn't work. I'll try tomorrow at work.
>
>>
>> In short you just need to keep in mind that EOF will generate SQL that tries to join tables from different databases.
>>
>> -Cail
>
> cheers,
>
> Lars
>
>>
>> On 07/08/2011, at 23.37, Karl wrote:
>>
>>> I don’t think that we ever really needed to give much thought to that. Its automatic.
>>>
>>> Karl
>>>
>>> On 2011-08-08, at 12:19 AM, Lars Sonchocky-Helldorf wrote:
>>>
>>>> Dear List,
>>>>
>>>>
>>>> I've got a design question: Is it possible to manage cross database ManyToMany relationships with EOF?
>>>>
>>>>
>>>> Googling the topic brought up:
>>>>
>>>> http://lists.apple.com/archives/webobjects-dev/2003/Feb/msg00395.html
>>>>
>>>> which gives me the faint hope that such things are possible. But then again almost all of the other search results gave me the impression that this isn't possible.
>>>>
>>>>
>>>> Hence my question to the pros: Are such constructs possible, if so what do I have to pay attention to (Of course I tried and failed before asking this question ;-))? What are the pitfalls?
>>>>
>>>> If this is not possible I'd like to know what kind of solutions you use in such situations: duplicate tables (which bear the risk of divergence)?
>>>>
>>>>
>>>> thanks & cheers,
>>>>
>>>> Lars _______________________________________________
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