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From Andrus Adamchik <and...@objectstyle.org>
Subject Re: Default values in DB
Date Tue, 24 Jun 2014 18:18:52 GMT


> I think it's just the INSERT command, a solution would be that only
> values are inserted that are not NULL? 


So this would ensure we don’t override the DB defaults. Perhaps you are on to something
here. If you are relying on DB defaults, a NULL value would override those (at least on MySQL).
Though this presents other problems:

* once you save an object, we need to immediately invalidate it, as it doesn’t contain the
defaults that were assigned in the DB.
* we need to tell NULL apart from “no value” when creating an INSERT.

So yeah, maybe we do need an ability to model a column DB-side default value. Somehow in all
the years of Cayenne I didn’t care too much about it, always relying on the app code to
initialize all the defaults per application needs. But if we are to support schemas with DEFAULT
columns we need to make this change. Actually Cayenne runtime doesn’t even care about the
value of the default. Just about the fact that it is there. DDL operations do though.

Something to think about ...

Andrus 

On Jun 24, 2014, at 1:51 PM, Markus Reich <markus.reich@markusreich.at> wrote:

> Hmm, I think it's just the INSERT command, a solution would be that only
> values are inserted that are not NULL? As you check on UPDATE, the SET part
> includes just fields that were really changed?
> 
> or am I missing sthg.?
> 
> 
> 2014-06-16 9:56 GMT+02:00 Andrus Adamchik <andrus@objectstyle.org>:
> 
>> I would personally do it with a postAdd callback, as mentioned in the top
>> thread in Mike’s list.
>> 
>> Andrus
>> 
>> On Jun 13, 2014, at 4:37 PM, Mike Kienenberger <mkienenb@gmail.com> wrote:
>> 
>>> Here are some previous discussions on default values, from most
>>> current to ancient.
>>> 
>>> I don't know if this is a complete list.
>>> 
>>> DB default values
>>> 
>> http://mail-archives.apache.org/mod_mbox/cayenne-user/201309.mbox/%3CCAGscxryKQBpmM+KBMXhbgAG3+uVNFCT-xqE6bhTQPAAQNXv_SQ@mail.gmail.com%3E
>>> 
>>> default value from the modeler ?
>>> 
>> http://mail-archives.apache.org/mod_mbox/cayenne-user/201004.mbox/%3Cz2tc9876dc11004140528vfe2dfa5elf7da53f16eb4a6b6@mail.gmail.com%3E
>>> 
>>> Handling of database NULL - default value column to modeler?
>>> 
>> http://mail-archives.apache.org/mod_mbox/cayenne-user/200808.mbox/%3Cc09652430808200246x24c2b07es97dddbed50959a23@mail.gmail.com%3E
>>> 
>>> Setting Default Values for Entities
>>> 
>> http://mail-archives.apache.org/mod_mbox/cayenne-user/200712.mbox/%3C144462.30563.qm@web52704.mail.re2.yahoo.com%3E
>>> 
>>> 
>>> 
>>> 
>>> On Fri, Jun 13, 2014 at 4:56 AM, Chukwuemeka Mbonu Onwukwe
>>> <mbonu.onwukwe@gmail.com> wrote:
>>>> Hi Markus,
>>>> I think it would make sense.
>>>> Definitely.
>>>> 
>>>> Regards,
>>>> Emeka
>>>> 
>>>> On 13 Jun 2014 09:26, "Markus Reich" <markus.reich@markusreich.at>
>> wrote:
>>>>> 
>>>>> Hi,
>>>>> 
>>>>> would it make sense to add in Cayennen Modeler a field to set a default
>>>>> value. Cayenne set's per default all fields to null, if they weren't
>> set
>>>> in
>>>>> Java?
>>>>> 
>>>>> regards
>>>>> Meex
>>> 
>> 
>> 
> 
> 
> -- 
> *Markus Reich*
> Moosbach 28/2
> 6392 St. Jakob i.H.
> www.markusreich.at / www.meeximum.at
> markus.reich@markusreich.at


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