Database operators for custom fields

[Johannes Schneider]

hey list,

I have a custom Field implemented for one of my models. How do I
implement the database operations (e.g. '==', '!=') for the custom field
which are used to execute database queries?

bg,
Johannes
--
Johannes Schneider
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[Serdar Dalgic]

Hi!

In python, '==' operator is set to '__eq__' and '!=' operator is set
to '__ne__' functions.

See more details in http://jcalderone.livejournal.com/32837.html

And In order to make queries from the ORM, Django uses Managers
https://docs.djangoproject.com/en/dev/topics/db/managers/

So you can write a Manager for the model that has this custom field,
override the __eq__ and __ne__ operations on this custom field and
implement as you like.

Good days!

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[Anssi Kääriäinen]

If I am not mistaken you are trying to alter how .filter(customfield__eq=val) and friends work.

In current Django versions you can't easily customize the SQL generated for ORM lookups. In Django 1.7 (currently in alpha) this is possible using custom lookups. Custom lookups will allow you to alter the SQL generated for different lookups (and also add new lookups if need be). See https://docs.djangoproject.com/en/dev/ref/models/custom-lookups/ for all the details.

 - Anssi

[Johannes Schneider]

thnx, yea that's what I'm looking for. unfortunately I cannot use 1.7 ;(

bg,
Johannes

On 19.02.2014 23:19, Anssi Kääriäinen wrote:
> If I am not mistaken you are trying to alter how
> .filter(customfield__eq=val) and friends work.
>
> In current Django versions you can't easily customize the SQL generated
> for ORM lookups. In Django 1.7 (currently in alpha) this is possible
> using custom lookups. Custom lookups will allow you to alter the SQL
> generated for different lookups (and also add new lookups if need be).
> See https://docs.djangoproject.com/en/dev/ref/models/custom-lookups/ for
> all the details.
>
> - Anssi
>
> On Wednesday, February 19, 2014 1:45:43 PM UTC+2, johannes.schneider wrote:
>
> hey list,
>
> I have a custom Field implemented for one of my models. How do I
> implement the database operations (e.g. '==', '!=') for the custom
> field
> which are used to execute database queries?
>
> bg,
> Johannes
> --
> Johannes Schneider
> Webentwicklung

> johannes....@galileo-press.de <javascript:>

> Tel.: +49.228.42150.xxx
>
> Galileo Press GmbH
> Rheinwerkallee 4 - 53227 Bonn - Germany
> Tel.: +49.228.42.150.0 (Zentrale) .77 (Fax)
> http://www.galileo-press.de/
>
> Geschäftsführer: Tomas Wehren, Ralf Kaulisch, Rainer Kaltenecker
> HRB 8363 Amtsgericht Bonn
>

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