Re: Fast and Easy way to check if an instance of an Model exists in the Database

thnx for this suggestion. we use '_state.adding' now. Is there an
advantage of using '_state.database'?

bg,
Johannes

On 17.01.2014 14:39, Tom Evans wrote:
> On Thu, Jan 16, 2014 at 5:23 PM, Johannes Schneider
> <johannes.schneider@galileo-press.de> wrote:
>> This could be a way to it, but we need this information while handling the
>> Pre_save singal. So this does not work too.
>
> Abuse the django model instance's internals and look to see what
> database this instance was loaded from - if it is None, it hasn't come
> from the database.
>
> This is highly fragile - using an undocumented API that I know has
> changed in recent versions. Personally I would test that the pk does
> not exist in the database (and buy faster hardware.)
>
>
>>>> u=User.objects.get(id=1)
>>>> u2=User()
>>>> u._state.db
> 'default'
>>>> u2._state.db
>>>>
>
> Cheers
>
> Tom
>


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Johannes Schneider
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