Re: group by 3 fields

On Sun, Feb 26, 2017 at 5:05 PM, <marcin.j.nowak@gmail.com> wrote:
>
>
> On Sunday, February 26, 2017 at 12:55:17 PM UTC+1, Daniel Roseman wrote:
>>
>>
>> You should explain what you want to achieve. Grouping is pointless on its
>> own. In any case, when working with an ORM like Django's it is generally not
>> helpful to think in terms of SQL.
>> --
>> DR.
>
>
> Also forget window functions, triggers, conditionals, pubsub and many other
> great db features, just because of Django ORM...
>
> Daniel is right - Django ORM will limit your expressions, but not every ORM
> works that way. SQLAlchemy, in contrast, allows you not only grouping, but
> also wrap anything into their expression API.
>
> With Django there is still possibility to do raw queries, nby
> Model.objects.raw(). I'm doing a complex queries that way, but I'm avoiding
> spaghetti code by using django-sqltemplate. It allows you to write big SQLs
> in separate files (also as templates),load using Django templates engine,
> and finally pass the result directly to Model.objects.raw(), if you want.
>
> You can force grouping, AFAIR. Try to get query object from your queryset,
> i.e. q=Model.objects.all().query and play with q.group_by or something like
> that. But this is kind of nasty workaround. I would not recommend doing
> grouping that way in a project with long-term support.
>
> Generally speaking Django ORM is quite simple, limited and does not work
> well for more complex projects. I don't want to talk more about this,
> because my point of view is generally opposite to the "Django Way" (tm). I
> can just say that I'm using Django ORM as simple mapper for most typical
> cases, leaving more complex things for better tools.
>
> And, Larry, please never give up and always think about db and data first,
> then about application layer. Data is most important. It's lifetime is much
> longer than any app. Continue thinking about grouping, windowing, indexing,
> fts and so on, and find a way how to handle such things using tools like
> Django.

I agree with Marcin. The ORM is a tool and the tool should serve its
user, not the other way around. I have an app that has been developed
and deployed over 7 years. At the beginning it only used the ORM. But
over time, due to performance issues, and application requirements,
we've had to move to raw SQL more and more.

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