Hello,
I am a bit stuck on something that I think ought to be really easy (so
I am probably being really stupid!).
I am trying to write a view for a model such that I can pass the view
(via post data) a (or an unknown) number of fields of that model, and
receive back a list of dictionaries of distinct values for those
fields and the number of times that combination of values appears.
So, suppose the model was for holding data about cars, and it had
fields 'manufacturer', 'model', 'fuel_type', 'colour', 'n_of_doors',
etc where the fields had appropriate field types (a mixture of
different field types), I would want to be able to pass the view for
example groupBy=['colour', 'fuel_type'], and it would return a dict of
distinct colour/fuel type combinations and how many cars there are in
the db with those combinations, eg. [{'colour': 'red', 'fuel_type:
'diesel', 'count': 14}, ...].
To me it seems like the kind of thing you would want to use annotate
and Count for, except Count takes one field not multiple fields.
I tried using values() to limit the fields, then python to do the
counting / distinct bit, but it is annoying because I want to be able
to tell it to return the unicode values for foreign keys etc. rather
than ids that would then need to be looked up. Also it is way too
slow.
I am trying to figure a way to do this that is reasonably fast because
I am trying to filter a lot of data. Am I missing something? I haven't
been using python / django much lately so I am probably thinking the
wrong way!
Any help would be appreciated :)
Em
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