[patch] Add optional flat values() to QuerySet

Diff against trunk revision 3522

This is my first attempt to contribute code to Django. I added a couple of tests to the lookup tests, I hope they are appropriate.

An alternative approach, as suggested by Gary Wilson in the thread linked above, is to add a separate method to QuerySet? objects:

Maybe .flatvalues("id", "name") or .valuelist("id", "name")

If that is the preferred route, I would vote for 'valuelist' as the name of the method.

I'd like to suggest .items("id", "name"). With no parameters, it would would default to all fields in creation order.

This maps up nicely with dictionary object's "items" method.

I'd like to suggest .items("id", "name"). With no parameters, it would would default to all fields in creation order.

This maps up nicely with dictionary object's "items" method.

I'm not so sure about this. The dictionary object's "items" method returns tuples of (key, value) in a dictionary, whereas the whole point of this flag/new method is to remove the keys altogether, when you just want some values. So naming the same as the dictionary method would be misleading.

Thanks for the patch! Could you rewrite it (and the unit tests) to be a separate method called .valuelist?

A new patch is attached, valuelist.diff, which creates a new method called valuelist(). This patch adds a new class, ValueListQuerySet, which inherits from ValuesQuerySet. I factored some of the logic out of ValuesQueryset's iterator() method into a get_columns() method and a get_field_names() method, so that the same logic could be used in the ValueListQuerySet object.

There are two doctests added, and they both pass.

I hope this is an appropriate solution.

P.S. The last diff I attached could not be previewed by Trac for some reason. I'm about to attach a new one. If it doesn't work either, does anyone have any idea what I'm doing wrong?

Patch which implements valuelist() method

I'll merge this into the ongoing query rewrite.

Thanks for the patch Will. I finally needed to get a list of ids the other day and was remembering about this. Sadly, it's not yet merged :(

A good point is made here: http://groups-beta.google.com/group/django-developers/browse_thread/thread/22b44f4eafaf956a/1515cf99737ab589#1515cf99737ab589

I'd also prefer a way to ensure tuples are always returned.

This needs a decision on how to treat single-field lists, see thread in comment above.

I'm not a huge fan of valuelist() since it smells a bit of creeping featurism, but since Adrian likes this I'll go ahead and mark it accepted.

(In [7149]) queryset-refactor: Added valuelist() method to querysets. Refs #2482.

(In [7477]) Merged the queryset-refactor branch into trunk.

This is a big internal change, but mostly backwards compatible with existing code. Also adds a couple of new features.

Fixed #245, #1050, #1656, #1801, #2076, #2091, #2150, #2253, #2306, #2400, #2430, #2482, #2496, #2676, #2737, #2874, #2902, #2939, #3037, #3141, #3288, #3440, #3592, #3739, #4088, #4260, #4289, #4306, #4358, #4464, #4510, #4858, #5012, #5020, #5261, #5295, #5321, #5324, #5325, #5555, #5707, #5796, #5817, #5987, #6018, #6074, #6088, #6154, #6177, #6180, #6203, #6658