Suppose I have three models (in pseudocode):
class Foo:
asdf = models.CharField()
class Blah:
qwerty = models.CharField()
class Bob:
foo = models.ForeignKey(Foo)
blah = models.ForeignKey(Blah)
Given a Foo and a list of Blahs (where the length of the list might be
very small (0-10) but also could be quite large (100k+)), what would be
the most efficient way of extracting the appropriate Bob objects? I'd
prefer the results to preserve the order of the Blahs, but failing that
I'd at least need a way of looking up which Blah a Bob instance pairs with
w/o nailing the DB a gajillion times.
Right now I'm working with
Bob.objects.filter(foo=myFoo).filter(blah__in=myBlahs)
But even this doesn't really meet my preserving order requirement as I'm
assuming the "in" filter doesn't guarantee order preservation anyways
(although I could order the Blahs by ID and then do an
order_by('blah_id') I would imagine).
I could obviously do something like:
(Bob.objects.filter(foo=myFoo).filter(blah=x) for x in blahs)
but that seems inefficient in that it would be hitting the DB for every
blah.
Does anyone have any advice here?
-J
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