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Querysets now utilises a local cache

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Changed __len__ behavour in the queryset (#247, #311)
This commit is contained in:
Ross Lawley 2013-05-10 13:57:32 +00:00
commit 9251ce312b
6 changed files with 204 additions and 56 deletions
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docs/upgrade.rst
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@ -235,12 +235,15 @@ update your code like so: ::
mammals = Animal.objects(type="mammal").filter(order="Carnivora") # The final queryset is assgined to mammals
[m for m in mammals] # This will return all carnivores
No more len
-----------
Len iterates the queryset
--------------------------
If you ever did len(queryset) it previously did a count() under the covers, this
caused some unusual issues - so now it has been removed in favour of the
explicit `queryset.count()` to update::
If you ever did `len(queryset)` it previously did a `count()` under the covers,
this caused some unusual issues. As `len(queryset)` is most often used by
`list(queryset)` we now cache the queryset results and use that for the length.
This isn't as performant as a `count()` and if you aren't iterating the
queryset you should upgrade to use count::
# Old code
len(Animal.objects(type="mammal"))