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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/db-api.txt | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/docs/db-api.txt b/docs/db-api.txt index 6299f3497d..405ed87cef 100644 --- a/docs/db-api.txt +++ b/docs/db-api.txt @@ -376,6 +376,29 @@ You can evaluate a ``QuerySet`` in the following ways: iterating over a ``QuerySet`` will take advantage of your database to load data and instantiate objects only as you need them. + +Pickling QuerySets +~~~~~~~~~~~~~~~~~~ + +If you pickle_ a ``QuerySet``, this will also force all the results to be +loaded into memory prior to pickling. This is because pickling is usually used +as a precursor to caching and when the cached queryset is reloaded, you want +the results to already be present. This means that when you unpickle a +``QuerySet``, it contains the results at the moment it was pickled, rather +than the results that are currently in the database. + +If you only want to pickle the necessary information to recreate the +``Queryset`` from the database at a later time, pickle the ``query`` attribute +of the ``QuerySet``. You can then recreate the original ``QuerySet`` (without +any results loaded) using some code like this:: + + >>> import pickle + >>> query = pickle.loads(s) # Assuming 's' is the pickled string. + >>> qs = MyModel.objects.all() + >>> qs.query = query # Restore the original 'query'. + +.. _pickle: http://docs.python.org/lib/module-pickle.html + Limiting QuerySets ------------------ |