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Introduce an option to negate the filtering on a queryset #21

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megies wants to merge 1 commit into from
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Introduce an option to negate the filtering on a queryset #21

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19 changes: 18 additions & 1 deletion src/jane/documents/models.py
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Original file line number Diff line number Diff line change
Expand Up @@ -320,7 +320,7 @@ def get_filtered_queryset_radial_distance(
Distance(km=deg2km(max_radius))))
return queryset

def get_filtered_queryset(self, document_type, queryset=None,
def get_filtered_queryset(self, document_type, queryset=None, negate=False,
**kwargs):
"""
Returns a queryset filtered on the items in the JSON document.
Expand All @@ -329,6 +329,12 @@ def get_filtered_queryset(self, document_type, queryset=None,
queryset is passed.
:param queryset: If no queryset is passed, a new one will be
created, otherwise an existing one will be used and filtered.
:type negate: bool
:param negate: When ``negate=True`` then the resulting queryset is
inverted, i.e. the resulting queryset returns all events that do
not match all given criteria. For example, ``.., negate=True,
max_magnitude=1, site="unterhaching")`` returns all events except
events at site Unterhaching that are below magnitude 1.
:param kwargs: Any additional query parameters.

Assuming a key named ``"example"`` in the JSON file you can search
Expand Down Expand Up @@ -362,6 +368,12 @@ def get_filtered_queryset(self, document_type, queryset=None,
``public=True``
``kwargs={"!public": True}``

The resulting query set can be inverted with ``negate=True``::

* For example, using ``.., negate=True, max_magnitude=1,
site="unterhaching")`` returns all events except for events that are
both declared at site Unterhaching and below magnitude 1.

Please note that as soon as you search for a value, all values that
are null will be discarded from the queryset (even if you search for
!=)! This might be changed in the future.
Expand Down Expand Up @@ -448,6 +460,11 @@ def get_filtered_queryset(self, document_type, queryset=None,
else:
raise NotImplementedError()

# if "negate" option is selected: instead of filtering to given
# criteria, filter out all items that match given criteria
if where != [] and negate:
where = ["NOT ({})".format(" AND ".join(where))]

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@barsch barsch May 3, 2016

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Use the Q and ~ operator instead of plain SQL, see also:

http://stackoverflow.com/questions/687295/how-do-i-do-a-not-equal-in-django-queryset-filtering

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@megies megies May 3, 2016 •
edited
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Saw that one, but I didn't know how to use it together with how the json field is set up right now, as I didn't have a template in the source code.
Since these more canonically looking operators aren't used right now (and the rather hacky extra() instead), I figured that maybe they can't be used with the json field right now..

Sorry.. no real django knowledge here, so mostly orienting on the current source..

queryset = queryset.extra(where=where)

if "ordering" in kwargs and kwargs["ordering"] in meta:
Expand Down