Rather than query on a cost range, is it possible to create "range buckets"?
E.g, you could have buckets defined like this:
1: < 100
2: 100 - 199.99
3: 200 - 299.99
4: 300 - 399.99
5: >= 400
Then, in your model, you'd have a ComputedProperty:
def MyModel(ndb.Model):
cost = ndb.FloatProperty(required=True)
score = ndb.IntergerProperty(required=True)
...
* cost_bucket = ndb.ComputedProperty(repeated=True, name='cb', lambda
entity: MyModel.compute_cost_bucket(**entity**), indexed=True)*
@classmethod
def compute_cost_bucket(cls, entity):
if entity.cost < 100:
return ['1']
if entity.cost < 200:
return ['2']
...
Then you can query by an equality filter on your cost_bucket, but order by
score:
query = MyModel.query().filter(MyModel.cost_bucket ==
'1').order(MyModel.score)
You can have more cost buckets yielding a longer list of values, possibly
even overlapping buckets, but the key thing is that you're only ever
querying on one equality filter. So, for example, you could create a bucket
called '1-2' that was for <200.
Caveat: deserializing a long list from a protocol buffer can be slow;
projection queries can help if it becomes a problem. Also, writing a long
list of indexed values costs $$.
Finally, the name 'cb' above is just a small storage optimization because
the name is repeated in the protocol buffer for each value.
j
On Monday, 5 November 2012 08:33:16 UTC-6, Guillaume wrote:
>
> Hi all,
>
> I want to query all entities with a property (called "cost") within a
> given range, and order the results according to another property (called
> "score"). Both are integers.
> According to the doc, I cannot do that because I should order by the
> "cost" first...
>
> Then I thought I could use a ListProperty of 2 elements : [cost, score].
> Provided that the range of possible values do not intersect, I could
> filter and order the way I want.
>
> Is it a valid approach ?
>
> Thanks
>
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