Inequality Filter in AppEngine Datastore

Question

I understand that Google AppEngine supports only one inequality filter per query. What are the workaround on this limitation? Are there any solution that will provide similar effect?

Answer 1

Actually GAE supports multiple inequality filters as long as they are on the same property.

The workarounds to this limitation are data-specific, e.g. it depends how your data is structured and how you want to query it. For example, for geo searching, as @Dan Holevoet mentioned, there are various geo-hashing algorithms. Basically all such algorithms involve combining multiple properties into one and at the same time quantizing the property (creating discrete values). For example geo-hashing involves dividing up the world map into small fixed-size areas (= combining lat/lon and quantizing) in order to be able to search via equality operator.

Answer 2

Whether there is a workaround for having a single inequality filter per query depends on the type of dataset you are querying over.

For instance, if you wanted to query positional data using a latitude and longitude address, you'd typically need to query for a range of values on two properties (lat and long). However, with a geohash algorithm you can accomplish an equivalent query using only a single property.