Is it possible to create hierarchical dimensions like countries and cities.
You can define a lookup of the hierarchy in reverse, but you’ll want to start at something as unique as possible.
So you can make a lookup that maps unique_location_name -> general_location_name then use that lookup during your queries.
An example of a unique location name might be a zip code mapping to city, metro area, state, or whatever else.
An example of a non-unique location name would be city. (Quick! Which US state is the city “Springfield” in?)
In general Druid expects data to be denormalized. I’m wondering about your use cases with hierarchical dimensions? For example, if you are trying to answer the top cities for the top states for the top countries, you should look at the queries Pivot issues: https://github.com/implydata/pivot