Query using nested attributes

[jankislinger]

This allows you to query using nested data, i.e. something like this

{"term": {"data.x": 1}}

This also fixes cases when you want to filter using

• attribute that isn't present in the data. Originally you'd start with doc_val = None and then change it to "None" (string) and then you compare it with selected value (including partial match). That mean that string "one" would match to missing attribute.
• non-string value. that failed on value in doc_val