Overview

Multi-level faceting is a feature designed to support visualizing of a hierarchy for the documents matching a query, and support filtering documents on arbitrary levels of the hierarchy. This supports deeper level of analytics over all documents matching a query using multiple fields. Facet Requests are now updated to support specifying multiple levels. Each FacetRequest will include a "next level" which itself will be a FacetRequest. Similarly, Facet buckets are updated to contain responses for the next level of a facet bucket. 

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