I saw the request for Facet Use Cases and thought it might nice to have a container for just that purpose so that everyone can contribute their use cases.
The types of facets we are using (through Bobo Browse, but: happy to switch to HSearch when ready):
Simple
Facet on a single value.
Ability to specify minimum number of keys for facet to show up in the facet result. Use case: if you have a faceted field that can have only two values: true or false, it doesn't make any sense for the facet to be retrieved if all values are true.
Ability to specify minimum number of documents for a facet key to show up in the facet result. Use case: you sometimes want to avoid long sets of facet values with only 1 or 2 related documents when the rest has e.g. thousands
Drilldown
E.g. /United States/Texas/Dallas
The ability for a facet value to contain a tree branch of values. Use case:
Ability to select United States and have the facet result show all the states of the US (assuming there are documents for all states)
Ability to select Texas and have the facet result show all the cities of Texas (assuming there are documents for all cities)
Collection
Ability to facet on a field that is a collection and can have multiple values
Ability to use the selected facets as AND: only show facets that match documents that have all values
Ability to use the selected facets as OR: only show facets that match documents that one or more values
Ability to specify minimum number of keys for facet to show up in the facet result.
Ability to specify minimum number of documents for a facet key to show up in the facet result Use case A user selects a number of skills and we can select x number of skills with the documents being selected with OR based on best results and with AND based on exact matches.
PredefinedRange
Ability to get facet keys back that match a predefined range. Use case: documents with salary x show up in as facets with the predefined ranges and a document count per range
Geolocation
Use case: a user enters a longitude and latitude and the documents are selected based on a radius. The facets show various options to expand or contract the radius: < 5km, 5-10km, > 10km