How to use an index in couchbase lite api

How can I instruct the query builder which index to use by name
I know the engine can pick whatever index matches the query, but it’s not always accurate to my needs, so I need to specify which index the query going to use by the QueryBuilder “API” not sql++/N1QL

CBL doesn’t have the API to specify the index to use for the query. The index to use is selected by the query’s planner (SQLite Query Planner). You may post the problem that you have about the index is not selected as expected.