public interface Projection<V> extends Map<V,Set<Long>>
Projection is an inverted data set in the form of a one-dimensional
mapping from value (Object) to a set of records. Conceptually, A
Projection is similar to a single row in an index table.clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, equals, forEach, get, getOrDefault, hashCode, isEmpty, keySet, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size, values