private void aggregateZStarStatistics(Map<Long, List<Integer>> intervalMap) {
        List<Integer> intervals = intervalMap.get(Feature.Z_STAR_COMPRESSED_ATTRIBUTE_HASH);
        if (intervals != null) {
            ++nZStarDocuments;
            nZStarIntervals += intervals.size();
        }
    }
Indexes a predicate with the given id.

@param docId     a 32-bit document id, returned in the Hit objects when the predicate matches
@param predicate the predicate to index
predicate-search/src/main/java/com/yahoo/search/predicate/PredicateIndexBuilder.java