Property TotalNumberOfTerms

Expert: Return the number of unique terms visited during execution of the query. If there are many of them, you may consider using another query type or optimize your total term count in index.

This method is not thread safe, be sure to only call it when no query is running! If you re-use the same query instance for another search, be sure to first reset the term counter with ClearTotalNumberOfTerms().

On optimized indexes / no MultiReaders, you get the correct number of unique terms for the whole index. Use this number to compare different queries. For non-optimized indexes this number can also be achived in non-constant-score mode. In constant-score mode you get the total number of terms seeked for all segments / sub-readers.