What is the sub editor used by Lucene?

Question

I do not know what ReaderUtil.subReader Lucene does. Does anyone know what he is doing?

See the class definition here: ReaderUtil .

Is it used to read each segment separately?

Answer 1

The Lucene metric is segmented. In short, only a subset of the index is read from each segment. And sub-editors are real readers who work directly on a segment (one segment => one segment reader). And the IndexReader that the client uses is an aggregated implementation that uses IndexReader to do the actual work.