nextMappedDoc
Like .nextDoc but skips over unmapped docs and returns the next mapped doc ID, or DocIdSetIterator.NO_MORE_DOCS when exhausted. This method sets .mappedDocID as a side effect.
Like .nextDoc but skips over unmapped docs and returns the next mapped doc ID, or DocIdSetIterator.NO_MORE_DOCS when exhausted. This method sets .mappedDocID as a side effect.