public DocIdSet getDocIdSet(AtomicReaderContext context, Bits acceptDocs) throws IOException {
final AtomicReader reader = context.reader();
this.visitedReaders.add( reader );
OpenBitSet bitSet = new OpenBitSet( reader.maxDoc() );
for ( int i = 0; i < reader.maxDoc(); i++ ) {
bitSet.fastSet( i );
}
Terms terms = reader.terms( fieldName );
TermsEnum iterator = terms.iterator( null );
BytesRef next = iterator.next();
while ( next != null ) {