If you have CFS enabled today, and pooling is enabled (either directly
or because you've pulled an NRT reader), IndexWriter will hold open
SegmentReaders against the non-CFS format of each merged segment.
So even if you close all NRT readers you've pulled from the writer,
you'll still see file handles open against files that have been
This count will not grow unbounded, since it's limited by the number
of segments in the index, but it's still a serious problem since the
app had turned off CFS in the first place presumably to avoid risk of
too-many-open-files. It's also bad because it ties up disk space
since these files would otherwise be deleted.