@Override
    public void free() {
        // Hack!
        // We don't free index for now.
        if (columns != null) {
            for (CachedColumn c : columns) {
                if (c == null) {
                    continue;
                }
                for (DataPack pack : c.packs) {
                    if (pack != null) pack.free();
                }
                for (PackExtIndex extIndex : c.extIndices) {
                    if (extIndex != null) extIndex.free();
                }
            }
            columns = null;
        }
    }
Free the cache content before die.
indexr-segment/src/main/java/io/indexr/segment/storage/CachedSegment.java