public void modifyConf(Configuration conf) {
      for (CacheOnWriteType cowType : CacheOnWriteType.values()) {
        conf.setBoolean(cowType.confKey, cowType == this);
      }
    }
The number of valid key types possible in a store file
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestCacheOnWrite.java