@Override public AutocompleteTags autocompleteTags() {
    if (tagStore == null) {
      synchronized (this) {
        if (tagStore == null) {
          tagStore = new CassandraAutocompleteTags(this);
        }
      }
    }
    return tagStore;
  }
{@inheritDoc} Memoized in order to avoid re-preparing statements
zipkin-storage/cassandra/src/main/java/zipkin2/storage/cassandra/CassandraStorage.java