private synchronized void releaseDataNodeQueryContext() {
    if (dataNodeQueryContextMap == null) {
      // this process is in fetch schema, nothing need to release
      return;
    }

    if (dataNodeQueryContext.decreaseDataNodeFINum() == 0) {
      dataNodeQueryContext = null;
      dataNodeQueryContextMap.remove(id.getQueryId());
    }
  }
All file paths used by this fragment instance must be cleared and thus the usage reference must
be decreased.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/fragment/FragmentInstanceContext.java