public FragmentInstanceInfo getInstanceInfo(FragmentInstanceId instanceId) {
    requireNonNull(instanceId, "instanceId is null");
    FragmentInstanceContext context = instanceContext.get(instanceId);
    if (context == null) {
      return null;
    }
    return context.getInstanceInfo();
  }
Gets the info for the specified fragment instance.

<p>NOTE: this design assumes that only fragment instances that will eventually exist are
queried.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/fragment/FragmentInstanceManager.java