public Metadata getMetadata() {
    return metadata;
  }
A carrier of core, global, non-derived services for planner and analyzer. This is used to ease
the addition of new services in the future without having to modify large portions the planner
and analyzer just to pass around the service.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/PlannerContext.java