@Override
  public Pattern<JoinNode> getPattern() {
    return PATTERN;
  }
Joins support output symbol selection, so make any project-off of child columns explicit in
project nodes.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/iterative/rule/PruneJoinChildrenColumns.java