public TAggregationType getAggregationType() {
    return aggregationType;
  }
Generates the parameter part of the function column name.

<p>Example:

<p>Full column name -> udf(root.sg.d.s1, sin(root.sg.d.s1))

<p>The parameter part -> root.sg.d.s1, sin(root.sg.d.s1)
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/parameter/AggregationDescriptor.java