@Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }

    NullIfExpression that = (NullIfExpression) o;
    return Objects.equals(first, that.first) && Objects.equals(second, that.second);
  }
NULLIF(V1,V2): CASE WHEN V1=V2 THEN NULL ELSE V1 END
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/sql/ast/NullIfExpression.java