code: private void clean(Connection conn) {
          this.selectColumns = null;
          this.isSQLLimit = false;
          this.orderBySQL = new StringBuilder();
          this.conditionSQL = new StringBuilder();
          this.paramValues.clear();
          this.excludedColumns.clear();
          this.updateColumns.clear();
  
          ifThen(localConnection.get() == null && conn != null,
                  () -> conn.close());
      }
docs: Clear the battlefield after a database operation.
  
  @param conn sql2o connection