docs: private List<SchemaColumn> findPartitioningColumns() {
          if (m_partitioningColumns != null) {
              return m_partitioningColumns;
          }
  
          m_partitioningColumns = new ArrayList<>();
          assert(getScanPartitioning() != null);
  
          if (getScanPartitioning().getCountOfPartitionedTables() > 0) {
              for (StmtTableScan tableScan : m_subqueryStmt.allScans()) {
                  List<SchemaColumn> scols = tableScan.getPartitioningColumns();
                  if (scols != null) {
                      addPartitioningColumns(scols);
                  }
              }
          }
          return m_partitioningColumns;
      }