Deletion of Nodes in Column Tree

This blog post is to share how our team (UI Data Protection Masking for SAP S/4HANA) was able to solve a problem uniquely.

As part of our Policy Builder, we needed a column tree to provide a better UI for the user. We used the class ‘ CL_GUI_COLUMN_TREE’ to create the tree.

To provide a better sense, our display looks like this :

Our aim is to allow the user to delete a Node (eg: Block: SE16 or Block: PA30) from the tree. Scanning through the documentation of the class (CL_GUI_COLUMN_TREE). We found the method  DELETE_NODE.

This method worked fine for a single node, but when we had multiple nodes, we got a short dump :

The analysis of the dump revealed that the reconstruction of the column tree is not handled implicitly through the method. We tried to look for a solution through SAP blog posts and question. (s).

We could not find a fix for this and all the blog posts gave us little hope on how well the COLUMN_TREE as a data structure is suited for deletion. So, we came up with a solution of our own.

As a fix, we modified our mappings before calling this method.

To avoid the need for reconstruction, we saved the NODE_ID of the node which was selected for deletion and implicitly moved it to the bottom of the Column tree and then re-adjusting our database table accordingly.  This allowed the standard method to always delete a leaf node from the tree and circumvent the scenario which was failing.

      IF lv_answer = 1 AND lv_node_id NE lv_last_node_id.
        "Move the node to the last node first and then delete it.
        WHILE lv_count <> ( lv_last_node_id - lv_selected_node_id ).
          move_block(
            EXPORTING
              iv_operation   = 'D'
              iv_node_key    = lv_node_id
              iv_item_name   = lv_item_name
            CHANGING
              ct_policy_rule = ct_policy_rule
          ).
          lv_node_id = lv_node_id + 1.
          lv_count = lv_count + 1.
          CONDENSE lv_node_id.
         ENDWHILE.
      ENDIF.

      gr_column_tree->delete_node(
        EXPORTING
          node_key          = lv_node_id
        EXCEPTIONS
          failed            = 1
          node_not_found    = 2
          cntl_system_error = 3
          OTHERS            = 4
      ).

I feel, our out-of-the-box thinking will have two advantages –

1. Provide developers a way to perform deletion in their column tree.
2. Motivate others to solve problems through an experimental approach.

We also welcome any thoughts of a better approach to handle such scenarios.

Image sources: Screenshots.