# Tree Transform The *Tree Transform* object in Astera Data Stack enables users to transform data in a hierarchical structure. Users can create new fields in the parent node based on the data in the collection/child node. *Tree Transform* supports rule-based routing, filtering, merging, and sorting of data while maintaining its hierarchy. {% embed url="" %} ## **Use Case** In this case, we are using the [*XML/JSON File Source*](https://documentation.astera.com/v/astera-data-stack-v8/dataflows/sources/xml-json-file-source) to extract our source data.
The source file contains customers’ information in the parent node and their orders and shipping details in the collection/child node. You can preview this data by right-clicking on the source object’s *Header > Preview Output.*
A *Data Preview* window will open, displaying a preview of the hierarchical source data.
Now, we want to create a new field in the parent node that contains the count of orders that arrived late for each customer and route these records to a destination file, all while maintaining the hierarchical format of the dataset. This new field in the parent node will depend on two fields: *RequiredDate* and *ShippedDate*, that are already present in the collection/child node. In other words, we are trying to transform hierarchical data without flattening its structure. ## **Using Tree Transform Transformation** 1. To get a *Tree Transform* object from the *Toolbox*, go to *Toolbox > Transformations > Tree Transform* and drag and drop the *Tree Transform* object onto the designer.
The transformation object is empty right now. This is because we have not mapped any fields to it yet. 2. Auto-map source fields onto the transformation by dragging and dropping the root node of the source object *CustomerOrders* onto the root node of the transformation object – *TreeXform*.
Now that the mapping is done, let’s configure the *TreeXfrom* object. ## **Configuring the Tree Transform Object** 1. Right-click on the object’s header and select *Properties* from the context menu. A configuration window for *Tree Transform* will open. The first window is the *Layout Builder* window. This is where we can create or delete fields, change their name or data types, mark any field as a variable, or attach expressions to fields.
2. Create a new field under the parent node. Let’s name it *LateOrders*.
3. Click *Next*, and you will be directed to a *Layout Modifications* window.
4. Select the *LateOrders* field. Here you can modify any field by applying expressions to it.
5. Write the expression that counts the number of late-arriving orders. Click *“…”* next to the expression box to open the *Expression Builder* where you can make use of the extensive library of built-in functions and expressions in Astera.
This creates the field values for *LateOrders* based on the field values of the *RequiredDate* and *ShippedDate* fields. 6. Click on the *Orders* node and a panel *(Options for Collection)* will appear. These options are only available for collection nodes.
*Options for Collection*: * *Show* – Shows collection node in the *Tree Transform* object. * *Flatten With Item Count* – Flattens data based on the record count in the collection node against each item in the parent node. * *Flatten Based on Rules* – Flattens a part of hierarchical data based on predefined rules. * *Route Based on Rules* – Routes and creates subsets of data based on predefined rules. * *Merge With Item Count* – Merges data based on the record count in the collection node against each item in the parent node. * *Hide* – Hides collection node from the *Tree Transform* object. * *Calculation Formula* – An expression box used for writing rules to route or flatten hierarchical data. * *Sort Based On Keys* – Sorts hierarchical data based on the field in the collection node. Only available for *Show* and *Flatten With Item Count* options. This is where we will specify the rule for routing late-arriving orders. Select *Route Based on Rules*. A new section for adding rules will appear in the window.
7. Add a new rule by clicking on the *Add switch condition* icon ![](https://750977703-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FqHxyVNGb7tSdIWecl6Ru%2Fuploads%2Flhu5Y4d3jHd2Zts4IXsD%2Fimage.png?alt=media\&token=82826ec3-37a6-49bd-a1be-d8bdfe29e51e). Now, write an expression to route late arriving orders and name this rule “LateArrivals”.
8. Click *OK*. Now observe that a new collection node *Orders\_LateArrivals* has been added to the *Tree Transform* object.
To preview data, right-click on the header of the transformation object and select *Preview Output* from the context menu.
A *Data Preview* window will open. On expanding the records, you will get corresponding order details and appended details of late-arriving orders.
To store the output for late arriving orders, you can write it to a destination file or use that data further in the dataflow. This concludes using the *Tree Transform* transformation object in Astera Data Stack.