Links Interface

In Megaladata, the Links interface is a page/window in port configuration wizards that allows you to map data fields or variables between the input and output datasets of a port.

• The Inputs list shows the fields (or variables) from the dataset the port accepts.
• The Outputs list shows the fields (or variables) that the port will output after transformation or mapping.

You need to map the relevant fields from the Inputs list to the corresponding fields in the Outputs list.

Mapping fields

1. In the Inputs list (left side), click the field you want to map.
2. Drag the selected input field over to the corresponding field in the Outputs list (right side).
3. Release the mouse button. A graphical link appears, connecting the mapped fields.

To delete a specific link, click the  Delete button on that link's line.

Important note: You can only map fields that have compatible data types.

Outputs of an input port

The content displayed in the Outputs list depends on the type of data the input port accepts:

• Table data: If the port accepts table data, the Outputs list shows usage types of the port's output fields, that is, how the node's algorithm will process them.
• Variables: If the port accepts variables, the Outputs list shows the current variable values.

Inputs list toolbar

The toolbar above the Inputs list provides these commands:

•  Get list: Downloads the input fields list if it's currently empty (for example, when importing data from a database using a custom SQL query).

  This command is only available when configuring an output port.

•  Create output: Creates a field in the Outputs list with the same name and type as the selected input field and automatically maps them.

•  Create outputs for all inputs: Creates matching fields in the Outputs list for all fields currently in the Inputs list and automatically maps them.
• Derived columns creation type: This button appears only if the component's algorithm calculates new fields based on the source fields (for example, the Replace component). It determines how these new, derived fields are handled in the output:
  • By default: The behavior (Add or Replace) depends on the specific component.
  • Add: Adds the newly calculated fields to the output dataset alongside the original fields used in the calculation.
  • Replace: Replaces the original fields used in the calculation with the newly calculated fields in the output dataset.

Output list toolbar

The toolbar above the Outputs list provides these commands:

•  Add: Adds a new, unmapped field to the Outputs list and opens the field parameters dialog for configuration.
•  Clone: Adds a copy of the selected field and opens the field parameters dialog.
•  Edit: Opens the field properties dialog for the currently selected field in the Outputs list. You can also open this dialog by double-clicking the field.
•  Move up /  Move down: Changes the vertical position of the selected field in the Outputs list. The top-to-bottom order in this list determines the left-to-right column order in the port's output table.
•  Map columns: Automatically attempts to map fields of the Outputs and Inputs lists based on name and data type compatibility.(See Automapping Fields for more details.)
•  Automapping: Clicking this buttom runs the Map columns action automatically whenever the node is executed.
   Delete all: Removes all fields from the *Outputs list.
• There is also a  Delete option for each separate field in the list; it appears next to the its usage type when you hover over the field. This button deletes the currently selected field from the Outputs list.

Additional wizard commands

These commands often appear below or between the lists:

•  Auto link: Attempts to create links between currently unlinked fields in the Inputs and Outputs lists.
  • This command does not add or remove any fields from the lists.
  • Existing links are not changed.
  • The algorithm matches unlinked fields based on these criteria, in order:
    1. Compatible data type AND matching name (case-insensitive).
    2. Compatible data type AND matching caption (case-insensitive).
•  Delete all links: Removes all existing mapping links between the Inputs and Outputs lists.
•  Rearrange links: Rearranges the fields vertically within their lists to minimize visual clutter from crossing link lines.
•  Show lost links: Highlights fields in the Outputs list that were previously mapped to input fields, but those corresponding input fields are no longer present in the input dataset (this can happen if the upstream data structure changes).

Selecting multiple fields

To select multiple fields simultaneously in either the Inputs or Outputs list:

• Ctrl + click: Hold the Ctrl key and click individual fields you want to select or deselect.
• Shift + click: Click the first field in a desired range, hold the Shift key, and then click the last field in the range. All fields between (and including) the first and last clicked fields will be selected.

You can combine these methods. For example, select a block of fields using Shift + click, then hold Ctrl while clicking to add or remove individual fields from that selection.

Read on: Table Interface