Drag/Drop - 6.3

Talend Data Mapper User Guide

EnrichVersion
6.3
EnrichProdName
Talend Big Data Platform
Talend Data Fabric
Talend Data Management Platform
Talend Data Services Platform
Talend MDM Platform
Talend Real-Time Big Data Platform
task
Design and Development
EnrichPlatform
Talend Studio

The drag/drop mechanism is used to specify most of the aspects of a map. The simplest operation is to drag an input map element to an output map element. If the output map element had no previous value expression, this creates a value expression that copies the input to the output.

Here are the different possibilities for drag/drop when editing a map:

  • Drag from input map element to:

    • An output map element - If no value expression is present, creates a value expression copying input to output.

    • An empty value expression panel - Behaves identically to dragging to the output map element (assuming the value expression tab is enabled, which occurs when you have previously selected the output map element).

    • An expression - Adds the input map element as the last child of the expression. If the expression is a function argument, only one child to a function argument is allowed.

  • Drag a function to:

    • An output map element - If no value expression is present, the function becomes the root of the value expression tree. Otherwise, has no effect.

    • An empty value expression Panel - Behaves identically to dragging to the output map element (assuming the value expression tab is enabled, which occurs when you have previously selected the output map element).

    • An expression - Adds the function as the last child of the expression. If the expression is a function argument, only one child to a function argument is allowed.

  • Drag an expression to:

    • Another expression - Adds the source expression as the last child of the target expression, and removes the source expression. This is because a drag/drop is identical to a cut/paste operation. A copy/paste will do the same thing, except it will not remove the source expression.

  • Drag from an output map element to:

    • An output map element - Creates a value expression in the destination output with a reference to the source output, unless a value expression is already present in the destination output.

    • An empty value expression Panel - Behaves identically to dragging to the output map element (assuming the value expression tab is enabled, which occurs when you have previously selected the output map element).

    • An expression - Adds the output map element as the last child of the expression. If the expression is a function argument, only one child to a function argument is allowed.

  • Drag from an value map element (input or output) to:

    • An output map element - Creates a Constant expression with the specified value.

    • An empty value expression Panel - Creates a Constant expression with the specified value.

    • An expression - Creates a Constant expression with the specified value.

No other drag/drop operations have any effect when editing a map.

Expanding Map Elements

As mentioned above, map elements correspond with the structure elements. In some cases though structures can be huge with thousands of elements most of which are not mapped. For performance reasons map elements are only materialized if they are actually used in mapping, which happens as you expand the map elements in the designer.

So when editing a map, and simply expanding a map element, you may see the map become unsaved (the asterisk appears in the editor tab); this is normal and indicates that new map elements have been materialized.

When searching through a map, all possible map elements (being searched) are temporarily materialized and then discarded at the end of the search so as not to have a large number of unused elements.