A Value component selects a value obtains the specified value calculated based on the values from input record and assigns it to the specified variable. It can select the min, max, first, or last value from all the processed records.
You can use the Value component, for example, to store the maximum value of record creation time in a parameter, and query only records with the created time greater than this value during the next data flow execution. Thus, every time the data flow starts, it will process only new records.
To configure the Value component, enter an expression by using our expression syntax into the Value box. In a simple case the expression is just the name of an input column. To create complex expressions use Expression Editor.
Then select the Value type — min, max, first, or last. Finally, specify a Variable to store the value in. You can also provide a Name for the component, which is displayed on the diagram.
The Value component can update the variable either after processing each batch or when data flow completes. The latter is useful if you want to use the variable in other places of the data flow before changing its value. If you want to change the variable value only when data flow completes, select the Value Update On Data Flow Completion checkbox.
The Value component has one input and one regular Default output for successfully processed rows. It sends successfully processed input rows to its output unchanged. It also has the Error output, to which it passes records, for which the expressions failed with an error, and adds the Error column with an error message to them.