Undoing, redoing, and repeating an operation

In Xcalar Design, after you perform an operation, you can undo it. After you undo an operation, you can redo it.

Repeating an operation means redoing an operation that has not been undone. For example, after you sort one column alphabetically, you might want to repeat the sorting on another column.

This section describes how to undo and redo an operation in one of two ways. It requires an understanding of table statuses and dataflow graphs. If you are not familiar with these topics, you can get information from these sections:

Using the Undo and Redo buttons

The (Undo) and (Redo) buttons are located in the upper left corner of the Worksheet window. When you hover over one of these buttons, a tooltip is displayed to indicate what operation will be undone or redone.

The Undo and Redo buttons work for any database operation or any action taken to change the appearance of a table or worksheet. In general, the Undo and Redo buttons are useful when you want to correct a mistake. You cannot, however, undo the action of dropping a table.

EXAMPLE: After you perform a filter on a particular value in a cell, a new version of the table is created with only the rows containing that filtered value in the column. To revert to the version of the table before the filter operation, click Undo.
EXAMPLE: After you minimize a column, you can undo the minimizing by clicking Undo. The column is restored to its original width.
EXAMPLE: After you change the order of the worksheets in the Active Worksheet List, you can click Undo to return the worksheets to the original order.

If a table is created by an operation such as filter, undoing the operation does not remove the table. Instead, the table is included in the Temporary Table list, and clicking a Redo button makes this temporary table active again.

The temporary table exists for as long as the operation can be redone. If after you undo the operation, you perform another action, Xcalar Design drops the temporary table.

EXAMPLE: In a table named Airlines#pT149, you use the Map function to change the data type of a column to Integer. The Airlines#pT150 table is created as a result. Suppose you undo the Map function, Airlines#pT150 is removed from the dataflow graph but retained as a temporary table viewable on the Temporary Table List. You can redo the Map function to make Airlines#pT150 active again. However, if after undoing the Map function, you perform a filter operation, Airlines#pT150 is dropped and cannot be recovered.

Using the dataflow graph

This section describes another way for undoing an operation, which requires an understanding of table statuses and dataflow graphs. If you are not familiar with these concepts, read the following topics:

Use this method when you realize that your modeling steps are not correct and that you want to start over from a particular point of the dataflow graph. By reverting to a selected version of a table in the dataflow graph, you can abandon all the changes made to the table since that version.

The following example illustrates how to undo a Map operation:

  1. Click (dataflow graph icon) in the lower-right corner of the Xcalar Design window.

  2. In the dataflow graph, click the table before the Map operation. A list of options is displayed in a pop-up menu. Click Revert to this table.

  3. To hide the dataflow graph, click again or click the Close button in the upper right corner of the dataflow graph panel.

Xcalar Design removes from the dataflow graph all tables listed to the right of the table to which you revert. In this example, airlines3#XS47 is removed from the dataflow graph and added to the Temporary Tables list. This table is kept as a temporary table until you drop it.

NOTE: Clicking Revert to this table is considered an operation. You can undo or redo this operation through the Undo or Redo button, just as you do with other operations.

Repeating an operation

You can repeat an operation that requires only one mouse click. For example, after you cast one column to integer, you can select another column and perform the same type casting operation. You can select multiple columns for the repeated operation.

To repeat an operation, press Ctrl-y.

NOTE: You can use Ctrl-y to repeat an operation only if it is a one-click operation. For example, you cannot repeat a Map operation because the operation is not a one-click operation. It requires you to enter input in the MAP panel.

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