This feature is to detect whether there is overlap among rows in a decision table. If there are overlaps, you can use it to quicky find where the overlaps are among the rows.
To use this function, you need to firstly choose a decision table which you want to detect overlap, and click “Settings” button icon at the top right corner of the selected decision table, then select “Check overlap” from the drop-down menu.
After clicking “Check overlap”, you can see the overlaps among the rows for the selected decision table.
The check compares every pair of rows. Two rows overlap when one input can satisfy both rows.
When overlaps exist, the result opens in a window titled “Overlap detected”. Each overlap is listed as a pair of rows with the conditions that overlap. The window shows at most 10 overlaps with the message “Max 10 overlaps shown”.
Some row pairs cannot be compared. Examples include a text test against a numeric range, a negation, and a presence test against a value. These rows appear under “Rows the checker could not compare” with the two operators. The message tells you to review them by hand. When no overlaps exist among the rows that could be checked, the window says “No overlaps found among the rows that could be checked.” When no overlaps exist, the window is titled “Check overlap”.
A catch-all row has no conditions or has “any value” for every condition. It would overlap every other row, so the check reports it separately under “Catch-all row” instead of listing it as an overlap. The check assumes that the last matching row wins. A catch-all row is fine as the first row because later rows can override it. In the middle, it overwrites every row above it and is overwritten by every row below it. As the last row, it always matches and overwrites the result of any earlier matching row. More than one catch-all row is likely a mistake.
The check requires a table with rows and the user needs the release right. If the table has no rows, it returns the error code decision_table_rows_empty. The scan stops after 10 seconds on very large tables.