Idempotence means that if you execute an operation multiple times, the result will not change after the initial execution. For example, if the operation is a mathematical function, it means that the output does not change when applied again to its own output:
f(f(x)) = f(x)
Most functions you might think of are not idempotent. If you repeatedly compute f(x) = x + 1, for instance, the result will increase by “1” with every iteration.
Given x = 1
f(x) = 1 + 1 = 2
f(f(x)) = 3
f(f(f(x))) = 4
By contrast, the function f(x) = abs(x) is idempotent.
Given x = -11
f(x) = 11
f(f(x)) = 11
f(f(f(x))) = 11
A real-world example of idempotence is a button for a floor in an elevator. An initial press of the button will cause the elevator to move its passengers toward the specified floor. Subsequent pushes will not change the elevator’s behavior.
What Does Idempotence Mean in the Context of Data Integration?
Suppose we have a data warehouse with the following records in a table: