Database Reference
In-Depth Information
Figure 24-6. An assembly of operations
The Each and Every pipes provide a simple mechanism for selecting some or all values
out of an input tuple before the values are passed to its child operation. And there is a
simple mechanism for merging the operation results with the original input tuple to create
the output tuple. Without going into great detail, this allows for each operation to care
only about argument tuple values and fields, not the whole set of fields in the current input
tuple. Subsequently, operations can be reusable across applications in the same way that
Java methods can be reusable.
For example, in Java, a method declared as concatenate(String first,
String second) is more abstract than concatenate(Person person) . In the
second case, the concatenate() function must “know” about the Person object; in
the first case, it is agnostic to where the data came from. Cascading operations exhibit this
same quality.
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