Creating sequential operators

Sequential operators execute on a single processing node. The nature of some operations, such as reading or writing a file, is inherently sequential, so it makes sense to define sequential operators for such jobs.

There are no restrictions on mixing parallel and sequential operators within a job. The following example uses both sequential and parallel operators:

Figure 1. Example of parallel and sequential operators

All sequential operators define a collection method specifying how a sequential operator combines the partitions of an input data set for processing by a single node. The collection method can be either supplied by the framework or defined by you.