We just updated from Pentaho PDI 7.0 to 8.1 and we see "Using legacy execution engine" in the logs when executing existing transformations.
What do we have to do to eliminate this legacy component?
The "Using legacy execution engine" message simply means that you're using kettle as the engine. This is the default and doesn't necessarily mean you're using an "old" engine that's no longer being maintained or something along those lines.
The reason this is a new message in 8.1 as compared to 7.0 is because 7.1 introduced the Adaptive Execution Layer (AEL) which allows you to submit your transformations to Hadoop to run on the Spark engine.
You can find additional info about that here: Work with Transformations - Pentaho Documentation
Retrieving data ...