Design Planner options

[nathanielc]

Possible options:

• Disable push downs
• Turn of optimization X
• etc

[wolffcm]

Some discussion on Slack with @aanthony1243 about how to get better tracing of Flux execution: we could add a planner option that would inject yield nodes in between plan nodes so that the user can get an idea of the output of their query at each stage.

Taking the idea further, one could imagine extending yield to take an additional fn argument that is an additional aggregation to perform on the yielded data, e.g., yield(name: "range_sum", fn: sum). (This would likely require additional support from the execution engine)

[wolffcm]

I filed #1439 that describes a possible way to do this.