This test method and rule is not currently in the master branch, but it does appear in the patch posted for constant expression folding during planning,
DRILL-2060. Once it is merged, the test TestConstantFolding.testConstExprFolding_InSelect() which is currently ignored, will be failing. The issue is that even though the constant folding rule for project is firing, and I have traced it to see that a replacement project with a literal is created, it is not being selected in the final plan. This seems rather odd, as there is a comment in the last line of the onMatch() method of the rule that says the following. This does not appear to be having the desired effect, may need to file a bug in calcite.
Here is the query from the test, I expect the sum to be folded in planning with the newly enabled project constant folding rule.
There also some planning bugs that are exposed when this rule is enabled, even if the ReduceExpressionsRule.PROJECT_INSTANCE has no impact on the plan itself.
It is causing a planning bug for the TestAggregateFunctions.testDrill2092
as well as TestProjectPushDown.testProjectPastJoinPastFilterPastJoinPushDown(). The rule's OnMatch is being called, but not modifying the plan. It seems like its presence in the optimizer is making another rule fire that is creating a bad plan.