Hey All, I've been thinking about the SubsetTransformer pattern [1] that we use in Drill to ensure trait propagation. It was discussed here in Calcite [2]
Julian's felt that the correct solution (and the patch he ultimately applied) was to use a create and then remove behavior. Take a look at his revision to my test here [3] where he adds the SortRemoveRule in order to remove an extraneous Sort operation. It seems like we need to either introduce a new mechanism in Calcite to accomplish this or we need to adopt the removal behavior. (I also believe there are a small set of situations where we insert distribution for parallelization purposes as opposed to a requirement for a particular operation... we'll need to determine how those work and figure out how to express correctly in this removal pattern.) Thoughts? [1] https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/planner/physical/SubsetTransformer.java [2] https://issues.apache.org/jira/browse/CALCITE-606 [3] https://github.com/julianhyde/calcite/commit/fb203dc4b9aea89bfed839c22ae3e285044df400#diff-9494b27dde1061ef95e3853cb6222b5bR103 -- Jacques Nadeau CTO and Co-Founder, Dremio
