Hello Spark, as I tried to implement an improvement on Delta Lake by changing a signature of a command by making it return some data (see https://github.com/delta-io/delta/pull/1240/files#diff-f993636fe0ceb5f15de09ed4a0a71ea405a5e89ad66d36047099fcc1387a375aR123) the code produced a runtime exception because I didn't add override the output here
https://github.com/delta-io/delta/pull/1240/files#diff-f993636fe0ceb5f15de09ed4a0a71ea405a5e89ad66d36047099fcc1387a375aR123 The loop here makes https://github.com/apache/spark/pull/37778/files about the length of two collections and uses the index of the first collection to iterate on the second as well. A more defensive approach would have been to zip the two collections or at least check if this pre-requisite is met. I understand it might not be a big problem, but if you think this is worth addressing or improving, besides the "throw a more meaningful error" approach suggested in a PR, other suitable approaches could be: - removing the default value for the output collection and forcing a clear decision from the developer upon override, providing a mixable trait "NoOutputCommand" - adding scalaDoc to org.apache.spark.sql.catalyst.plans.logical.Command#output - overwriting the default output instance in LeafCommand and making it return a ??? What do you think? Edmondo
