Minor Description
We should allows an operator (Physical plan or logical plan) to change verbosity in explain output.
For example, we may not want to display output=count(a)#48L in less-verbose mode.
scala> spark.sql("select count(a) from df").explain()
== Physical Plan ==
*HashAggregate(key=[], functions=[count(1)], output=[count(a)#48L])
+- Exchange SinglePartition
+- *HashAggregate(key=[], functions=[partial_count(1)], output=[count#50L])
+- LocalTableScan
