Do we guarantee the full-join result of keyed tables is also sorted? #7170
Description
if both tables are keyed why not the result?
Originally posted by @ben-schwen in #4370 (comment)
It sounds reasonable but requires some testing. Since we might need to fully interleave rows (think LHS has 1,3,5 and RHS has 2,4,NA), it could be that the output somehow winds up unsorted.
If we can guarantee it's sorted, we should leave the key intact inside mergepair().