This PR introduces the "DISTINCT" functionality into our streaming world :)
The main issues that can still be thought about are:
1) Handling of repeating columns in output.go
2) Forcing the determinisim of StarExpressions
3) Handling of outputFields in GroupBy
This PR introduces the "DISTINCT" functionality into our streaming world :) The main issues that can still be thought about are: 1) Handling of repeating columns in output.go 2) Forcing the determinisim of StarExpressions 3) Handling of outputFields in GroupBy