Aggregation's and GroupBy's

[araddon]

Implement groupby and aggregations Tasks. Just simple builtin aggregation functions (sum, avg, max)

• [ ] GroupBy
  • [x] aliasing on cols: aka "select user_id as uid from users group by user_id"
  • [ ] deterministic/sorted ordering on group by rows (currently bc map using non-determistic)
• [ ] Distinct
  • [ ] distinct inside of count: select count(distinct(field)) from users
• [x] recognize non-group by aggregates (count, sum, avg) when in select clause.
• [x] Aggregation Functions
  • [x] sum
  • [x] count
  • [x] avg
• other functions
  • [ ] max, min, avg, top, bottom