Nong Li 7f08146b88 Add ndv (distinct estimate) as a builtin aggregate function. ...

This is implemented in the BE using HLL (but we could change this in the
future).

These estimates usually work better than the other algorithm we have and
we've not implemented all the improvements from the google paper.

Change-Id: Ied715ddd0e1a7cbe7f5f90469f1ed3d4b9c537c7
Reviewed-on: http://gerrit.ent.cloudera.com:8080/956
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins

2014-01-08 10:54:03 -08:00

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