apache/tajo — pull request #70 by babokim (2014-07-14 04:49:34+00:00)
Title: TAJO-904: ORDER BY with a null column miss some data.

Currently Tajo ignores null value when calculates range partition range. I added a MaxValueNull flag variable in ColumnStats. If ColumnStats's max value is null, ColumnStats's max value is a non-null value and MaxValueNull flag is true. So Repartitioner calculates range cardinality with non-null value. Finally Repartitioner set null value to last range.