This fix just handles the case where a column's cardinality is zero
however it's nullable and we have null stats to indicate there are null
values, therefore we adjust the cardinality from 0 to 1.
The cardinality of zero was especially problematic when calculating
cardinalities for multiple predicates with multiplication. The 0 would
propagate up the plan tree and result in poor plan choices such as
always using broadcast joins where shuffle would've been more optimal.
Testing:
* 26 Node TPC-DS 30TB run had better plans for Q4 and Q11
- Q4 172s -> 80s
- Q11 103s -> 77s
* CardinalityTest
* TpcdsPlannerTest
Change-Id: Iec967053b4991f8c67cde62adf003cbd3f429032
Reviewed-on: http://gerrit.cloudera.org:8080/16349
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
f4273a40fe