Hi Rajesh,
Thanks for spending time on this.
We tried applying these patches but unfortunately it didn't help
HIVE-23485: Bound GroupByOperator stats using largest NDV among columns
HIVE-23684: Large underestimation in NDV stats when input and join cardinality
ratio is big
HIVE-20432:
Based on the plan, filtered output in map-1 had mis-estimates and also
groupby operators have large misestimates.
This is causing the number of reducers to be estimated as "4" which is less
for this query. Due to the partition factor of tez, it ends up with 8
reducer slots at runtime for hive
