Major Description
Currently, `SimplifyConditionals` handles `true` and `false` to optimize branches. This issue improves `SimplifyConditionals` to take advantage of `null` conditions for `if` and `CaseWhen` expressions, too.
Before
scala> sql("SELECT IF(null, 1, 0)").explain() == Physical Plan == WholeStageCodegen : +- Project [if (null) 1 else 0 AS (IF(CAST(NULL AS BOOLEAN), 1, 0))#4] : +- INPUT +- Scan OneRowRelation[] scala> sql("select case when cast(null as boolean) then 1 else 2 end").explain() == Physical Plan == WholeStageCodegen : +- Project [CASE WHEN null THEN 1 ELSE 2 END AS CASE WHEN CAST(NULL AS BOOLEAN) THEN 1 ELSE 2 END#14] : +- INPUT +- Scan OneRowRelation[]
After
scala> sql("SELECT IF(null, 1, 0)").explain() == Physical Plan == WholeStageCodegen : +- Project [0 AS (IF(CAST(NULL AS BOOLEAN), 1, 0))#4] : +- INPUT +- Scan OneRowRelation[] scala> sql("select case when cast(null as boolean) then 1 else 2 end").explain() == Physical Plan == WholeStageCodegen : +- Project [2 AS CASE WHEN CAST(NULL AS BOOLEAN) THEN 1 ELSE 2 END#4] : +- INPUT +- Scan OneRowRelation[]
Hive
hive> select if(null,1,2); OK 2 hive> select case when cast(null as boolean) then 1 else 2 end; OK 2
