[DRILL-665] Drill throw NPE or UnsupportedOperationException when case expression contains null value

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.4.0
• Assignee: Timothy Chen
• Reporter: Jinfeng Ni
• Created: 08/May/14 14:57
• Updated: 31/Jul/14 06:33
• Resolved: 28/May/14 22:15

Description

Hi Tim,

Per discussion yesterday, we found Drill will throw NPE or UnsupportedOperationException when case expression contains null value. (null value is added for the optional 'else' branch).

Q1:

select case when n_nationkey < 100 then 100 end from cp.`tpch/nation.parquet`;

java.lang.NullPointerException
org.apache.drill.exec.planner.logical.DrillOptiq$RexToDrill.visitLiteral(DrillOptiq.java:330) ~[drill-java-exec-1.0.0-m2-incubating-SNAPSHOT-rebuffed.jar:1.0.0-m2-incubating-SNAPSHOT]
......

Q2.

select case when n_nationkey < 100 then n_name end from cp.`tpch/nation.parquet`;

java.lang.UnsupportedOperationException: Unable to convert the value of null and type NULL to a Drill constant expression.
org.apache.drill.exec.planner.logical.DrillOptiq$RexToDrill.visitLiteral(DrillOptiq.java:367) ~[drill-java-exec-1.0.0-m2-incubating-SNAPSHOT-rebuffed.jar:1.0.0-m2-incubating-SNAPSHOT]
......

Our conclusion is Drill need create proper TypedNullConstant in DrillOptiq when the null value is associated with regular SQL type, or resolve to proper SQL typed null constant, in IExpressionTreeMaterializer.visitIfExpression. ( case/if expression requires all the branches return the type of value).