How to give type in case of type mismatch while doing union

[Anjali Shrishrimal]

Hi,

While doing union of 2 RelNodes with different types, I am getting NPE. (I am 
using calcite 1.21.0)
java.lang.NullPointerException: at index 0
                at 
com.google.common.collect.ObjectArrays.checkElementNotNull(ObjectArrays.java:225)
                at 
com.google.common.collect.ObjectArrays.checkElementsNotNull(ObjectArrays.java:215)
                at 
com.google.common.collect.ObjectArrays.checkElementsNotNull(ObjectArrays.java:209)
                at 
com.google.common.collect.ImmutableList.construct(ImmutableList.java:346)
                at 
com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:258)
                at 
org.apache.calcite.rel.type.RelDataTypeFactoryImpl.canonize(RelDataTypeFactoryImpl.java:373)
                at 
org.apache.calcite.rel.type.RelDataTypeFactoryImpl.createStructType(RelDataTypeFactoryImpl.java:155)
                at 
org.apache.calcite.rel.type.RelDataTypeFactoryImpl.createStructType(RelDataTypeFactoryImpl.java:146)
                at 
org.apache.calcite.rel.type.RelDataTypeFactory$Builder.build(RelDataTypeFactory.java:569)
                at 
org.apache.calcite.rel.type.RelDataTypeFactoryImpl.leastRestrictiveStructuredType(RelDataTypeFactoryImpl.java:257)
                at 
org.apache.calcite.sql.type.SqlTypeFactoryImpl.leastRestrictiveSqlType(SqlTypeFactoryImpl.java:285)
                at 
org.apache.calcite.sql.type.SqlTypeFactoryImpl.leastRestrictive(SqlTypeFactoryImpl.java:156)
                at 
org.apache.calcite.rel.core.SetOp.deriveRowType(SetOp.java:107)

If the column types (family types) are different, currently the derived type is 
null. Is there any way to control that?
Where can I define the type in case of mismatch ?


Thank you,
Anjali Shrishrimal