Major Description
1. Given a query
`select coalesce(null, 1, '1') from dual` will cause exception:
java.lang.RuntimeException: Could not determine return type of Coalesce for IntegerType,StringType
2. Given a query:
`select case when true then 1 else '1' end from dual` will cause exception:
java.lang.RuntimeException: Types in CASE WHEN must be the same or coercible to a common type: StringType != IntegerType
I checked the code, the main cause is the HiveTypeCoercion doesn't do implicit convert when there is a IntegerType and StringType.
Numeric types can be promoted to string type in case throw exceptions.
Since Hive will always do this. It need to be fixed.
