DATETIME is a type family, not a type. (Yeah, I know that some databases have a DATETIME type, but the SQL standard doesn’t.)
I don’t know all the details, but I recall that a type family is used as a shorthand for a family of closely related types that can be implicitly converted from one to the other (e.g. SMALLINT to INTEGER). And it may be used as a shorthand for the type of a function parameter where the function has several overloads. The conversion of a character literal (a constant string such as ‘1970-01-01’) to a DATE, TIME or TIMESTAMP literal such as DATE ‘1970-01-01’ might (again, I’m not sure) use its own particular mechanism, a different mechanism from the implicit conversion of say a SMALLINT to an INTEGER. If I were you I would seek out some applicable tests - there should be quite a few in SqlValidatorTest - and step through them in a debugger. Julian > On Sep 13, 2022, at 8:49 AM, Parag Jain <paragjai...@gmail.com> wrote: > > In the AbstractTypeCoercion class, I see here > <https://github.com/apache/calcite/blob/main/core/src/main/java/org/apache/calcite/sql/validate/implicit/AbstractTypeCoercion.java#L675>, > that DateTime family contains types SqlTypeFamily.DATE, SqlTypeFamily.TIME, > SqlTypeFamily.TIMESTAMP. Here > <https://github.com/apache/calcite/blob/main/core/src/main/java/org/apache/calcite/sql/validate/implicit/AbstractTypeCoercion.java#L709> > I > can see that the Char types can be cast to DateTime type. > > However, if I define a SqlFunction with an operand of > SqlTypeFamily.DATETIME type then this logic fails and implicit cast does > not work. > > As far as I understand SqlTypeFamily.DATETIME contains SqlTypeName of DATE, > TIME, TIME_WITH_LOCAL_TIME_ZONE, TIMESTAMP, TIMESTAMP_WITH_LOCAL_TIME_ZONE. > So shouldn't implicit cast work from Char to DATETIME work as well. > > Couple questions - > 1. Is the DATETIME here used to represent values in 'YYYY-MM-DD hh:mm:ss' > format or is it just a family type ? > 2. What operand type should be used to define a function which can accept > DATE and TIMESTAMP as well as values in 'YYYY-MM-DD hh:mm:ss' format ? > > Thanks
