OperandTypeChecker just makes sure that arguments of known type are compatible;
another interface, SqlOperandTypeInference, infers the types of arguments of
unknown type.
Hopefully it’s now a little less mysterious.
> On Jan 12, 2024, at 11:12 AM, Mihai Budiu <mbu...@gmail.com> wrote:
>
> inference in Calcite is still mysterious to me.
> Here it infers the type of the argument of UPPER to be NULL instead of
> VARCHAR.
> That's why the result type of UPPER is also NULL.
> The fact that UPPER has an OperandTypeChecker of "OperandTypes.CHARACTER" is
> completely ignored:
>
> public static final SqlFunction UPPER =
> SqlBasicFunction.create("UPPER",
> ReturnTypes.ARG0_NULLABLE,
> OperandTypes.CHARACTER,
> SqlFunctionCategory.STRING);
>
> Mihai
> ________________________________
> From: stanilovsky evgeny <estanilovs...@gridgain.com>
> Sent: Friday, January 12, 2024 4:23 AM
> To: dev@calcite.apache.org <dev@calcite.apache.org>
> Subject: [Question] Derived type from string expression with NULL parameter
>
> Plz help me to understand is it a bug ?
> From standard:
> 6.18 <string value function>
> ...cut...
> <fold> ::= { UPPER | LOWER } <left paren> <character value expression>
> <right paren>
>
> 6)If <fold> is specified, then:
> a) The declared type of the result of <fold> is the declared type of the
> !!!<character value expression>!!!.
>
> thus i expect that return type from: SELECT UPPER(null) will be VARCHAR
> but calcite show :
> SqlValidatorTest
>
> @Test void testTypeOfUpper() {
> sql("SELECT UPPER(NULL)")
> .columnType("???");
> }
>
> Expected: is "???"
> but: was "NULL"
>
> I think it need to be fixed ?
>
> Thanks !
