Casting behavior inconsistency (hashtag2793)

[vikramsubramanian]

I notice the following inconsistency:

I cannot do the following:

kuzu> RETURN cast(false, "BOOL") as bar;
Error: Conversion exception: Unsupported casting function from BOOL to BOOL.

But I can do STRING to STRING or INT64 to INT64. For example:

kuzu> RETURN cast("123", "STRING") as bar;
-------
| bar |
-------
| 123 |
-------

)

[mayil-ai[bot]]

Summary: Inconsistency in casting behavior for certain data types in the Kuzu query language.

Possible Solution

To resolve the issue with the "Conversion exception: Unsupported casting function from BOOL to BOOL," you should:

• Add a case for LogicalTypeID::BOOL in the vector_cast_functions.cpp file that handles casting from bool to bool without changing the type. This case should be similar to the one for STRING that uses CastToString but instead should use an identity function or a no-op since the types are the same.
• Ensure that the cast function checks if the source type and the target type are the same before attempting any conversion logic, and if they are the same, it should return the input value directly.
• Add test cases to verify that casting from BOOL to BOOL works as expected without throwing an exception.

Here is a code snippet that could be added to the vector_cast_functions.cpp file:

case LogicalTypeID::BOOL: {
    func = ScalarFunction::UnaryCastExecFunction<bool, bool, CastToSame<bool>, EXECUTOR>;
} break;

And the CastToSame template function:

template<typename T>
static T CastToSame(T value) {
    return value;
}

Make sure to add this function in an appropriate location within the codebase, such as in a cast_functions.h file if it exists, or directly in the vector_cast_functions.cpp file if it's more suitable.

Code snippets to check

• src/function/vector_cast_functions.cpp

  This file contains the logic for casting between different types, which is directly related to the issue of casting inconsistency.

• src/function/cast_from_string_functions.cpp

  This file includes the functions for casting from strings, which might be relevant when investigating casting inconsistencies.

• src/include/function/cast/functions/cast_from_string_functions.h

  This header file declares functions for casting from strings, which could be relevant to the issue if the casting logic needs to be reviewed or modified.