[Feature Request]: Support user defined functions

[domingozhang]

Is there an existing issue for the same feature request?

• [X] I have checked the existing issues.

Is your feature request related to a problem?

No response

Describe the feature you'd like

CREATE FUNCTION [IF NOT EXISTS] func_name ([func_parameter[,...]]) RETURNS type routine_body

func_parameter: param_name type

type: Any valid MO data type

routine_body: Valid SQL routine statement

• Compatible with MySQL syntax
• Support all MO data types as return values
• Support all MO process control statements

DROP FUNCTION [IF EXISTS] f func_name();

Describe implementation you've considered

Update in 2024.01.15

The objective of this feature for 1.2 milestone is to gets a Python Machine Learning demo running. Anythings blocks this objective will be considered as feature or bug of UDF.

Documentation, Adoption, Use Case, Migration Strategy

No response

Additional information

No response

[fengttt]

Simple SQL UDF can simply be crafted into tree.

[domingozhang]

Regarding simple SQL UDF in 0.7, I suggest these features list, please review @fengttt

• Support all data types of MO as input parameters
• Support all data types of MO as return values
• User can define local variable during the UDF body
• Flow control statements, begin ... end is a must and other can be implemented in 0.8 or future releases
• Support expressions as input parameters

[aressu1985]

@domingozhang what about operators for data type? such as +/-/*/ to numeric type, and functions like sub_str to String type？

[domingozhang]

I suggest we support expressions as input parameters in 0.7.0

[fengttt]

1. variable and flow control structure is not part of sql udf. won't do. we will only support expression, but completely, any expression.
2. if user really need that, they should write python udf.

[fengttt]

UDF transfered to @aylei