Reviewed 4 of 16 files at r1, all commit messages.
Reviewable status: 4 of 16 files reviewed, 5 unresolved discussions (waiting on @sundy-li)

src/meta/app/src/principal/user_defined_function.rs line 59 at r1 (raw file):

    pub return_types: Vec<(String, DataType)>,
    pub sql: String,
}

add doc comment to important struct, and its field. The code itself does not show what the 'String' is.

Code quote:

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct UDTF {
    pub arg_types: Vec<(String, DataType)>,
    pub return_types: Vec<(String, DataType)>,
    pub sql: String,
}

src/meta/protos/proto/udf.proto line 74 at r1 (raw file):

message UDTFArg {
  string name = 1;
  DataType type = 2;

avoid using rust keyword

src/meta/proto-conv/src/udf_from_to_protobuf_impl.rs line 295 at r1 (raw file):

                Incompatible::new("UDTF.arg_types.ty can not be None".to_string())
            })?)?)
                .into();

Avoid put more than one action into one line.
Do each thing in a separate line.

Code quote:

            let ty = (&TableDataType::from_pb(arg_ty.r#type.ok_or_else(|| {
                Incompatible::new("UDTF.arg_types.ty can not be None".to_string())
            })?)?)
                .into();

src/meta/proto-conv/src/udf_from_to_protobuf_impl.rs line 327 at r1 (raw file):

                    ))
                })?
                .to_pb()?;

too large expression

Code quote:

            let arg_type = infer_schema_type(arg_type)
                .map_err(|e| {
                    Incompatible::new(format!(
                        "Convert DataType to TableDataType failed: {}",
                        e.message()
                    ))
                })?
                .to_pb()?;

src/meta/proto-conv/tests/it/v142_udtf.rs line 49 at r1 (raw file):

        definition: UDFDefinition::UDTF(UDTF {
            arg_types: vec![],
            return_types: vec![],

testing empty vector? it does not test anything at all

Code quote:

            arg_types: vec![],
            return_types: vec![],