Enum LambdaParametersProgress 

pub enum LambdaParametersProgress {
    Partial(Vec<Option<Vec<FieldRef>>>),
    Complete(Vec<Vec<FieldRef>>),
}

Represents a step during the resolution of the parameters of all lambdas of a given higher-order function via HigherOrderUDFImpl::lambda_parameters. It’s valid that the fields of a given lambda changes between steps, and is up to the implementation to provide during the function evaluation the parameters that matches the fields returned at the LambdaParametersProgress::Complete step. See HigherOrderUDFImpl::lambda_parameters docs for more details

Variants

Partial(Vec<Option<Vec<FieldRef>>>)

The parameters of some lambdas are unknown due to a dependency on another lambda output field or are placeholders due to a dependency on it’s own output field. It’s perfectly valid to contain only Some’s and not a single None, representing lambdas that depends only on itself and not on others. HigherOrderUDFImpl::lambda_parameters will be called again with the output field of all lambdas with known parameters.

Complete(Vec<Vec<FieldRef>>)

There are no unmet dependencies and all parameters are known, HigherOrderUDFImpl::lambda_parameters will not be called again