Crate udf

Expand description

A wrapper crate to make writing SQL user-defined functions (UDFs) easy

This crate provides bindings for easy creation of SQL user-defined functions in Rust. See the readme for more background information.

Usage

Using this crate is fairly simple: create a struct that will be used to share data among UDF functions (which can be zero-sized), then implement needed traits for it. BasicUdf provides function signatures for standard UDFs, and AggregateUdf provides signatures for aggregate (and window) UDFs. See the documentation there for a step-by-step guide.

use udf::prelude::*;

// Our struct that will produce a UDF of name `my_udf`
struct MyUdf {}

#[register]
impl BasicUdf for MyUdf {
    // Specify return type of this UDF to be a nullable integer
    type Returns<'a> = Option<i64>;

    // Perform initialization steps here
    fn init<'a>(
        cfg: &UdfCfg<Init>,
        args: &'a ArgList<'a, Init>
    ) -> Result<Self, String> {
        todo!();
    }

    // Create a result here
    fn process<'a>(
        &'a mut self,
        cfg: &UdfCfg<Process>,
        args: &ArgList<Process>,
        error: Option<NonZeroU8>,
    ) -> Result<Self::Returns<'a>, ProcessError> {
        todo!();
    }
}

Version Note

Because of reliance on a feature called GATs, this library requires Rust version >= 1.65 which is currently in beta. If rustup show does not show 1.65 or greater under active toolchain, you will need to update: