Gandiva Rust UDF

This project is a collection of UDFs written in Rust for Apache Arrow Gandiva.

How to write a new UDF

1. Create a new cargo workspace, like my_func
2. Two dependencies should be added for this new workspace:
   1. gandiva_rust_udf_macro
   2. gandiva_rust_udf_shared
3. If your function accepts string parameter or returns string value, you should add libc as dependency
4. Add a new function in my_func/src/lib.rs
   1. import use gandiva_rust_udf_macro::udf
   2. use #[udf] macro to annotate this function
   3. Unit test your function
5. Add my_func as dependency in udf_core/Cargo.toml
6. Register my_func in udf_core/src/lib.rs
7. Compile udf_core as shared library
   1. cargo build --release --lib --workspace
8. Deploy libudf_core shared library to where your Gandiva application can load it

How to create a different project like this

1. udf_core

[lib]
crate-type = ["cdylib"]

1. each function MUST depends on gandiva_rust_udf_shared crate