# DataFusion Function Library
[DataFusion][df] is an extensible query execution framework, written in Rust, that uses Apache Arrow as its in-memory format.
This crate contains packages of function that can be used to customize the
functionality of DataFusion.
Most projects should use the [`datafusion`] crate directly, which re-exports
this module. If you are already using the [`datafusion`] crate, there is no
reason to use this crate directly in your project as well.
[df]: https://crates.io/crates/datafusion
[`datafusion`]: https://crates.io/crates/datafusion