# Apache DataFusion Optimizer
[Apache DataFusion] is an extensible query execution framework, written in Rust, that uses [Apache Arrow] as its in-memory format.
This crate contains the DataFusion logical optimizer.
Please see [Query Optimizer] in the Library User Guide for more information.
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.
[apache arrow]: https://arrow.apache.org/
[apache datafusion]: https://datafusion.apache.org/
[`datafusion`]: https://crates.io/crates/datafusion
[query optimizer]: https://datafusion.apache.org/library-user-guide/query-optimizer.html