# OData Adapter For Apache Datafusion
## About
This is an [OData](https://www.odata.org/) API adapter for [Apache Datafusion](https://github.com/apache/arrow-datafusion) SQL engine.
OData protocol is positioned as "The SQL of REST", but is a somewhat legacy protocol used by some older systems. We wouldn't recommend using it as an integration protocol for some new project, but this adapter is useful if you *have to* integrate your Datafusion app with some existing OData-focused system.
## Quick Start
Start example:
```sh
RUST_LOG=debug cargo run --example simple_service
```
Query using [xh](https://github.com/ducaale/xh):
Service root:
```sh
xh GET 'http://localhost:50051/'
```
Metadata:
```sh
xh GET 'http://localhost:50051/$metadata'
```
Query collection:
```sh
xh GET 'http://localhost:50051/tickers.spy?$select=offset,from_symbol,to_symbol,close&$top=5'
```
## Status
This code is super raw and experimental. Very far from prod-ready. Use at your own risk.
- [x] Only support small subset of `OData 3.0`
- [x] Only supports `atom` format in responses
- [x] Service root resource
- [x] `$metadata` resource
- [x] Collection resource
- [x] `$select`
- [x] `$orderby`
- [x] `$skip`
- [x] `$top`
- [x] `$filter`
- [ ] pagination
- [x] real object IDs
- [x] Collection entry by ID (`service/collection(id)`)
- [x] Numeric IDs
- [ ] Other ID types
- [ ] Parameters
- [ ] Nested collections
- [ ] Functions
- [ ] ...