# Quickstart: DataFusion

Run ORDER BY and ORDER BY ... LIMIT in Apache DataFusion on Kwker's sorts - one call on your SessionContext, the same SQL and the same results.

Web page: https://kwker.io/docs/?p=quickstart-datafusion - every Kwker documentation page for AI assistants: https://kwker.io/llms.txt

Speed up the sorts in your DataFusion queries. `kwker_datafusion::register` adds one rule to your `SessionContext`:
every `ORDER BY` on a single number column (with or without `LIMIT`) then runs on Kwker, and everything else stays
DataFusion's own. Your SQL and your results stay the same. About five minutes.

## Install

```toml notest
[dependencies]
datafusion = "55"
kwker-datafusion = "0.1"
tokio = { version = "1", features = ["macros", "rt-multi-thread"] }
```

## Keep your SQL

```rust notest
use datafusion::prelude::*;

#[tokio::main]
async fn main() -> datafusion::error::Result<()> {
    let ctx = kwker_datafusion::register(SessionContext::new());
    ctx.register_csv("trips", "trips.csv", CsvReadOptions::new()).await?;
    let top = ctx.sql("SELECT * FROM trips ORDER BY fare DESC LIMIT 100").await?;
    top.show().await?;
    Ok(())
}
```

`EXPLAIN` shows `KwkerSortExec` (or `KwkerMergeSortExec`, when the table has several partitions) where Kwker took the sort over.

## What Kwker takes over

- `ORDER BY` one column of `INT`, `BIGINT`, `INT UNSIGNED`, `BIGINT UNSIGNED`, `FLOAT` or `DOUBLE`, ascending or
  descending, `NULLS FIRST` or `NULLS LAST`, with or without `LIMIT`.
- Every other sort (several keys, text, dates) runs on DataFusion's own sort, unchanged.

## Notes

- The results equal DataFusion's: the same order, rows with equal keys in their input order.
- Floats follow DataFusion's order: `NaN` after every number ascending, before them descending; `-0.0` before `+0.0`.
- Kwker sorts on every core by default.

## Next steps

- [Data and analytics](https://kwker.io/docs/md/data.md): every data workflow - NumPy, tables, DuckDB, DataFusion, large files.
- [Quickstart: DuckDB](https://kwker.io/docs/md/quickstart-duckdb.md): the same speed-up inside DuckDB.