dr/README.md

# dr.rs

[![status-badge](https://ci.guillemborrell.es/api/badges/guillem/dr/status.svg)](https://ci.guillemborrell.es/guillem/dr) | [Download](https://git.guillemborrell.es/guillem/-/packages/generic/dr)

A toolkit to process data files (csv and parquet) using the command line, inspired by [csvkit](https://github.com/wireservice/csvkit), with blazing speed, and powered by Rust. 

You may wonder why I'm implementing this, since there's already [xsv](https://github.com/BurntSushi/xsv). There are two reasons for that:

1. This what I'm implementing to learn Rust
2. The Rust data ecosystem has evolved immensely since xsv was sarted. Now we can add things like SQL commands to filter csv files, or translate results to parquet files.

## Example

```bash
$ head wine.csv
Wine,Alcohol,Malic.acid,Ash,Acl,Mg,Phenols,Flavanoids,Nonflavanoid.phenols,Proanth,Color.int,Hue,OD,Proline
1,14.23,1.71,2.43,15.6,127,2.8,3.06,.28,2.29,5.64,1.04,3.92,1065
1,13.2,1.78,2.14,11.2,100,2.65,2.76,.26,1.28,4.38,1.05,3.4,1050
1,13.16,2.36,2.67,18.6,101,2.8,3.24,.3,2.81,5.68,1.03,3.17,1185
1,14.37,1.95,2.5,16.8,113,3.85,3.49,.24,2.18,7.8,.86,3.45,1480
1,13.24,2.59,2.87,21,118,2.8,2.69,.39,1.82,4.32,1.04,2.93,735
1,14.2,1.76,2.45,15.2,112,3.27,3.39,.34,1.97,6.75,1.05,2.85,1450
1,14.39,1.87,2.45,14.6,96,2.5,2.52,.3,1.98,5.25,1.02,3.58,1290
1,14.06,2.15,2.61,17.6,121,2.6,2.51,.31,1.25,5.05,1.06,3.58,1295
1,14.83,1.64,2.17,14,97,2.8,2.98,.29,1.98,5.2,1.08,2.85,1045

$ cat wine.csv | dr sql "select Wine, avg(Alcohol) from this group by Wine" | dr print
shape: (3, 2)
┌──────┬───────────┐
│ Wine ┆ Alcohol   │
│ ---  ┆ ---       │
│ i64  ┆ f64       │
╞══════╪═══════════╡
│ 3    ┆ 13.15375  │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
│ 1    ┆ 13.744746 │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
│ 2    ┆ 12.278732 │
└──────┴───────────┘
```

## Performance

`dr` is implemented in Rust with the goal of achieving the highest possible performance. Take for instance a simple read, groupby, and aggregate operation with ~30MB of data:

```bash
$ time cat data/walmart_train.csv | ./target/release/dr sql "select Dept, avg("Weekly_Sales") from this group by Dept" | ./target/release/dr print
shape: (81, 2)
┌──────┬──────────────┐
│ Dept ┆ Weekly_Sales │
│ ---  ┆ ---          │
│ i64  ┆ f64          │
╞══════╪══════════════╡
│ 30   ┆ 4118.197208  │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ 16   ┆ 14245.63827  │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ 56   ┆ 3833.706211  │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ 24   ┆ 6353.604562  │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ ...  ┆ ...          │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ 31   ┆ 2339.440287  │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ 59   ┆ 694.463564   │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ 27   ┆ 1583.437727  │
├╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
│ 77   ┆ 328.9618     │
└──────┴──────────────┘

real    0m0.089s
user    0m0.116s
sys     0m0.036s
```

Let's compare that with the followint Python script that leverages Pandas to read the data, and compute the aggregation:

```python
#!/usr/bin/env python3

import sys
import pandas as pd

df = pd.read_csv(sys.stdin)
print(df.groupby("Dept", sort=False, as_index=False).Weekly_Sales.mean())
```

```bash
$ time cat data/walmart_train.csv | ./python/group.py 
    Dept  Weekly_Sales
0      1  19213.485088
1      2  43607.020113
2      3  11793.698516
3      4  25974.630238
4      5  21365.583515
..   ...           ...
76    99    415.487065
77    39     11.123750
78    50   2658.897010
79    43      1.193333
80    65  45441.706224

[81 rows x 2 columns]

real    0m0.717s
user    0m0.627s
sys     0m0.282s
```

Note that there's roughly a 6x speedup. This considering that this operation in particular is heavily optimized in Pandas and most of the run time is spent in parsing and reading from stdin.


## Built standing on the shoulders of giants

None of this would be possible without [Polars](https://github.com/pola-rs/polars)