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Allow polars first
to be used with polars group-by
(#15855)
# Description Provides functionality similar to https://docs.pola.rs/api/python/stable/reference/dataframe/api/polars.dataframe.group_by.GroupBy.first.html by allowing polars first to be used with a group by ``` > ❯ : [[a b c d]; [1 0.5 true Apple] [2 0.5 true Orange] [2 4 true Apple] [3 10 false Apple] [4 13 false Banana] [5 14 true Banana]] | polars into-df -s {a: u8, b: f32, c: bool, d: str} | polars group-by d | polars first | polars collect ╭───┬────────┬───┬───────┬───────╮ │ # │ d │ a │ b │ c │ ├───┼────────┼───┼───────┼───────┤ │ 0 │ Apple │ 1 │ 0.50 │ true │ │ 1 │ Banana │ 4 │ 13.00 │ false │ │ 2 │ Orange │ 2 │ 0.50 │ true │ ╰───┴────────┴───┴───────┴───────╯ ``` Additionally, I am setting the POLARS_ALLOW_EXTENSION to true to avoid panicking with operations using the dtype object. The conversion will fallback to object when the type cannot be determining, so this could be a common case. # User-Facing Changes - `polars first` can now be used with `polars group-by` --------- Co-authored-by: Jack Wright <jack.wright@nike.com>
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@ -1,6 +1,6 @@
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use crate::{
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PolarsPlugin,
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values::{Column, CustomValueSupport, NuLazyFrame, PolarsPluginObject},
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values::{Column, CustomValueSupport, NuLazyFrame, NuLazyGroupBy, PolarsPluginObject},
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};
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use crate::values::{NuDataFrame, NuExpression};
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@ -9,6 +9,7 @@ use nu_protocol::{
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Category, Example, LabeledError, PipelineData, ShellError, Signature, Span, SyntaxShape, Type,
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Value,
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};
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use polars::df;
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#[derive(Clone)]
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pub struct FirstDF;
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@ -87,6 +88,24 @@ impl PluginCommand for FirstDF {
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example: "polars col a | polars first",
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result: None,
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},
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Example {
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description: "Aggregate the first values in the group.",
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example: "[[a b c d]; [1 0.5 true Apple] [2 0.5 true Orange] [2 4 true Apple] [3 10 false Apple] [4 13 false Banana] [5 14 true Banana]] | polars into-df -s {a: u8, b: f32, c: bool, d: str} | polars group-by d | polars first | polars sort-by [a] | polars collect",
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result: Some(
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NuDataFrame::new(
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false,
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df!(
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"d" => &["Apple", "Orange", "Banana"],
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"a" => &[1, 2, 4],
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"b" => &[0.5, 0.5, 13.0],
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"c" => &[true, true, false],
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)
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.expect("dataframe creation should succeed"),
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)
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.into_value(Span::test_data()),
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),
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},
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]
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}
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@ -106,6 +125,9 @@ impl PluginCommand for FirstDF {
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PolarsPluginObject::NuLazyFrame(lazy) => {
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command_lazy(plugin, engine, call, lazy).map_err(|e| e.into())
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}
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PolarsPluginObject::NuLazyGroupBy(groupby) => {
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command_groupby(plugin, engine, call, groupby).map_err(|e| e.into())
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}
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_ => {
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let expr = NuExpression::try_from_value(plugin, &value)?;
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let expr: NuExpression = expr.into_polars().first().into();
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@ -146,6 +168,20 @@ fn command_lazy(
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res.to_pipeline_data(plugin, engine, call.head)
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}
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fn command_groupby(
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plugin: &PolarsPlugin,
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engine: &EngineInterface,
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call: &EvaluatedCall,
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groupby: NuLazyGroupBy,
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) -> Result<PipelineData, ShellError> {
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let rows: Option<usize> = call.opt(0)?;
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let rows = rows.unwrap_or(1);
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let res = groupby.to_polars().head(Some(rows));
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let res: NuLazyFrame = res.into();
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res.to_pipeline_data(plugin, engine, call.head)
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}
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#[cfg(test)]
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mod test {
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use super::*;
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@ -153,6 +189,10 @@ mod test {
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#[test]
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fn test_examples() -> Result<(), ShellError> {
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// // Extensions are required for the group-by functionality to work
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// unsafe {
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// std::env::set_var("POLARS_ALLOW_EXTENSION", "true");
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// }
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test_polars_plugin_command(&FirstDF)
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}
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}
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@ -4,6 +4,13 @@ use nu_plugin_polars::PolarsPlugin;
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fn main() {
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env_logger::init();
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// Set config options via environment variable
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unsafe {
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// Extensions are required for certain things like aggregates with object dtypes to work
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// correctly. It is disabled by default because of unsafe code.
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// See https://docs.rs/polars/latest/polars/#user-guide for details
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std::env::set_var("POLARS_ALLOW_EXTENSION", "true");
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}
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match PolarsPlugin::new() {
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Ok(ref plugin) => serve_plugin(plugin, MsgPackSerializer {}),
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Err(e) => {
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