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Implemented polars unnest
(#14104)
# Description Provides the ability to decomes struct columns into seperate columns for each field: <img width="655" alt="Screenshot 2024-10-16 at 09 57 22" src="https://github.com/user-attachments/assets/6706bd36-8d38-4365-b58d-ba82f2d5ba9a"> # User-Facing Changes - provides a new command `polars unnest` for decomposing struct fields into separate columns.
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@ -32,6 +32,7 @@ mod sort_by_expr;
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pub mod sql_context;
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pub mod sql_expr;
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mod take;
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mod unnest;
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mod unpivot;
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mod with_column;
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use filter::LazyFilter;
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@ -109,5 +110,6 @@ pub(crate) fn data_commands() -> Vec<Box<dyn PluginCommand<Plugin = PolarsPlugin
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Box::new(LazyFilter),
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Box::new(Shift),
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Box::new(Unique),
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Box::new(unnest::UnnestDF),
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]
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}
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145
crates/nu_plugin_polars/src/dataframe/command/data/unnest.rs
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145
crates/nu_plugin_polars/src/dataframe/command/data/unnest.rs
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@ -0,0 +1,145 @@
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use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
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use nu_protocol::{
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Category, Example, LabeledError, PipelineData, ShellError, Signature, Span, SyntaxShape,
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};
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use polars::df;
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use crate::{
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values::{CustomValueSupport, NuLazyFrame, PolarsPluginObject},
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PolarsPlugin,
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};
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use crate::values::NuDataFrame;
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#[derive(Clone)]
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pub struct UnnestDF;
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impl PluginCommand for UnnestDF {
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type Plugin = PolarsPlugin;
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fn name(&self) -> &str {
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"polars unnest"
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}
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fn description(&self) -> &str {
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"Decompose struct columns into separate columns for each of their fields. The new columns will be inserted into the dataframe at the location of the struct column."
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}
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fn signature(&self) -> Signature {
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Signature::build(self.name())
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.rest("cols", SyntaxShape::String, "columns to unnest")
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.category(Category::Custom("dataframe".into()))
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}
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fn examples(&self) -> Vec<Example> {
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vec![
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Example {
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description: "Unnest a dataframe",
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example: r#"[[id person]; [1 {name: "Bob", age: 36}] [2 {name: "Betty", age: 63}]]
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| polars into-df -s {id: i64, person: {name: str, age: u8}}
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| polars unnest person
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| polars get id name age
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| polars sort-by id"#,
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result: Some(
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NuDataFrame::from(
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df!(
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"id" => [1, 2],
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"name" => ["Bob", "Betty"],
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"age" => [36, 63]
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)
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.expect("Should be able to create a simple dataframe"),
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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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Example {
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description: "Unnest a lazy dataframe",
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example: r#"[[id person]; [1 {name: "Bob", age: 36}] [2 {name: "Betty", age: 63}]]
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| polars into-df -s {id: i64, person: {name: str, age: u8}}
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| polars into-lazy
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| polars unnest person
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| polars select (polars col id) (polars col name) (polars col age)
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| polars collect
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| polars sort-by id"#,
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result: Some(
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NuDataFrame::from(
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df!(
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"id" => [1, 2],
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"name" => ["Bob", "Betty"],
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"age" => [36, 63]
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)
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.expect("Should be able to create a simple dataframe"),
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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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fn run(
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&self,
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plugin: &Self::Plugin,
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engine: &EngineInterface,
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call: &EvaluatedCall,
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input: PipelineData,
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) -> Result<PipelineData, LabeledError> {
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match PolarsPluginObject::try_from_pipeline(plugin, input, call.head)? {
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PolarsPluginObject::NuDataFrame(df) => command_eager(plugin, engine, call, df),
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PolarsPluginObject::NuLazyFrame(lazy) => command_lazy(plugin, engine, call, lazy),
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_ => Err(ShellError::GenericError {
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error: "Must be a dataframe or lazy dataframe".into(),
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msg: "".into(),
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span: Some(call.head),
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help: None,
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inner: vec![],
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}),
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}
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.map_err(LabeledError::from)
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}
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}
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fn command_eager(
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plugin: &PolarsPlugin,
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engine: &EngineInterface,
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call: &EvaluatedCall,
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df: NuDataFrame,
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) -> Result<PipelineData, ShellError> {
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let cols = call.rest::<String>(0)?;
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let polars = df.to_polars();
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let result: NuDataFrame = polars
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.unnest(cols)
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.map_err(|e| ShellError::GenericError {
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error: format!("Error unnesting dataframe: {e}"),
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msg: "".into(),
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span: Some(call.head),
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help: None,
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inner: vec![],
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})?
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.into();
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result.to_pipeline_data(plugin, engine, call.head)
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}
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fn command_lazy(
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plugin: &PolarsPlugin,
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engine: &EngineInterface,
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call: &EvaluatedCall,
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df: NuLazyFrame,
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) -> Result<PipelineData, ShellError> {
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let cols = call.rest::<String>(0)?;
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let polars = df.to_polars();
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let result: NuLazyFrame = polars.unnest(cols).into();
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result.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 crate::test::test_polars_plugin_command;
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use super::*;
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#[test]
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fn test_examples() -> Result<(), ShellError> {
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test_polars_plugin_command(&UnnestDF)
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}
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}
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