use crate::{
PolarsPlugin,
dataframe::values::{Column, NuDataFrame, NuExpression, NuLazyFrame},
values::{CustomValueSupport, PolarsPluginType},
};
use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
use nu_protocol::{
Category, Example, LabeledError, PipelineData, Signature, Span, SyntaxShape, Value,
};
#[derive(Clone)]
pub struct LazySelect;
impl PluginCommand for LazySelect {
type Plugin = PolarsPlugin;
fn name(&self) -> &str {
"polars select"
}
fn description(&self) -> &str {
"Selects columns from lazyframe."
}
fn signature(&self) -> Signature {
Signature::build(self.name())
.rest(
"select expressions",
SyntaxShape::Any,
"Expression(s) that define the column selection.",
)
.input_output_types(vec![
(
PolarsPluginType::NuDataFrame.into(),
PolarsPluginType::NuDataFrame.into(),
),
(
PolarsPluginType::NuLazyFrame.into(),
PolarsPluginType::NuLazyFrame.into(),
),
])
.category(Category::Custom("lazyframe".into()))
}
fn examples(&self) -> Vec<Example<'_>> {
vec![
Example {
description: "Select a column from the dataframe",
example: "[[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select a",
result: Some(
NuDataFrame::try_from_columns(
vec![Column::new(
"a".to_string(),
vec![Value::test_int(6), Value::test_int(4), Value::test_int(2)],
)],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Select a column from a dataframe using a record",
example: "[[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select {c: ((polars col a) * 2)}",
result: Some(
NuDataFrame::try_from_columns(
vec![Column::new(
"c".to_string(),
vec![Value::test_int(12), Value::test_int(8), Value::test_int(4)],
)],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Select a column from a dataframe using a mix of expressions and record of expressions",
example: "[[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select a b {c: ((polars col a) ** 2)}",
result: Some(
NuDataFrame::try_from_columns(
vec![
Column::new(
"a".to_string(),
vec![Value::test_int(6), Value::test_int(4), Value::test_int(2)],
),
Column::new(
"b".to_string(),
vec![Value::test_int(2), Value::test_int(2), Value::test_int(2)],
),
Column::new(
"c".to_string(),
vec![Value::test_int(36), Value::test_int(16), Value::test_int(4)],
),
],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Select all columns from a dataframe using a selector",
example: "[[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select (polars selector all)",
result: Some(
NuDataFrame::try_from_columns(
vec![
Column::new(
"a".to_string(),
vec![Value::test_int(6), Value::test_int(4), Value::test_int(2)],
),
Column::new(
"b".to_string(),
vec![Value::test_int(2), Value::test_int(2), Value::test_int(2)],
),
],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Select columns by name using a selector",
example: "[[a b c]; [1 2 3] [4 5 6]] | polars into-df | polars select (polars selector by-name a c)",
result: Some(
NuDataFrame::try_from_columns(
vec![
Column::new(
"a".to_string(),
vec![Value::test_int(1), Value::test_int(4)],
),
Column::new(
"c".to_string(),
vec![Value::test_int(3), Value::test_int(6)],
),
],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Select the first column using a selector",
example: "[[a b c]; [1 2 3] [4 5 6]] | polars into-df | polars select (polars selector first)",
result: Some(
NuDataFrame::try_from_columns(
vec![Column::new(
"a".to_string(),
vec![Value::test_int(1), Value::test_int(4)],
)],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
]
}
fn run(
&self,
plugin: &Self::Plugin,
engine: &EngineInterface,
call: &EvaluatedCall,
mut input: PipelineData,
) -> Result<PipelineData, LabeledError> {
let vals: Vec<Value> = call.rest(0)?;
let expr_value = Value::list(vals, call.head);
let expressions = NuExpression::extract_exprs(plugin, expr_value)?;
let metadata = input.take_metadata();
let pipeline_value = input.into_value(call.head)?;
let lazy = NuLazyFrame::try_from_value_coerce(plugin, &pipeline_value)?;
let lazy: NuLazyFrame = lazy.to_polars().select(&expressions).into();
lazy.to_pipeline_data(plugin, engine, call.head)
.map_err(LabeledError::from)
.map(|pd| pd.set_metadata(metadata))
}
}
#[cfg(test)]
mod test {
use crate::test::test_polars_plugin_command;
use super::*;
#[test]
fn test_examples() -> Result<(), nu_protocol::ShellError> {
test_polars_plugin_command(&LazySelect)
}
}