92 lines
2.7 KiB
Rust
92 lines
2.7 KiB
Rust
use crate::dataframe::values::{Column, NuDataFrame, NuExpression, NuLazyFrame};
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use nu_engine::CallExt;
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use nu_protocol::{
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ast::Call,
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engine::{Command, EngineState, Stack},
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Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
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};
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use polars::prelude::Expr;
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#[derive(Clone)]
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pub struct LazySelect;
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impl Command for LazySelect {
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fn name(&self) -> &str {
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"select"
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}
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fn usage(&self) -> &str {
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"Selects columns from lazyframe"
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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(
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"select expressions",
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SyntaxShape::Any,
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"Expression(s) that define the column selection",
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)
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.input_type(Type::Custom("dataframe".into()))
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.output_type(Type::Custom("dataframe".into()))
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.category(Category::Custom("lazyframe".into()))
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}
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fn examples(&self) -> Vec<Example> {
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vec![Example {
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description: "Select a column from the dataframe",
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example: "[[a b]; [6 2] [4 2] [2 2]] | into df | select a",
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result: Some(
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NuDataFrame::try_from_columns(vec![Column::new(
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"a".to_string(),
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vec![Value::test_int(6), Value::test_int(4), Value::test_int(2)],
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)])
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.expect("simple df for test should not fail")
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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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fn run(
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&self,
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engine_state: &EngineState,
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stack: &mut Stack,
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call: &Call,
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input: PipelineData,
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) -> Result<PipelineData, ShellError> {
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let vals: Vec<Value> = call.rest(engine_state, stack, 0)?;
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let value = Value::List {
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vals,
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span: call.head,
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};
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let expressions = NuExpression::extract_exprs(value)?;
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if expressions
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.iter()
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.any(|expr| !matches!(expr, Expr::Column(..)))
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{
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let value: Value = call.req(engine_state, stack, 0)?;
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return Err(ShellError::IncompatibleParametersSingle(
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"Expected only Col expressions".into(),
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value.span()?,
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));
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}
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let lazy = NuLazyFrame::try_from_pipeline(input, call.head)?;
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let lazy = NuLazyFrame::new(lazy.from_eager, lazy.into_polars().select(&expressions));
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Ok(PipelineData::Value(lazy.into_value(call.head)?, None))
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}
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}
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#[cfg(test)]
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mod test {
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use super::super::super::test_dataframe::test_dataframe;
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use super::*;
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#[test]
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fn test_examples() {
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test_dataframe(vec![Box::new(LazySelect {})])
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}
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}
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