nushell/crates/nu-command/src/dataframe/eager/to_parquet.rs

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use std::{fs::File, path::PathBuf};
use nu_engine::CallExt;
use nu_protocol::{
ast::Call,
engine::{Command, EngineState, Stack},
Category, Example, PipelineData, ShellError, Signature, Spanned, SyntaxShape, Type, Value,
};
use polars::prelude::ParquetWriter;
use super::super::values::NuDataFrame;
#[derive(Clone)]
pub struct ToParquet;
impl Command for ToParquet {
fn name(&self) -> &str {
"to-parquet"
}
fn usage(&self) -> &str {
"Saves dataframe to parquet file"
}
fn signature(&self) -> Signature {
Signature::build(self.name())
.required("file", SyntaxShape::Filepath, "file path to save dataframe")
.category(Category::Custom("dataframe".into()))
}
fn examples(&self) -> Vec<Example> {
vec![Example {
description: "Saves dataframe to parquet file",
example: "[[a b]; [1 2] [3 4]] | to-df | to-parquet test.parquet",
result: None,
}]
}
fn input_type(&self) -> Type {
Type::Custom("dataframe".into())
}
fn output_type(&self) -> Type {
Type::Any
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
command(engine_state, stack, call, input)
}
}
fn command(
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let file_name: Spanned<PathBuf> = call.req(engine_state, stack, 0)?;
let mut df = NuDataFrame::try_from_pipeline(input, call.head)?;
let file = File::create(&file_name.item).map_err(|e| {
ShellError::GenericError(
"Error with file name".into(),
e.to_string(),
Some(file_name.span),
None,
Vec::new(),
)
})?;
ParquetWriter::new(file).finish(df.as_mut()).map_err(|e| {
ShellError::GenericError(
"Error saving file".into(),
e.to_string(),
Some(file_name.span),
None,
Vec::new(),
)
})?;
let file_value = Value::String {
val: format!("saved {:?}", &file_name.item),
span: file_name.span,
};
Ok(PipelineData::Value(
Value::List {
vals: vec![file_value],
span: call.head,
},
None,
))
}