Merge `polars sink` and `polars to-*` to `polars save` (#13568)

# Description
This pull request merges `polars sink` and `polars to-*` into one
command `polars save`.


# User-Facing Changes
- `polars to-*` commands have all been replaced with `polars save`. When
saving a lazy frame to a type that supports a polars sink operation, a
sink operation will be performed. Sink operations are much more
performant, performing a collect while streaming to the file system.

17 files changed, 795 insertions, 1008 deletions

diff --git a/crates/nu_plugin_polars/src/dataframe/eager/mod.rs b/crates/nu_plugin_polars/src/dataframe/eager/mod.rs
index 6aa37d1ed..1dea968ef 100644
--- a/crates/nu_plugin_polars/src/dataframe/eager/mod.rs
+++ b/crates/nu_plugin_polars/src/dataframe/eager/mod.rs
@@ -14,6 +14,7 @@ mod pivot;
 mod query_df;
 mod rename;
 mod sample;
+mod save;
 mod schema;
 mod shape;
 mod slice;
@@ -21,13 +22,8 @@ mod sql_context;
 mod sql_expr;
 mod summary;
 mod take;
-mod to_arrow;
-mod to_avro;
-mod to_csv;
 mod to_df;
-mod to_json_lines;
 mod to_nu;
-mod to_parquet;
 mod unpivot;
 mod with_column;
 
@@ -55,13 +51,8 @@ pub use slice::SliceDF;
 pub use sql_context::SQLContext;
 pub use summary::Summary;
 pub use take::TakeDF;
-pub use to_arrow::ToArrow;
-pub use to_avro::ToAvro;
-pub use to_csv::ToCSV;
 pub use to_df::ToDataFrame;
-pub use to_json_lines::ToJsonLines;
 pub use to_nu::ToNu;
-pub use to_parquet::ToParquet;
 pub use unpivot::UnpivotDF;
 pub use with_column::WithColumn;
 
@@ -89,13 +80,9 @@ pub(crate) fn eager_commands() -> Vec<Box<dyn PluginCommand<Plugin = PolarsPlugi
         Box::new(SchemaCmd),
         Box::new(TakeDF),
         Box::new(ToNu),
-        Box::new(ToArrow),
-        Box::new(ToAvro),
         Box::new(ToDataFrame),
-        Box::new(ToCSV),
-        Box::new(ToJsonLines),
-        Box::new(ToParquet),
         Box::new(QueryDf),
         Box::new(WithColumn),
+        Box::new(save::SaveDF),
     ]
 }
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/open.rs b/crates/nu_plugin_polars/src/dataframe/eager/open.rs
index 6c4246497..77fbe583a 100644
--- a/crates/nu_plugin_polars/src/dataframe/eager/open.rs
+++ b/crates/nu_plugin_polars/src/dataframe/eager/open.rs
@@ -1,6 +1,6 @@
 use crate::{
     dataframe::values::NuSchema,
-    values::{CustomValueSupport, NuLazyFrame},
+    values::{CustomValueSupport, NuLazyFrame, PolarsFileType},
     EngineWrapper, PolarsPlugin,
 };
 use nu_path::expand_path_with;
@@ -46,7 +46,7 @@ impl PluginCommand for OpenDataFrame {
     }
 
     fn usage(&self) -> &str {
-        "Opens CSV, JSON, JSON lines, arrow, avro, or parquet file to create dataframe. A lazy dataframe will be created by default, if supported."
+        "Opens CSV, JSON, NDJSON/JSON lines, arrow, avro, or parquet file to create dataframe. A lazy dataframe will be created by default, if supported."
     }
 
     fn signature(&self) -> Signature {
@@ -130,33 +130,37 @@ fn command(
     let file_path = expand_path_with(&spanned_file.item, engine.get_current_dir()?, true);
     let file_span = spanned_file.span;
 
-    let type_option: Option<Spanned<String>> = call.get_flag("type")?;
-
-    let type_id = match &type_option {
-        Some(ref t) => Some((t.item.to_owned(), "Invalid type", t.span)),
-        None => file_path.extension().map(|e| {
-            (
-                e.to_string_lossy().into_owned(),
-                "Invalid extension",
-                spanned_file.span,
-            )
-        }),
-    };
-
-    match type_id {
-        Some((e, msg, blamed)) => match e.as_str() {
-            "csv" | "tsv" => from_csv(plugin, engine, call, &file_path, file_span),
-            "parquet" | "parq" => from_parquet(plugin, engine, call, &file_path, file_span),
-            "ipc" | "arrow" => from_ipc(plugin, engine, call, &file_path, file_span),
-            "json" => from_json(plugin, engine, call, &file_path, file_span),
-            "jsonl" => from_jsonl(plugin, engine, call, &file_path, file_span),
-            "avro" => from_avro(plugin, engine, call, &file_path, file_span),
-            _ => Err(ShellError::FileNotFoundCustom {
-                msg: format!(
-                    "{msg}. Supported values: csv, tsv, parquet, ipc, arrow, json, jsonl, avro"
-                ),
-                span: blamed,
-            }),
+    let type_option: Option<(String, Span)> = call
+        .get_flag("type")?
+        .map(|t: Spanned<String>| (t.item, t.span))
+        .or_else(|| {
+            file_path
+                .extension()
+                .map(|e| (e.to_string_lossy().into_owned(), spanned_file.span))
+        });
+
+    match type_option {
+        Some((ext, blamed)) => match PolarsFileType::from(ext.as_str()) {
+            PolarsFileType::Csv | PolarsFileType::Tsv => {
+                from_csv(plugin, engine, call, &file_path, file_span)
+            }
+            PolarsFileType::Parquet => from_parquet(plugin, engine, call, &file_path, file_span),
+            PolarsFileType::Arrow => from_arrow(plugin, engine, call, &file_path, file_span),
+            PolarsFileType::Json => from_json(plugin, engine, call, &file_path, file_span),
+            PolarsFileType::NdJson => from_ndjson(plugin, engine, call, &file_path, file_span),
+            PolarsFileType::Avro => from_avro(plugin, engine, call, &file_path, file_span),
+            _ => Err(PolarsFileType::build_unsupported_error(
+                &ext,
+                &[
+                    PolarsFileType::Csv,
+                    PolarsFileType::Tsv,
+                    PolarsFileType::Parquet,
+                    PolarsFileType::Arrow,
+                    PolarsFileType::NdJson,
+                    PolarsFileType::Avro,
+                ],
+                blamed,
+            )),
         },
         None => Err(ShellError::FileNotFoundCustom {
             msg: "File without extension".into(),
@@ -268,7 +272,7 @@ fn from_avro(
     df.cache_and_to_value(plugin, engine, call.head)
 }
 
-fn from_ipc(
+fn from_arrow(
     plugin: &PolarsPlugin,
     engine: &nu_plugin::EngineInterface,
     call: &nu_plugin::EvaluatedCall,
@@ -370,7 +374,7 @@ fn from_json(
     df.cache_and_to_value(plugin, engine, call.head)
 }
 
-fn from_jsonl(
+fn from_ndjson(
     plugin: &PolarsPlugin,
     engine: &nu_plugin::EngineInterface,
     call: &nu_plugin::EvaluatedCall,
@@ -397,18 +401,14 @@ fn from_jsonl(
             .with_schema(maybe_schema.map(|s| s.into()))
             .finish()
             .map_err(|e| ShellError::GenericError {
-                error: format!("Json lines reader error: {e}"),
+                error: format!("NDJSON reader error: {e}"),
                 msg: "".into(),
                 span: Some(call.head),
                 help: None,
                 inner: vec![],
             })?;
 
-        perf!(
-            "Lazy json lines dataframe open",
-            start_time,
-            engine.use_color()
-        );
+        perf!("Lazy NDJSON dataframe open", start_time, engine.use_color());
 
         let df = NuLazyFrame::new(false, df);
         df.cache_and_to_value(plugin, engine, call.head)
@@ -444,7 +444,7 @@ fn from_jsonl(
             .into();
 
         perf!(
-            "Eager json lines dataframe open",
+            "Eager NDJSON dataframe open",
             start_time,
             engine.use_color()
         );
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/save/arrow.rs b/crates/nu_plugin_polars/src/dataframe/eager/save/arrow.rs
new file mode 100644
index 000000000..2c972c4d4
--- /dev/null
+++ b/crates/nu_plugin_polars/src/dataframe/eager/save/arrow.rs
@@ -0,0 +1,62 @@
+use std::{fs::File, path::Path};
+
+use nu_plugin::EvaluatedCall;
+use nu_protocol::{ShellError, Span};
+use polars::prelude::{IpcWriter, SerWriter};
+use polars_io::ipc::IpcWriterOptions;
+
+use crate::values::{NuDataFrame, NuLazyFrame};
+
+use super::polars_file_save_error;
+
+pub(crate) fn command_lazy(
+    _call: &EvaluatedCall,
+    lazy: &NuLazyFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    lazy.to_polars()
+        .sink_ipc(file_path, IpcWriterOptions::default())
+        .map_err(|e| polars_file_save_error(e, file_span))
+}
+
+pub(crate) fn command_eager(
+    df: &NuDataFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    let mut file = File::create(file_path).map_err(|e| ShellError::GenericError {
+        error: format!("Error with file name: {e}"),
+        msg: "".into(),
+        span: Some(file_span),
+        help: None,
+        inner: vec![],
+    })?;
+
+    IpcWriter::new(&mut file)
+        .finish(&mut df.to_polars())
+        .map_err(|e| ShellError::GenericError {
+            error: "Error saving file".into(),
+            msg: e.to_string(),
+            span: Some(file_span),
+            help: None,
+            inner: vec![],
+        })?;
+    Ok(())
+}
+
+#[cfg(test)]
+pub mod test {
+
+    use crate::eager::save::test::{test_eager_save, test_lazy_save};
+
+    #[test]
+    pub fn test_arrow_eager_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_eager_save("arrow")
+    }
+
+    #[test]
+    pub fn test_arrow_lazy_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_lazy_save("arrow")
+    }
+}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/save/avro.rs b/crates/nu_plugin_polars/src/dataframe/eager/save/avro.rs
new file mode 100644
index 000000000..58463ec36
--- /dev/null
+++ b/crates/nu_plugin_polars/src/dataframe/eager/save/avro.rs
@@ -0,0 +1,74 @@
+use std::fs::File;
+use std::path::Path;
+
+use nu_plugin::EvaluatedCall;
+use nu_protocol::{ShellError, Span};
+use polars_io::avro::{AvroCompression, AvroWriter};
+use polars_io::SerWriter;
+
+use crate::values::NuDataFrame;
+
+fn get_compression(call: &EvaluatedCall) -> Result<Option<AvroCompression>, ShellError> {
+    if let Some((compression, span)) = call
+        .get_flag_value("avro-compression")
+        .map(|e| e.as_str().map(|s| (s.to_owned(), e.span())))
+        .transpose()?
+    {
+        match compression.as_ref() {
+            "snappy" => Ok(Some(AvroCompression::Snappy)),
+            "deflate" => Ok(Some(AvroCompression::Deflate)),
+            _ => Err(ShellError::IncorrectValue {
+                msg: "compression must be one of deflate or snappy".to_string(),
+                val_span: span,
+                call_span: span,
+            }),
+        }
+    } else {
+        Ok(None)
+    }
+}
+
+pub(crate) fn command_eager(
+    call: &EvaluatedCall,
+    df: &NuDataFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    let compression = get_compression(call)?;
+
+    let file = File::create(file_path).map_err(|e| ShellError::GenericError {
+        error: format!("Error with file name: {e}"),
+        msg: "".into(),
+        span: Some(file_span),
+        help: None,
+        inner: vec![],
+    })?;
+
+    AvroWriter::new(file)
+        .with_compression(compression)
+        .finish(&mut df.to_polars())
+        .map_err(|e| ShellError::GenericError {
+            error: "Error saving file".into(),
+            msg: e.to_string(),
+            span: Some(file_span),
+            help: None,
+            inner: vec![],
+        })?;
+
+    Ok(())
+}
+
+#[cfg(test)]
+pub mod test {
+    use crate::eager::save::test::{test_eager_save, test_lazy_save};
+
+    #[test]
+    pub fn test_avro_eager_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_eager_save("avro")
+    }
+
+    #[test]
+    pub fn test_avro_lazy_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_lazy_save("avro")
+    }
+}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/save/csv.rs b/crates/nu_plugin_polars/src/dataframe/eager/save/csv.rs
new file mode 100644
index 000000000..f43b1b023
--- /dev/null
+++ b/crates/nu_plugin_polars/src/dataframe/eager/save/csv.rs
@@ -0,0 +1,111 @@
+use std::{fs::File, path::Path};
+
+use nu_plugin::EvaluatedCall;
+use nu_protocol::{ShellError, Span, Spanned};
+use polars::prelude::{CsvWriter, SerWriter};
+use polars_io::csv::write::{CsvWriterOptions, SerializeOptions};
+
+use crate::values::{NuDataFrame, NuLazyFrame};
+
+use super::polars_file_save_error;
+
+pub(crate) fn command_lazy(
+    call: &EvaluatedCall,
+    lazy: &NuLazyFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    let delimiter: Option<Spanned<String>> = call.get_flag("csv-delimiter")?;
+    let separator = delimiter
+        .and_then(|d| d.item.chars().next().map(|c| c as u8))
+        .unwrap_or(b',');
+
+    let no_header: bool = call.has_flag("csv-no-header")?;
+
+    let options = CsvWriterOptions {
+        include_header: !no_header,
+        serialize_options: SerializeOptions {
+            separator,
+            ..SerializeOptions::default()
+        },
+        ..CsvWriterOptions::default()
+    };
+
+    lazy.to_polars()
+        .sink_csv(file_path, options)
+        .map_err(|e| polars_file_save_error(e, file_span))
+}
+
+pub(crate) fn command_eager(
+    call: &EvaluatedCall,
+    df: &NuDataFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    let delimiter: Option<Spanned<String>> = call.get_flag("csv-delimiter")?;
+    let no_header: bool = call.has_flag("csv-no-header")?;
+
+    let mut file = File::create(file_path).map_err(|e| ShellError::GenericError {
+        error: format!("Error with file name: {e}"),
+        msg: "".into(),
+        span: Some(file_span),
+        help: None,
+        inner: vec![],
+    })?;
+
+    let writer = CsvWriter::new(&mut file);
+
+    let writer = if no_header {
+        writer.include_header(false)
+    } else {
+        writer.include_header(true)
+    };
+
+    let mut writer = match delimiter {
+        None => writer,
+        Some(d) => {
+            if d.item.len() != 1 {
+                return Err(ShellError::GenericError {
+                    error: "Incorrect delimiter".into(),
+                    msg: "Delimiter has to be one char".into(),
+                    span: Some(d.span),
+                    help: None,
+                    inner: vec![],
+                });
+            } else {
+                let delimiter = match d.item.chars().next() {
+                    Some(d) => d as u8,
+                    None => unreachable!(),
+                };
+
+                writer.with_separator(delimiter)
+            }
+        }
+    };
+
+    writer
+        .finish(&mut df.to_polars())
+        .map_err(|e| ShellError::GenericError {
+            error: format!("Error writing to file: {e}"),
+            msg: e.to_string(),
+            span: Some(file_span),
+            help: None,
+            inner: vec![],
+        })?;
+    Ok(())
+}
+
+#[cfg(test)]
+pub mod test {
+    use crate::eager::save::test::{test_eager_save, test_lazy_save};
+
+    #[test]
+    pub fn test_csv_eager_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_eager_save("csv")
+    }
+
+    #[test]
+    pub fn test_csv_lazy_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_lazy_save("csv")
+    }
+}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/save/mod.rs b/crates/nu_plugin_polars/src/dataframe/eager/save/mod.rs
new file mode 100644
index 000000000..ce49fc54d
--- /dev/null
+++ b/crates/nu_plugin_polars/src/dataframe/eager/save/mod.rs
@@ -0,0 +1,308 @@
+mod arrow;
+mod avro;
+mod csv;
+mod ndjson;
+mod parquet;
+
+use std::path::PathBuf;
+
+use crate::{
+    values::{cant_convert_err, PolarsFileType, PolarsPluginObject, PolarsPluginType},
+    PolarsPlugin,
+};
+
+use nu_path::expand_path_with;
+use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
+use nu_protocol::{
+    Category, Example, LabeledError, PipelineData, ShellError, Signature, Span, Spanned,
+    SyntaxShape, Type, Value,
+};
+use polars::error::PolarsError;
+
+#[derive(Clone)]
+pub struct SaveDF;
+
+impl PluginCommand for SaveDF {
+    type Plugin = PolarsPlugin;
+
+    fn name(&self) -> &str {
+        "polars save"
+    }
+
+    fn usage(&self) -> &str {
+        "Saves a dataframe to disk. For lazy dataframes a sink operation will be used if the file type supports it (parquet, ipc/arrow, csv, and ndjson)."
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .required("path", SyntaxShape::Filepath, "Path to write to.")
+            .named(
+                "type",
+                SyntaxShape::String,
+                "File type: csv, json, parquet, arrow/ipc. If omitted, derive from file extension",
+                Some('t'),
+            )
+            .named(
+                "avro-compression",
+                SyntaxShape::String,
+                "Compression for avro supports deflate or snappy",
+                None,
+            )
+            .named(
+                "csv-delimiter",
+                SyntaxShape::String,
+                "file delimiter character",
+                None,
+            )
+            .switch(
+                "csv-no-header",
+                "Indicates to exclude a header row for CSV files.",
+                None,
+            )
+            .input_output_type(Type::Any, Type::String)
+            .category(Category::Custom("lazyframe".into()))
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description:
+                    "Performs a streaming collect and save the output to the specified file",
+                example: "[[a b];[1 2] [3 4]] | polars into-lazy | polars save test.parquet",
+                result: None,
+            },
+            Example {
+                description: "Saves dataframe to parquet file",
+                example: "[[a b]; [1 2] [3 4]] | polars into-df | polars save test.parquet",
+                result: None,
+            },
+            Example {
+                description: "Saves dataframe to arrow file",
+                example: "[[a b]; [1 2] [3 4]] | polars into-df | polars save test.arrow",
+                result: None,
+            },
+            Example {
+                description: "Saves dataframe to NDJSON file",
+                example: "[[a b]; [1 2] [3 4]] | polars into-df | polars save test.ndjson",
+                result: None,
+            },
+            Example {
+                description: "Saves dataframe to avro file",
+                example: "[[a b]; [1 2] [3 4]] | polars into-df | polars save test.avro",
+                result: None,
+            },
+            Example {
+                description: "Saves dataframe to CSV file",
+                example: "[[a b]; [1 2] [3 4]] | dfr into-df | dfr save test.csv",
+                result: None,
+            },
+            Example {
+                description: "Saves dataframe to CSV file using other delimiter",
+                example: "[[a b]; [1 2] [3 4]] | dfr into-df | dfr save test.csv --delimiter '|'",
+                result: None,
+            },
+        ]
+    }
+
+    fn run(
+        &self,
+        plugin: &Self::Plugin,
+        engine: &EngineInterface,
+        call: &EvaluatedCall,
+        input: PipelineData,
+    ) -> Result<PipelineData, LabeledError> {
+        let value = input.into_value(call.head)?;
+
+        match PolarsPluginObject::try_from_value(plugin, &value)? {
+            po @ PolarsPluginObject::NuDataFrame(_) | po @ PolarsPluginObject::NuLazyFrame(_) => {
+                command(plugin, engine, call, po)
+            }
+            _ => Err(cant_convert_err(
+                &value,
+                &[PolarsPluginType::NuDataFrame, PolarsPluginType::NuLazyFrame],
+            )),
+        }
+        .map_err(LabeledError::from)
+    }
+}
+
+fn command(
+    _plugin: &PolarsPlugin,
+    engine: &EngineInterface,
+    call: &EvaluatedCall,
+    polars_object: PolarsPluginObject,
+) -> Result<PipelineData, ShellError> {
+    let spanned_file: Spanned<PathBuf> = call.req(0)?;
+    let file_path = expand_path_with(&spanned_file.item, engine.get_current_dir()?, true);
+    let file_span = spanned_file.span;
+    let type_option: Option<(String, Span)> = call
+        .get_flag("type")?
+        .map(|t: Spanned<String>| (t.item, t.span))
+        .or_else(|| {
+            file_path
+                .extension()
+                .map(|e| (e.to_string_lossy().into_owned(), spanned_file.span))
+        });
+
+    match type_option {
+        Some((ext, blamed)) => match PolarsFileType::from(ext.as_str()) {
+            PolarsFileType::Parquet => match polars_object {
+                PolarsPluginObject::NuLazyFrame(ref lazy) => {
+                    parquet::command_lazy(call, lazy, &file_path, file_span)
+                }
+                PolarsPluginObject::NuDataFrame(ref df) => {
+                    parquet::command_eager(df, &file_path, file_span)
+                }
+                _ => Err(unknown_file_save_error(file_span)),
+            },
+            PolarsFileType::Arrow => match polars_object {
+                PolarsPluginObject::NuLazyFrame(ref lazy) => {
+                    arrow::command_lazy(call, lazy, &file_path, file_span)
+                }
+                PolarsPluginObject::NuDataFrame(ref df) => {
+                    arrow::command_eager(df, &file_path, file_span)
+                }
+                _ => Err(unknown_file_save_error(file_span)),
+            },
+            PolarsFileType::NdJson => match polars_object {
+                PolarsPluginObject::NuLazyFrame(ref lazy) => {
+                    ndjson::command_lazy(call, lazy, &file_path, file_span)
+                }
+                PolarsPluginObject::NuDataFrame(ref df) => {
+                    ndjson::command_eager(df, &file_path, file_span)
+                }
+                _ => Err(unknown_file_save_error(file_span)),
+            },
+            PolarsFileType::Avro => match polars_object {
+                PolarsPluginObject::NuLazyFrame(lazy) => {
+                    let df = lazy.collect(call.head)?;
+                    avro::command_eager(call, &df, &file_path, file_span)
+                }
+                PolarsPluginObject::NuDataFrame(ref df) => {
+                    avro::command_eager(call, df, &file_path, file_span)
+                }
+                _ => Err(unknown_file_save_error(file_span)),
+            },
+            PolarsFileType::Csv => match polars_object {
+                PolarsPluginObject::NuLazyFrame(ref lazy) => {
+                    csv::command_lazy(call, lazy, &file_path, file_span)
+                }
+                PolarsPluginObject::NuDataFrame(ref df) => {
+                    csv::command_eager(call, df, &file_path, file_span)
+                }
+                _ => Err(unknown_file_save_error(file_span)),
+            },
+            _ => Err(PolarsFileType::build_unsupported_error(
+                &ext,
+                &[
+                    PolarsFileType::Parquet,
+                    PolarsFileType::Csv,
+                    PolarsFileType::Arrow,
+                    PolarsFileType::NdJson,
+                    PolarsFileType::Avro,
+                ],
+                blamed,
+            )),
+        },
+        None => Err(ShellError::FileNotFoundCustom {
+            msg: "File without extension".into(),
+            span: spanned_file.span,
+        }),
+    }?;
+    let file_value = Value::string(format!("saved {:?}", &file_path), file_span);
+
+    Ok(PipelineData::Value(
+        Value::list(vec![file_value], call.head),
+        None,
+    ))
+}
+
+pub(crate) fn polars_file_save_error(e: PolarsError, span: Span) -> ShellError {
+    ShellError::GenericError {
+        error: format!("Error saving file: {e}"),
+        msg: "".into(),
+        span: Some(span),
+        help: None,
+        inner: vec![],
+    }
+}
+
+pub fn unknown_file_save_error(span: Span) -> ShellError {
+    ShellError::GenericError {
+        error: "Could not save file for unknown reason".into(),
+        msg: "".into(),
+        span: Some(span),
+        help: None,
+        inner: vec![],
+    }
+}
+
+#[cfg(test)]
+pub(crate) mod test {
+    use nu_plugin_test_support::PluginTest;
+    use nu_protocol::{Span, Value};
+    use uuid::Uuid;
+
+    use crate::PolarsPlugin;
+
+    fn test_save(cmd: &'static str, extension: &str) -> Result<(), Box<dyn std::error::Error>> {
+        let tmp_dir = tempfile::tempdir()?;
+        let mut tmp_file = tmp_dir.path().to_owned();
+        tmp_file.push(format!("{}.{}", Uuid::new_v4(), extension));
+        let tmp_file_str = tmp_file.to_str().expect("should be able to get file path");
+
+        let cmd = format!("{cmd} {tmp_file_str}");
+        let mut plugin_test = PluginTest::new("polars", PolarsPlugin::default().into())?;
+        plugin_test.engine_state_mut().add_env_var(
+            "PWD".to_string(),
+            Value::string(
+                tmp_dir
+                    .path()
+                    .to_str()
+                    .expect("should be able to get path")
+                    .to_owned(),
+                Span::test_data(),
+            ),
+        );
+        let pipeline_data = plugin_test.eval(&cmd)?;
+
+        assert!(tmp_file.exists());
+
+        let value = pipeline_data.into_value(Span::test_data())?;
+        let list = value.as_list()?;
+        assert_eq!(list.len(), 1);
+        let msg = list.first().expect("should have a value").as_str()?;
+        assert!(msg.contains("saved"));
+
+        Ok(())
+    }
+
+    pub fn test_lazy_save(extension: &str) -> Result<(), Box<dyn std::error::Error>> {
+        test_save(
+            "[[a b]; [1 2] [3 4]] | polars into-lazy | polars save",
+            extension,
+        )
+    }
+
+    pub fn test_eager_save(extension: &str) -> Result<(), Box<dyn std::error::Error>> {
+        test_save(
+            "[[a b]; [1 2] [3 4]] | polars into-df | polars save",
+            extension,
+        )
+    }
+
+    //     #[test]
+    //     pub fn test_to_ipc() -> Result<(), Box<dyn std::error::Error>> {
+    //         test_sink("ipc")
+    //     }
+    //
+    //     #[test]
+    //     pub fn test_to_csv() -> Result<(), Box<dyn std::error::Error>> {
+    //         test_sink("csv")
+    //     }
+    //
+    //     #[test]
+    //     pub fn test_to_json() -> Result<(), Box<dyn std::error::Error>> {
+    //         test_sink("ndjson")
+    //     }
+}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/save/ndjson.rs b/crates/nu_plugin_polars/src/dataframe/eager/save/ndjson.rs
new file mode 100644
index 000000000..784010307
--- /dev/null
+++ b/crates/nu_plugin_polars/src/dataframe/eager/save/ndjson.rs
@@ -0,0 +1,63 @@
+use std::{fs::File, io::BufWriter, path::Path};
+
+use nu_plugin::EvaluatedCall;
+use nu_protocol::{ShellError, Span};
+use polars::prelude::{JsonWriter, SerWriter};
+use polars_io::json::JsonWriterOptions;
+
+use crate::values::{NuDataFrame, NuLazyFrame};
+
+use super::polars_file_save_error;
+
+pub(crate) fn command_lazy(
+    _call: &EvaluatedCall,
+    lazy: &NuLazyFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    lazy.to_polars()
+        .sink_json(file_path, JsonWriterOptions::default())
+        .map_err(|e| polars_file_save_error(e, file_span))
+}
+
+pub(crate) fn command_eager(
+    df: &NuDataFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    let file = File::create(file_path).map_err(|e| ShellError::GenericError {
+        error: format!("Error with file name: {e}"),
+        msg: "".into(),
+        span: Some(file_span),
+        help: None,
+        inner: vec![],
+    })?;
+    let buf_writer = BufWriter::new(file);
+
+    JsonWriter::new(buf_writer)
+        .finish(&mut df.to_polars())
+        .map_err(|e| ShellError::GenericError {
+            error: "Error saving file".into(),
+            msg: e.to_string(),
+            span: Some(file_span),
+            help: None,
+            inner: vec![],
+        })?;
+
+    Ok(())
+}
+
+#[cfg(test)]
+pub mod test {
+    use crate::eager::save::test::{test_eager_save, test_lazy_save};
+
+    #[test]
+    pub fn test_arrow_eager_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_eager_save("ndjson")
+    }
+
+    #[test]
+    pub fn test_arrow_lazy_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_lazy_save("ndjson")
+    }
+}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/save/parquet.rs b/crates/nu_plugin_polars/src/dataframe/eager/save/parquet.rs
new file mode 100644
index 000000000..7200e2350
--- /dev/null
+++ b/crates/nu_plugin_polars/src/dataframe/eager/save/parquet.rs
@@ -0,0 +1,62 @@
+use std::{fs::File, path::Path};
+
+use nu_plugin::EvaluatedCall;
+use nu_protocol::{ShellError, Span};
+use polars::prelude::ParquetWriter;
+use polars_io::parquet::write::ParquetWriteOptions;
+
+use crate::values::{NuDataFrame, NuLazyFrame};
+
+use super::polars_file_save_error;
+
+pub(crate) fn command_lazy(
+    _call: &EvaluatedCall,
+    lazy: &NuLazyFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    lazy.to_polars()
+        .sink_parquet(file_path, ParquetWriteOptions::default())
+        .map_err(|e| polars_file_save_error(e, file_span))
+}
+
+pub(crate) fn command_eager(
+    df: &NuDataFrame,
+    file_path: &Path,
+    file_span: Span,
+) -> Result<(), ShellError> {
+    let file = File::create(file_path).map_err(|e| ShellError::GenericError {
+        error: "Error with file name".into(),
+        msg: e.to_string(),
+        span: Some(file_span),
+        help: None,
+        inner: vec![],
+    })?;
+    let mut polars_df = df.to_polars();
+    ParquetWriter::new(file)
+        .finish(&mut polars_df)
+        .map_err(|e| ShellError::GenericError {
+            error: "Error saving file".into(),
+            msg: e.to_string(),
+            span: Some(file_span),
+            help: None,
+            inner: vec![],
+        })?;
+    Ok(())
+}
+
+#[cfg(test)]
+pub(crate) mod test {
+
+    use crate::eager::save::test::{test_eager_save, test_lazy_save};
+
+    #[test]
+    pub fn test_parquet_eager_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_eager_save("parquet")
+    }
+
+    #[test]
+    pub fn test_parquet_lazy_save() -> Result<(), Box<dyn std::error::Error>> {
+        test_lazy_save("parquet")
+    }
+}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/to_arrow.rs b/crates/nu_plugin_polars/src/dataframe/eager/to_arrow.rs
deleted file mode 100644
index dfb331ac4..000000000
--- a/crates/nu_plugin_polars/src/dataframe/eager/to_arrow.rs
+++ /dev/null
@@ -1,134 +0,0 @@
-use std::{fs::File, path::PathBuf};
-
-use nu_path::expand_path_with;
-use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
-use nu_protocol::{
-    Category, Example, LabeledError, PipelineData, ShellError, Signature, Spanned, SyntaxShape,
-    Type, Value,
-};
-use polars::prelude::{IpcWriter, SerWriter};
-
-use crate::PolarsPlugin;
-
-use super::super::values::NuDataFrame;
-
-#[derive(Clone)]
-pub struct ToArrow;
-
-impl PluginCommand for ToArrow {
-    type Plugin = PolarsPlugin;
-
-    fn name(&self) -> &str {
-        "polars to-arrow"
-    }
-
-    fn usage(&self) -> &str {
-        "Saves dataframe to arrow file."
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build(self.name())
-            .required("file", SyntaxShape::Filepath, "file path to save dataframe")
-            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
-            .category(Category::Custom("dataframe".into()))
-    }
-
-    fn examples(&self) -> Vec<Example> {
-        vec![Example {
-            description: "Saves dataframe to arrow file",
-            example: "[[a b]; [1 2] [3 4]] | polars into-df | polars to-arrow test.arrow",
-            result: None,
-        }]
-    }
-
-    fn run(
-        &self,
-        plugin: &Self::Plugin,
-        engine: &EngineInterface,
-        call: &EvaluatedCall,
-        input: PipelineData,
-    ) -> Result<PipelineData, LabeledError> {
-        command(plugin, engine, call, input).map_err(|e| e.into())
-    }
-}
-
-fn command(
-    plugin: &PolarsPlugin,
-    engine: &EngineInterface,
-    call: &EvaluatedCall,
-    input: PipelineData,
-) -> Result<PipelineData, ShellError> {
-    let file_name: Spanned<PathBuf> = call.req(0)?;
-    let file_path = expand_path_with(&file_name.item, engine.get_current_dir()?, true);
-
-    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
-
-    let mut file = File::create(file_path).map_err(|e| ShellError::GenericError {
-        error: "Error with file name".into(),
-        msg: e.to_string(),
-        span: Some(file_name.span),
-        help: None,
-        inner: vec![],
-    })?;
-
-    IpcWriter::new(&mut file)
-        .finish(&mut df.to_polars())
-        .map_err(|e| ShellError::GenericError {
-            error: "Error saving file".into(),
-            msg: e.to_string(),
-            span: Some(file_name.span),
-            help: None,
-            inner: vec![],
-        })?;
-
-    let file_value = Value::string(format!("saved {:?}", &file_name.item), file_name.span);
-
-    Ok(PipelineData::Value(
-        Value::list(vec![file_value], call.head),
-        None,
-    ))
-}
-
-#[cfg(test)]
-pub mod test {
-    use nu_plugin_test_support::PluginTest;
-    use nu_protocol::{Span, Value};
-    use uuid::Uuid;
-
-    use crate::PolarsPlugin;
-
-    #[test]
-    pub fn test_to_arrow() -> Result<(), Box<dyn std::error::Error>> {
-        let tmp_dir = tempfile::tempdir()?;
-        let mut tmp_file = tmp_dir.path().to_owned();
-        tmp_file.push(format!("{}.arrow", Uuid::new_v4()));
-        let tmp_file_str = tmp_file.to_str().expect("should be able to get file path");
-
-        let cmd = format!(
-            "[[a b]; [1 2] [3 4]] | polars into-df | polars to-arrow {}",
-            tmp_file_str
-        );
-        let mut plugin_test = PluginTest::new("polars", PolarsPlugin::default().into())?;
-        plugin_test.engine_state_mut().add_env_var(
-            "PWD".to_string(),
-            Value::string(
-                tmp_dir
-                    .path()
-                    .to_str()
-                    .expect("should be able to get path")
-                    .to_owned(),
-                Span::test_data(),
-            ),
-        );
-        let pipeline_data = plugin_test.eval(&cmd)?;
-
-        assert!(tmp_file.exists());
-
-        let value = pipeline_data.into_value(Span::test_data())?;
-        let list = value.as_list()?;
-        assert_eq!(list.len(), 1);
-        let msg = list.first().expect("should have a value").as_str()?;
-        assert!(msg.contains("saved"));
-        Ok(())
-    }
-}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/to_avro.rs b/crates/nu_plugin_polars/src/dataframe/eager/to_avro.rs
deleted file mode 100644
index 3a5dc317e..000000000
--- a/crates/nu_plugin_polars/src/dataframe/eager/to_avro.rs
+++ /dev/null
@@ -1,163 +0,0 @@
-use std::{fs::File, path::PathBuf};
-
-use nu_path::expand_path_with;
-use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
-use nu_protocol::{
-    Category, Example, LabeledError, PipelineData, ShellError, Signature, Spanned, SyntaxShape,
-    Type, Value,
-};
-use polars_io::avro::{AvroCompression, AvroWriter};
-use polars_io::SerWriter;
-
-use crate::PolarsPlugin;
-
-use super::super::values::NuDataFrame;
-
-#[derive(Clone)]
-pub struct ToAvro;
-
-impl PluginCommand for ToAvro {
-    type Plugin = PolarsPlugin;
-
-    fn name(&self) -> &str {
-        "polars to-avro"
-    }
-
-    fn usage(&self) -> &str {
-        "Saves dataframe to avro file."
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build(self.name())
-            .named(
-                "compression",
-                SyntaxShape::String,
-                "use compression, supports deflate or snappy",
-                Some('c'),
-            )
-            .required("file", SyntaxShape::Filepath, "file path to save dataframe")
-            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
-            .category(Category::Custom("dataframe".into()))
-    }
-
-    fn examples(&self) -> Vec<Example> {
-        vec![Example {
-            description: "Saves dataframe to avro file",
-            example: "[[a b]; [1 2] [3 4]] | polars into-df | polars to-avro test.avro",
-            result: None,
-        }]
-    }
-
-    fn run(
-        &self,
-        plugin: &Self::Plugin,
-        engine: &EngineInterface,
-        call: &EvaluatedCall,
-        input: PipelineData,
-    ) -> Result<PipelineData, LabeledError> {
-        command(plugin, engine, call, input).map_err(LabeledError::from)
-    }
-}
-
-fn get_compression(call: &EvaluatedCall) -> Result<Option<AvroCompression>, ShellError> {
-    if let Some((compression, span)) = call
-        .get_flag_value("compression")
-        .map(|e| e.as_str().map(|s| (s.to_owned(), e.span())))
-        .transpose()?
-    {
-        match compression.as_ref() {
-            "snappy" => Ok(Some(AvroCompression::Snappy)),
-            "deflate" => Ok(Some(AvroCompression::Deflate)),
-            _ => Err(ShellError::IncorrectValue {
-                msg: "compression must be one of deflate or snappy".to_string(),
-                val_span: span,
-                call_span: span,
-            }),
-        }
-    } else {
-        Ok(None)
-    }
-}
-
-fn command(
-    plugin: &PolarsPlugin,
-    engine: &EngineInterface,
-    call: &EvaluatedCall,
-    input: PipelineData,
-) -> Result<PipelineData, ShellError> {
-    let file_name: Spanned<PathBuf> = call.req(0)?;
-    let file_path = expand_path_with(&file_name.item, engine.get_current_dir()?, true);
-    let compression = get_compression(call)?;
-
-    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
-
-    let file = File::create(file_path).map_err(|e| ShellError::GenericError {
-        error: "Error with file name".into(),
-        msg: e.to_string(),
-        span: Some(file_name.span),
-        help: None,
-        inner: vec![],
-    })?;
-
-    AvroWriter::new(file)
-        .with_compression(compression)
-        .finish(&mut df.to_polars())
-        .map_err(|e| ShellError::GenericError {
-            error: "Error saving file".into(),
-            msg: e.to_string(),
-            span: Some(file_name.span),
-            help: None,
-            inner: vec![],
-        })?;
-
-    let file_value = Value::string(format!("saved {:?}", &file_name.item), file_name.span);
-
-    Ok(PipelineData::Value(
-        Value::list(vec![file_value], call.head),
-        None,
-    ))
-}
-
-#[cfg(test)]
-pub mod test {
-    use nu_plugin_test_support::PluginTest;
-    use nu_protocol::{Span, Value};
-    use uuid::Uuid;
-
-    use crate::PolarsPlugin;
-
-    #[test]
-    pub fn test_to_avro() -> Result<(), Box<dyn std::error::Error>> {
-        let tmp_dir = tempfile::tempdir()?;
-        let mut tmp_file = tmp_dir.path().to_owned();
-        tmp_file.push(format!("{}.avro", Uuid::new_v4()));
-        let tmp_file_str = tmp_file.to_str().expect("should be able to get file path");
-
-        let cmd = format!(
-            "[[a b]; [1 2] [3 4]] | polars into-df | polars to-avro {}",
-            tmp_file_str
-        );
-        let mut plugin_test = PluginTest::new("polars", PolarsPlugin::default().into())?;
-        plugin_test.engine_state_mut().add_env_var(
-            "PWD".to_string(),
-            Value::string(
-                tmp_dir
-                    .path()
-                    .to_str()
-                    .expect("should be able to get path")
-                    .to_owned(),
-                Span::test_data(),
-            ),
-        );
-        let pipeline_data = plugin_test.eval(&cmd)?;
-
-        assert!(tmp_file.exists());
-
-        let value = pipeline_data.into_value(Span::test_data())?;
-        let list = value.as_list()?;
-        assert_eq!(list.len(), 1);
-        let msg = list.first().expect("should have a value").as_str()?;
-        assert!(msg.contains("saved"));
-        Ok(())
-    }
-}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/to_csv.rs b/crates/nu_plugin_polars/src/dataframe/eager/to_csv.rs
deleted file mode 100644
index d55a53f1f..000000000
--- a/crates/nu_plugin_polars/src/dataframe/eager/to_csv.rs
+++ /dev/null
@@ -1,181 +0,0 @@
-use std::{fs::File, path::PathBuf};
-
-use nu_path::expand_path_with;
-use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
-use nu_protocol::{
-    Category, Example, LabeledError, PipelineData, ShellError, Signature, Spanned, SyntaxShape,
-    Type, Value,
-};
-use polars::prelude::{CsvWriter, SerWriter};
-
-use crate::PolarsPlugin;
-
-use super::super::values::NuDataFrame;
-
-#[derive(Clone)]
-pub struct ToCSV;
-
-impl PluginCommand for ToCSV {
-    type Plugin = PolarsPlugin;
-
-    fn name(&self) -> &str {
-        "polars to-csv"
-    }
-
-    fn usage(&self) -> &str {
-        "Saves dataframe to CSV file."
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build(self.name())
-            .required("file", SyntaxShape::Filepath, "file path to save dataframe")
-            .named(
-                "delimiter",
-                SyntaxShape::String,
-                "file delimiter character",
-                Some('d'),
-            )
-            .switch("no-header", "Indicates if file doesn't have header", None)
-            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
-            .category(Category::Custom("dataframe".into()))
-    }
-
-    fn examples(&self) -> Vec<Example> {
-        vec![
-            Example {
-                description: "Saves dataframe to CSV file",
-                example: "[[a b]; [1 2] [3 4]] | dfr into-df | dfr to-csv test.csv",
-                result: None,
-            },
-            Example {
-                description: "Saves dataframe to CSV file using other delimiter",
-                example: "[[a b]; [1 2] [3 4]] | dfr into-df | dfr to-csv test.csv --delimiter '|'",
-                result: None,
-            },
-        ]
-    }
-
-    fn run(
-        &self,
-        plugin: &Self::Plugin,
-        engine: &EngineInterface,
-        call: &EvaluatedCall,
-        input: PipelineData,
-    ) -> Result<PipelineData, LabeledError> {
-        command(plugin, engine, call, input).map_err(|e| e.into())
-    }
-}
-
-fn command(
-    plugin: &PolarsPlugin,
-    engine: &EngineInterface,
-    call: &EvaluatedCall,
-    input: PipelineData,
-) -> Result<PipelineData, ShellError> {
-    let file_name: Spanned<PathBuf> = call.req(0)?;
-    let file_path = expand_path_with(&file_name.item, engine.get_current_dir()?, true);
-    let delimiter: Option<Spanned<String>> = call.get_flag("delimiter")?;
-    let no_header: bool = call.has_flag("no-header")?;
-
-    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
-
-    let mut file = File::create(file_path).map_err(|e| ShellError::GenericError {
-        error: "Error with file name".into(),
-        msg: e.to_string(),
-        span: Some(file_name.span),
-        help: None,
-        inner: vec![],
-    })?;
-
-    let writer = CsvWriter::new(&mut file);
-
-    let writer = if no_header {
-        writer.include_header(false)
-    } else {
-        writer.include_header(true)
-    };
-
-    let mut writer = match delimiter {
-        None => writer,
-        Some(d) => {
-            if d.item.len() != 1 {
-                return Err(ShellError::GenericError {
-                    error: "Incorrect delimiter".into(),
-                    msg: "Delimiter has to be one char".into(),
-                    span: Some(d.span),
-                    help: None,
-                    inner: vec![],
-                });
-            } else {
-                let delimiter = match d.item.chars().next() {
-                    Some(d) => d as u8,
-                    None => unreachable!(),
-                };
-
-                writer.with_separator(delimiter)
-            }
-        }
-    };
-
-    writer
-        .finish(&mut df.to_polars())
-        .map_err(|e| ShellError::GenericError {
-            error: "Error writing to file".into(),
-            msg: e.to_string(),
-            span: Some(file_name.span),
-            help: None,
-            inner: vec![],
-        })?;
-
-    let file_value = Value::string(format!("saved {:?}", &file_name.item), file_name.span);
-
-    Ok(PipelineData::Value(
-        Value::list(vec![file_value], call.head),
-        None,
-    ))
-}
-
-#[cfg(test)]
-pub mod test {
-    use nu_plugin_test_support::PluginTest;
-    use nu_protocol::{Span, Value};
-    use uuid::Uuid;
-
-    use crate::PolarsPlugin;
-
-    #[test]
-    pub fn test_to_csv() -> Result<(), Box<dyn std::error::Error>> {
-        let tmp_dir = tempfile::tempdir()?;
-        let mut tmp_file = tmp_dir.path().to_owned();
-        tmp_file.push(format!("{}.csv", Uuid::new_v4()));
-        let tmp_file_str = tmp_file.to_str().expect("should be able to get file path");
-
-        let cmd = format!(
-            "[[a b]; [1 2] [3 4]] | polars into-df | polars to-csv {}",
-            tmp_file_str
-        );
-        println!("cmd: {}", cmd);
-        let mut plugin_test = PluginTest::new("polars", PolarsPlugin::default().into())?;
-        plugin_test.engine_state_mut().add_env_var(
-            "PWD".to_string(),
-            Value::string(
-                tmp_dir
-                    .path()
-                    .to_str()
-                    .expect("should be able to get path")
-                    .to_owned(),
-                Span::test_data(),
-            ),
-        );
-        let pipeline_data = plugin_test.eval(&cmd)?;
-
-        assert!(tmp_file.exists());
-
-        let value = pipeline_data.into_value(Span::test_data())?;
-        let list = value.as_list()?;
-        assert_eq!(list.len(), 1);
-        let msg = list.first().expect("should have a value").as_str()?;
-        assert!(msg.contains("saved"));
-        Ok(())
-    }
-}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/to_json_lines.rs b/crates/nu_plugin_polars/src/dataframe/eager/to_json_lines.rs
deleted file mode 100644
index 88b4a61bb..000000000
--- a/crates/nu_plugin_polars/src/dataframe/eager/to_json_lines.rs
+++ /dev/null
@@ -1,135 +0,0 @@
-use std::{fs::File, io::BufWriter, path::PathBuf};
-
-use nu_path::expand_path_with;
-use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
-use nu_protocol::{
-    Category, Example, LabeledError, PipelineData, ShellError, Signature, Spanned, SyntaxShape,
-    Type, Value,
-};
-use polars::prelude::{JsonWriter, SerWriter};
-
-use crate::PolarsPlugin;
-
-use super::super::values::NuDataFrame;
-
-#[derive(Clone)]
-pub struct ToJsonLines;
-
-impl PluginCommand for ToJsonLines {
-    type Plugin = PolarsPlugin;
-
-    fn name(&self) -> &str {
-        "polars to-jsonl"
-    }
-
-    fn usage(&self) -> &str {
-        "Saves dataframe to a JSON lines file."
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build(self.name())
-            .required("file", SyntaxShape::Filepath, "file path to save dataframe")
-            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
-            .category(Category::Custom("dataframe".into()))
-    }
-
-    fn examples(&self) -> Vec<Example> {
-        vec![Example {
-            description: "Saves dataframe to JSON lines file",
-            example: "[[a b]; [1 2] [3 4]] | polars into-df | polars to-jsonl test.jsonl",
-            result: None,
-        }]
-    }
-
-    fn run(
-        &self,
-        plugin: &Self::Plugin,
-        engine: &EngineInterface,
-        call: &EvaluatedCall,
-        input: PipelineData,
-    ) -> Result<PipelineData, LabeledError> {
-        command(plugin, engine, call, input).map_err(LabeledError::from)
-    }
-}
-
-fn command(
-    plugin: &PolarsPlugin,
-    engine: &EngineInterface,
-    call: &EvaluatedCall,
-    input: PipelineData,
-) -> Result<PipelineData, ShellError> {
-    let file_name: Spanned<PathBuf> = call.req(0)?;
-    let file_path = expand_path_with(&file_name.item, engine.get_current_dir()?, true);
-
-    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
-
-    let file = File::create(file_path).map_err(|e| ShellError::GenericError {
-        error: "Error with file name".into(),
-        msg: e.to_string(),
-        span: Some(file_name.span),
-        help: None,
-        inner: vec![],
-    })?;
-    let buf_writer = BufWriter::new(file);
-
-    JsonWriter::new(buf_writer)
-        .finish(&mut df.to_polars())
-        .map_err(|e| ShellError::GenericError {
-            error: "Error saving file".into(),
-            msg: e.to_string(),
-            span: Some(file_name.span),
-            help: None,
-            inner: vec![],
-        })?;
-
-    let file_value = Value::string(format!("saved {:?}", &file_name.item), file_name.span);
-
-    Ok(PipelineData::Value(
-        Value::list(vec![file_value], call.head),
-        None,
-    ))
-}
-
-#[cfg(test)]
-pub mod test {
-    use nu_plugin_test_support::PluginTest;
-    use nu_protocol::{Span, Value};
-    use uuid::Uuid;
-
-    use crate::PolarsPlugin;
-
-    #[test]
-    pub fn test_to_jsonl() -> Result<(), Box<dyn std::error::Error>> {
-        let tmp_dir = tempfile::tempdir()?;
-        let mut tmp_file = tmp_dir.path().to_owned();
-        tmp_file.push(format!("{}.jsonl", Uuid::new_v4()));
-        let tmp_file_str = tmp_file.to_str().expect("should be able to get file path");
-
-        let cmd = format!(
-            "[[a b]; [1 2] [3 4]] | polars into-df | polars to-jsonl {}",
-            tmp_file_str
-        );
-        let mut plugin_test = PluginTest::new("polars", PolarsPlugin::default().into())?;
-        plugin_test.engine_state_mut().add_env_var(
-            "PWD".to_string(),
-            Value::string(
-                tmp_dir
-                    .path()
-                    .to_str()
-                    .expect("should be able to get path")
-                    .to_owned(),
-                Span::test_data(),
-            ),
-        );
-        let pipeline_data = plugin_test.eval(&cmd)?;
-
-        assert!(tmp_file.exists());
-
-        let value = pipeline_data.into_value(Span::test_data())?;
-        let list = value.as_list()?;
-        assert_eq!(list.len(), 1);
-        let msg = list.first().expect("should have a value").as_str()?;
-        assert!(msg.contains("saved"));
-        Ok(())
-    }
-}
diff --git a/crates/nu_plugin_polars/src/dataframe/eager/to_parquet.rs b/crates/nu_plugin_polars/src/dataframe/eager/to_parquet.rs
deleted file mode 100644
index 4a8208ae1..000000000
--- a/crates/nu_plugin_polars/src/dataframe/eager/to_parquet.rs
+++ /dev/null
@@ -1,135 +0,0 @@
-use std::{fs::File, path::PathBuf};
-
-use nu_path::expand_path_with;
-use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
-use nu_protocol::{
-    Category, Example, LabeledError, PipelineData, ShellError, Signature, Spanned, SyntaxShape,
-    Type, Value,
-};
-use polars::prelude::ParquetWriter;
-
-use crate::PolarsPlugin;
-
-use super::super::values::NuDataFrame;
-
-#[derive(Clone)]
-pub struct ToParquet;
-
-impl PluginCommand for ToParquet {
-    type Plugin = PolarsPlugin;
-
-    fn name(&self) -> &str {
-        "polars 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")
-            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
-            .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]] | polars into-df | polars to-parquet test.parquet",
-            result: None,
-        }]
-    }
-
-    fn run(
-        &self,
-        plugin: &Self::Plugin,
-        engine: &EngineInterface,
-        call: &EvaluatedCall,
-        input: PipelineData,
-    ) -> Result<PipelineData, LabeledError> {
-        command(plugin, engine, call, input).map_err(LabeledError::from)
-    }
-}
-
-fn command(
-    plugin: &PolarsPlugin,
-    engine: &EngineInterface,
-    call: &EvaluatedCall,
-    input: PipelineData,
-) -> Result<PipelineData, ShellError> {
-    let file_name: Spanned<PathBuf> = call.req(0)?;
-    let file_path = expand_path_with(&file_name.item, engine.get_current_dir()?, true);
-
-    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
-
-    let file = File::create(file_path).map_err(|e| ShellError::GenericError {
-        error: "Error with file name".into(),
-        msg: e.to_string(),
-        span: Some(file_name.span),
-        help: None,
-        inner: vec![],
-    })?;
-    let mut polars_df = df.to_polars();
-    ParquetWriter::new(file)
-        .finish(&mut polars_df)
-        .map_err(|e| ShellError::GenericError {
-            error: "Error saving file".into(),
-            msg: e.to_string(),
-            span: Some(file_name.span),
-            help: None,
-            inner: vec![],
-        })?;
-
-    let file_value = Value::string(format!("saved {:?}", &file_name.item), file_name.span);
-
-    Ok(PipelineData::Value(
-        Value::list(vec![file_value], call.head),
-        None,
-    ))
-}
-
-#[cfg(test)]
-pub mod test {
-    use nu_plugin_test_support::PluginTest;
-    use nu_protocol::{Span, Value};
-    use uuid::Uuid;
-
-    use crate::PolarsPlugin;
-
-    #[test]
-    pub fn test_to_parquet() -> Result<(), Box<dyn std::error::Error>> {
-        let tmp_dir = tempfile::tempdir()?;
-        let mut tmp_file = tmp_dir.path().to_owned();
-        tmp_file.push(format!("{}.parquet", Uuid::new_v4()));
-        let tmp_file_str = tmp_file.to_str().expect("should be able to get file path");
-
-        let cmd = format!(
-            "[[a b]; [1 2] [3 4]] | polars into-df | polars to-parquet {}",
-            tmp_file_str
-        );
-        let mut plugin_test = PluginTest::new("polars", PolarsPlugin::default().into())?;
-        plugin_test.engine_state_mut().add_env_var(
-            "PWD".to_string(),
-            Value::string(
-                tmp_dir
-                    .path()
-                    .to_str()
-                    .expect("should be able to get path")
-                    .to_owned(),
-                Span::test_data(),
-            ),
-        );
-        let pipeline_data = plugin_test.eval(&cmd)?;
-
-        assert!(tmp_file.exists());
-
-        let value = pipeline_data.into_value(Span::test_data())?;
-        let list = value.as_list()?;
-        assert_eq!(list.len(), 1);
-        let msg = list.first().expect("should have a value").as_str()?;
-        assert!(msg.contains("saved"));
-
-        Ok(())
-    }
-}
diff --git a/crates/nu_plugin_polars/src/dataframe/lazy/mod.rs b/crates/nu_plugin_polars/src/dataframe/lazy/mod.rs
index e1944e06a..e70143e6c 100644
--- a/crates/nu_plugin_polars/src/dataframe/lazy/mod.rs
+++ b/crates/nu_plugin_polars/src/dataframe/lazy/mod.rs
@@ -12,7 +12,6 @@ mod macro_commands;
 mod median;
 mod quantile;
 mod select;
-mod sink;
 mod sort_by_expr;
 mod to_lazy;
 
@@ -54,6 +53,5 @@ pub(crate) fn lazy_commands() -> Vec<Box<dyn PluginCommand<Plugin = PolarsPlugin
         Box::new(LazyQuantile),
         Box::new(ToLazyFrame),
         Box::new(ToLazyGroupBy),
-        Box::new(sink::Sink),
     ]
 }
diff --git a/crates/nu_plugin_polars/src/dataframe/lazy/sink.rs b/crates/nu_plugin_polars/src/dataframe/lazy/sink.rs
deleted file mode 100644
index 0fdf0200f..000000000
--- a/crates/nu_plugin_polars/src/dataframe/lazy/sink.rs
+++ /dev/null
@@ -1,205 +0,0 @@
-use std::path::PathBuf;
-
-use crate::{
-    values::{cant_convert_err, PolarsPluginObject, PolarsPluginType},
-    PolarsPlugin,
-};
-
-use super::super::values::NuLazyFrame;
-
-use nu_path::expand_path_with;
-use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
-use nu_protocol::{
-    Category, Example, LabeledError, PipelineData, ShellError, Signature, Span, Spanned,
-    SyntaxShape, Type, Value,
-};
-use polars::error::PolarsError;
-use polars_io::{
-    csv::write::CsvWriterOptions, ipc::IpcWriterOptions, json::JsonWriterOptions,
-    parquet::write::ParquetWriteOptions,
-};
-
-#[derive(Clone)]
-pub struct Sink;
-
-impl PluginCommand for Sink {
-    type Plugin = PolarsPlugin;
-
-    fn name(&self) -> &str {
-        "polars sink"
-    }
-
-    fn usage(&self) -> &str {
-        "Streams a collect result to a file. This is useful if the result is too large for memory. Supports parquet, ipc/arrow, csv, and json formats."
-    }
-
-    fn signature(&self) -> Signature {
-        Signature::build(self.name())
-            .required("path", SyntaxShape::Filepath, "Path to write to.")
-            .named(
-                "type",
-                SyntaxShape::String,
-                "File type: csv, json, parquet, arrow/ipc. If omitted, derive from file extension",
-                Some('t'),
-            )
-            .input_output_type(Type::Any, Type::String)
-            .category(Category::Custom("lazyframe".into()))
-    }
-
-    fn examples(&self) -> Vec<Example> {
-        vec![Example {
-            description: "Collect and save the output to the specified file",
-            example: "[[a b];[1 2] [3 4]] | polars into-lazy | polars sink /tmp/foo.parquet",
-            result: None,
-        }]
-    }
-
-    fn run(
-        &self,
-        plugin: &Self::Plugin,
-        engine: &EngineInterface,
-        call: &EvaluatedCall,
-        input: PipelineData,
-    ) -> Result<PipelineData, LabeledError> {
-        let value = input.into_value(call.head)?;
-
-        match PolarsPluginObject::try_from_value(plugin, &value)? {
-            PolarsPluginObject::NuDataFrame(df) => command(plugin, engine, call, df.lazy()),
-            PolarsPluginObject::NuLazyFrame(lazy) => command(plugin, engine, call, lazy),
-            _ => Err(cant_convert_err(
-                &value,
-                &[PolarsPluginType::NuDataFrame, PolarsPluginType::NuLazyFrame],
-            )),
-        }
-        .map_err(LabeledError::from)
-    }
-}
-
-fn command(
-    _plugin: &PolarsPlugin,
-    engine: &EngineInterface,
-    call: &EvaluatedCall,
-    lazy: NuLazyFrame,
-) -> Result<PipelineData, ShellError> {
-    let spanned_file: Spanned<PathBuf> = call.req(0)?;
-    let file_path = expand_path_with(&spanned_file.item, engine.get_current_dir()?, true);
-    let file_span = spanned_file.span;
-    let type_option: Option<Spanned<String>> = call.get_flag("type")?;
-    let type_id = match &type_option {
-        Some(ref t) => Some((t.item.to_owned(), "Invalid type", t.span)),
-        None => file_path.extension().map(|e| {
-            (
-                e.to_string_lossy().into_owned(),
-                "Invalid extension",
-                spanned_file.span,
-            )
-        }),
-    };
-
-    let polars_df = lazy.to_polars();
-
-    match type_id {
-        Some((e, msg, blamed)) => match e.as_str() {
-            "parquet" | "parq" => polars_df
-                .sink_parquet(&file_path, ParquetWriteOptions::default())
-                .map_err(|e| file_save_error(e, file_span))?,
-            "csv" => polars_df
-                .sink_csv(&file_path, CsvWriterOptions::default())
-                .map_err(|e| file_save_error(e, file_span))?,
-            "ipc" | "arrow" => polars_df
-                .sink_ipc(&file_path, IpcWriterOptions::default())
-                .map_err(|e| file_save_error(e, file_span))?,
-            "json" | "jsonl" | "ndjson" => polars_df
-                .sink_json(&file_path, JsonWriterOptions::default())
-                .map_err(|e| file_save_error(e, file_span))?,
-            _ => Err(ShellError::FileNotFoundCustom {
-                msg: format!("{msg}. Supported values: csv, tsv, parquet, ipc, arrow, json, jsonl"),
-                span: blamed,
-            })?,
-        },
-        None => Err(ShellError::FileNotFoundCustom {
-            msg: "File without extension".into(),
-            span: spanned_file.span,
-        })?,
-    };
-    let file_value = Value::string(format!("saved {:?}", &file_path), file_span);
-
-    Ok(PipelineData::Value(
-        Value::list(vec![file_value], call.head),
-        None,
-    ))
-}
-
-fn file_save_error(e: PolarsError, span: Span) -> ShellError {
-    ShellError::GenericError {
-        error: "Error saving file".into(),
-        msg: e.to_string(),
-        span: Some(span),
-        help: None,
-        inner: vec![],
-    }
-}
-
-#[cfg(test)]
-pub mod test {
-    use nu_plugin_test_support::PluginTest;
-    use nu_protocol::{Span, Value};
-    use uuid::Uuid;
-
-    use crate::PolarsPlugin;
-
-    pub fn test_sink(extension: &str) -> Result<(), Box<dyn std::error::Error>> {
-        let tmp_dir = tempfile::tempdir()?;
-        let mut tmp_file = tmp_dir.path().to_owned();
-        tmp_file.push(format!("{}.{}", Uuid::new_v4(), extension));
-        let tmp_file_str = tmp_file.to_str().expect("should be able to get file path");
-
-        let cmd = format!(
-            "[[a b]; [1 2] [3 4]] | polars into-lazy | polars sink {}",
-            tmp_file_str
-        );
-        let mut plugin_test = PluginTest::new("polars", PolarsPlugin::default().into())?;
-        plugin_test.engine_state_mut().add_env_var(
-            "PWD".to_string(),
-            Value::string(
-                tmp_dir
-                    .path()
-                    .to_str()
-                    .expect("should be able to get path")
-                    .to_owned(),
-                Span::test_data(),
-            ),
-        );
-        let pipeline_data = plugin_test.eval(&cmd)?;
-
-        assert!(tmp_file.exists());
-
-        let value = pipeline_data.into_value(Span::test_data())?;
-        let list = value.as_list()?;
-        assert_eq!(list.len(), 1);
-        let msg = list.first().expect("should have a value").as_str()?;
-        assert!(msg.contains("saved"));
-
-        Ok(())
-    }
-
-    #[test]
-    pub fn test_to_parquet() -> Result<(), Box<dyn std::error::Error>> {
-        test_sink("parquet")
-    }
-
-    #[test]
-    pub fn test_to_ipc() -> Result<(), Box<dyn std::error::Error>> {
-        test_sink("ipc")
-    }
-
-    #[test]
-    pub fn test_to_csv() -> Result<(), Box<dyn std::error::Error>> {
-        test_sink("csv")
-    }
-
-    #[test]
-    pub fn test_to_json() -> Result<(), Box<dyn std::error::Error>> {
-        test_sink("ndjson")
-    }
-}
diff --git a/crates/nu_plugin_polars/src/dataframe/values/file_type.rs b/crates/nu_plugin_polars/src/dataframe/values/file_type.rs
new file mode 100644
index 000000000..c46fcd711
--- /dev/null
+++ b/crates/nu_plugin_polars/src/dataframe/values/file_type.rs
@@ -0,0 +1,59 @@
+use nu_protocol::{ShellError, Span};
+
+pub enum PolarsFileType {
+    Csv,
+    Tsv,
+    Parquet,
+    Arrow,
+    Json,
+    Avro,
+    NdJson,
+    Unknown,
+}
+
+impl PolarsFileType {
+    pub fn build_unsupported_error(
+        extension: &str,
+        supported_types: &[PolarsFileType],
+        span: Span,
+    ) -> ShellError {
+        let type_string = supported_types
+            .iter()
+            .map(|ft| ft.to_str())
+            .collect::<Vec<&'static str>>()
+            .join(", ");
+
+        ShellError::FileNotFoundCustom {
+            msg: format!("Unsupported type {extension} expected {type_string}"),
+            span,
+        }
+    }
+
+    pub fn to_str(&self) -> &'static str {
+        match self {
+            PolarsFileType::Csv => "csv",
+            PolarsFileType::Tsv => "tsv",
+            PolarsFileType::Parquet => "parquet",
+            PolarsFileType::Arrow => "arrow",
+            PolarsFileType::Json => "json",
+            PolarsFileType::Avro => "avro",
+            PolarsFileType::NdJson => "ndjson",
+            PolarsFileType::Unknown => "unknown",
+        }
+    }
+}
+
+impl From<&str> for PolarsFileType {
+    fn from(file_type: &str) -> Self {
+        match file_type {
+            "csv" => PolarsFileType::Csv,
+            "tsv" => PolarsFileType::Tsv,
+            "parquet" | "parq" => PolarsFileType::Parquet,
+            "ipc" | "arrow" => PolarsFileType::Arrow,
+            "json" => PolarsFileType::Json,
+            "avro" => PolarsFileType::Avro,
+            "jsonl" | "ndjson" => PolarsFileType::NdJson,
+            _ => PolarsFileType::Unknown,
+        }
+    }
+}
diff --git a/crates/nu_plugin_polars/src/dataframe/values/mod.rs b/crates/nu_plugin_polars/src/dataframe/values/mod.rs
index ec59304ea..41a119cdd 100644
--- a/crates/nu_plugin_polars/src/dataframe/values/mod.rs
+++ b/crates/nu_plugin_polars/src/dataframe/values/mod.rs
@@ -1,3 +1,4 @@
+mod file_type;
 mod nu_dataframe;
 mod nu_expression;
 mod nu_lazyframe;
@@ -8,6 +9,7 @@ pub mod utils;
 
 use std::{cmp::Ordering, fmt};
 
+pub use file_type::PolarsFileType;
 pub use nu_dataframe::{Axis, Column, NuDataFrame, NuDataFrameCustomValue};
 pub use nu_expression::{NuExpression, NuExpressionCustomValue};
 pub use nu_lazyframe::{NuLazyFrame, NuLazyFrameCustomValue};
@@ -125,6 +127,20 @@ impl PolarsPluginObject {
             }
         }
     }
+
+    pub fn dataframe(&self) -> Option<&NuDataFrame> {
+        match self {
+            PolarsPluginObject::NuDataFrame(df) => Some(df),
+            _ => None,
+        }
+    }
+
+    pub fn lazyframe(&self) -> Option<&NuLazyFrame> {
+        match self {
+            PolarsPluginObject::NuLazyFrame(lf) => Some(lf),
+            _ => None,
+        }
+    }
 }
 
 #[derive(Debug, Clone)]