Trait polars::prelude::LazyFileListReader

pub trait LazyFileListReader: Clone {
    // Required methods
    fn finish_no_glob(self) -> Result<LazyFrame, PolarsError>;
    fn path(&self) -> &Path;
    fn paths(&self) -> &[PathBuf];
    fn with_path(self, path: PathBuf) -> Self;
    fn with_paths(self, paths: Arc<[PathBuf]>) -> Self;
    fn with_n_rows(self, n_rows: impl Into<Option<usize>>) -> Self;
    fn with_row_index(self, row_index: impl Into<Option<RowIndex>>) -> Self;
    fn rechunk(&self) -> bool;
    fn with_rechunk(self, toggle: bool) -> Self;
    fn n_rows(&self) -> Option<usize>;
    fn row_index(&self) -> Option<&RowIndex>;

    // Provided methods
    fn finish(self) -> Result<LazyFrame, PolarsError> { ... }
    fn concat_impl(&self, lfs: Vec<LazyFrame>) -> Result<LazyFrame, PolarsError> { ... }
    fn glob(&self) -> bool { ... }
    fn cloud_options(&self) -> Option<&CloudOptions> { ... }
    fn iter_paths(
        &self
    ) -> Result<Option<Box<dyn Iterator<Item = Result<PathBuf, PolarsError>>>>, PolarsError> { ... }
}

Available on crate feature lazy only.

Reads LazyFrame from a filesystem or a cloud storage. Supports glob patterns.

Use LazyFileListReader::finish to get the final LazyFrame.

Required Methods

fn finish_no_glob(self) -> Result<LazyFrame, PolarsError>

Get the final LazyFrame. This method assumes, that path is not a glob.

It is recommended to always use LazyFileListReader::finish method.

fn path(&self) -> &Path

Path of the scanned file. It can be potentially a glob pattern.

fn paths(&self) -> &[PathBuf]

fn with_path(self, path: PathBuf) -> Self

Set path of the scanned file. Support glob patterns.

fn with_paths(self, paths: Arc<[PathBuf]>) -> Self

Set paths of the scanned files. Doesn’t glob patterns.

fn with_n_rows(self, n_rows: impl Into<Option<usize>>) -> Self

Configure the row limit.

fn with_row_index(self, row_index: impl Into<Option<RowIndex>>) -> Self

Configure the row index.

fn rechunk(&self) -> bool

Rechunk the memory to contiguous chunks when parsing is done.

fn with_rechunk(self, toggle: bool) -> Self

Rechunk the memory to contiguous chunks when parsing is done.

fn n_rows(&self) -> Option<usize>

Try to stop parsing when n rows are parsed. During multithreaded parsing the upper bound n cannot be guaranteed.

fn row_index(&self) -> Option<&RowIndex>

Add a row index column.

Provided Methods

fn finish(self) -> Result<LazyFrame, PolarsError>

Get the final LazyFrame.

fn concat_impl(&self, lfs: Vec<LazyFrame>) -> Result<LazyFrame, PolarsError>

Recommended concatenation of LazyFrames from many input files.

This method should not take into consideration LazyFileListReader::n_rows nor LazyFileListReader::row_index.

fn glob(&self) -> bool

fn cloud_options(&self) -> Option<&CloudOptions>

CloudOptions used to list files.

fn iter_paths( &self ) -> Result<Option<Box<dyn Iterator<Item = Result<PathBuf, PolarsError>>>>, PolarsError>

Get list of files referenced by this reader.

Returns None if path is not a glob pattern.

Object Safety

This trait is not object safe.

Implementors

impl LazyFileListReader for LazyCsvReader

impl LazyFileListReader for LazyJsonLineReader