Struct polars_io::parquet::ParquetReader

pub struct ParquetReader<R: Read + Seek> { /* private fields */ }

Available on crate feature parquet only.

Read Apache parquet format into a DataFrame.

Implementations

impl<R: MmapBytesReader> ParquetReader<R>

pub fn _finish_with_scan_ops(
    self,
    predicate: Option<Arc<dyn PhysicalIoExpr>>,
    projection: Option<&[usize]>
) -> PolarsResult<DataFrame>

Available on crate feature lazy only.

pub fn set_low_memory(self, low_memory: bool) -> Self

Try to reduce memory pressure at the expense of performance. If setting this does not reduce memory enough, turn off parallelization.

pub fn read_parallel(self, parallel: ParallelStrategy) -> Self

Read the parquet file in parallel (default). The single threaded reader consumes less memory.

pub fn with_n_rows(self, num_rows: Option<usize>) -> Self

Stop parsing when n rows are parsed. By settings this parameter the csv will be parsed sequentially.

pub fn with_columns(self, columns: Option<Vec<String>>) -> Self

Columns to select/ project

pub fn with_projection(self, projection: Option<Vec<usize>>) -> Self

Set the reader’s column projection. This counts from 0, meaning that vec![0, 4] would select the 1st and 5th column.

pub fn with_row_count(self, row_count: Option<RowCount>) -> Self

Add a row_count column.

pub fn schema(&mut self) -> PolarsResult<Schema>

Schema of the file.

pub fn num_rows(&mut self) -> PolarsResult<usize>

Number of rows in the parquet file.

impl<R: MmapBytesReader + 'static> ParquetReader<R>

pub fn batched(self, chunk_size: usize) -> PolarsResult<BatchedParquetReader>

Trait Implementations

impl<R: MmapBytesReader> SerReader<R> for ParquetReader<R>

fn new(reader: R) -> Self

Create a new ParquetReader from an existing Reader.

fn set_rechunk(self, rechunk: bool) -> Self

Rechunk to a single chunk after Reading file.

fn finish(self) -> PolarsResult<DataFrame>

Take the SerReader and return a parsed DataFrame.