Struct polars_io::parquet::read::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 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 reading at num_rows rows.

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_index(self, row_index: Option<RowIndex>) -> Self

Add a row index column.

pub fn with_schema(self, schema: Option<ArrowSchemaRef>) -> Self

Set the Schema if already known. This must be exactly the same as the schema in the file itself.

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

Schema of the file.

pub fn use_statistics(self, toggle: bool) -> Self

Use statistics in the parquet to determine if pages can be skipped from reading.

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

Number of rows in the parquet file.

pub fn with_hive_partition_columns(self, columns: Option<Vec<Series>>) -> Self

pub fn get_metadata(&mut self) -> PolarsResult<&FileMetaDataRef>

pub fn with_predicate(self, predicate: Option<Arc<dyn PhysicalIoExpr>>) -> Self

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

Make sure that all columns are contiguous in memory by aggregating the chunks into a single array.

fn finish(self) -> PolarsResult<DataFrame>

Take the SerReader and return a parsed DataFrame.