Struct polars_lazy::frame::LazyJsonLineReader

pub struct LazyJsonLineReader { /* private fields */ }

Available on crate feature json only.

Implementations

impl LazyJsonLineReader

pub fn new(path: String) -> Self

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

Add a row_count column.

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

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

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

Set the number of rows to use when inferring the json schema. the default is 100 rows. Setting to None will do a full table scan, very slow.

pub fn with_schema(self, schema: Schema) -> Self

Set the JSON file’s schema

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

Reduce memory usage in expensive of performance

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

Rechunk the memory to contiguous chunks when parsing is done.

pub fn with_batch_size(self, batch_size: Option<usize>) -> Self

pub fn finish(self) -> PolarsResult<LazyFrame>

Trait Implementations

impl AnonymousScan for LazyJsonLineReader

fn scan(&self, scan_opts: AnonymousScanOptions) -> PolarsResult<DataFrame>

Creates a dataframe from the supplied function & scan options.

fn schema(&self, infer_schema_length: Option<usize>) -> PolarsResult<Schema>

function to supply the schema. Allows for an optional infer schema argument for data sources with dynamic schemas

fn allows_projection_pushdown(&self) -> bool

specify if the scan provider should allow projection pushdowns

fn allows_predicate_pushdown(&self) -> bool

specify if the scan provider should allow predicate pushdowns

fn allows_slice_pushdown(&self) -> bool

specify if the scan provider should allow slice pushdowns