Struct polars::prelude::ndjson::read::FileReader

pub struct FileReader<R> where
    R: BufRead,  { /* private fields */ }

This is supported on crate feature io_json only.

A FallibleStreamingIterator of NDJSON rows.

This iterator is used to read chunks of an NDJSON in batches. This iterator is guaranteed to yield at least one row.

Implementantion

Advancing this iterator is IO-bounded, but does require parsing each byte to find end of lines.

Error

Advancing this iterator errors iff the reader errors.

Implementations

impl<R> FileReader<R> where
    R: BufRead, 

pub fn new(
    reader: R,
    rows: Vec<String, Global>,
    limit: Option<usize>
) -> FileReader<R>

Creates a new FileReader from a reader and rows.

The number of items in rows denotes the batch size.

pub fn into_inner(self) -> (R, Vec<String, Global>)

Deconstruct FileReader into the reader and the internal buffer.

Trait Implementations

impl<R> FallibleStreamingIterator for FileReader<R> where
    R: BufRead, 

type Error = ArrowError

The error type of iteration.

type Item = [String]

The type being iterated over.

fn advance(&mut self) -> Result<(), ArrowError>

Advances the iterator to the next position.

fn get(&self) -> Option<&<FileReader<R> as FallibleStreamingIterator>::Item>

Returns the current element.

fn next(&mut self) -> Result<Option<&Self::Item>, Self::Error>

Advances the iterator, returning the next element.

fn size_hint(&self) -> (usize, Option<usize>)

Returns bounds on the number of remaining elements in the iterator.

fn all<F>(&mut self, f: F) -> Result<bool, Self::Error> where
    F: FnMut(&Self::Item) -> bool, 

Determines if all elements of the iterator satisfy a predicate.

fn any<F>(&mut self, f: F) -> Result<bool, Self::Error> where
    F: FnMut(&Self::Item) -> bool, 

Determines if any elements of the iterator satisfy a predicate.

fn by_ref(&mut self) -> &mut Self

Borrows an iterator, rather than consuming it.

fn count(self) -> Result<usize, Self::Error>

Returns the number of remaining elements in the iterator.

fn filter<F>(self, f: F) -> Filter<Self, F> where
    F: FnMut(&Self::Item) -> bool, 

Returns an iterator which filters elements by a predicate.

fn find<F>(&mut self, f: F) -> Result<Option<&Self::Item>, Self::Error> where
    F: FnMut(&Self::Item) -> bool, 

Returns the first element of the iterator which satisfies a predicate.

fn for_each<F>(self, f: F) -> Result<(), Self::Error> where
    F: FnMut(&Self::Item), 

Calls a closure on each element of an iterator.

fn fuse(self) -> Fuse<Self>

Returns an iterator which is well-behaved at the beginning and end of iteration.

fn map<F, B>(self, f: F) -> Map<Self, F, B> where
    F: FnMut(&Self::Item) -> B, 

Returns an iterator which applies a transform to elements.

fn map_ref<F, B>(self, f: F) -> MapRef<Self, F> where
    F: Fn(&Self::Item) -> &B,
    B: ?Sized, 

Returns an iterator which applies a transform to elements.

fn map_err<F, B>(self, f: F) -> MapErr<Self, F> where
    F: Fn(Self::Error) -> B, 

Returns an iterator that applies a transform to errors.

fn nth(&mut self, n: usize) -> Result<Option<&Self::Item>, Self::Error>

Returns the nth element of the iterator.

fn position<F>(&mut self, f: F) -> Result<Option<usize>, Self::Error> where
    F: FnMut(&Self::Item) -> bool, 

Returns the position of the first element matching a predicate.

fn skip(self, n: usize) -> Skip<Self>

Returns an iterator which skips the first n elements.

fn skip_while<F>(self, f: F) -> SkipWhile<Self, F> where
    F: FnMut(&Self::Item) -> bool, 

Returns an iterator which skips the first sequence of elements matching a predicate.

fn take(self, n: usize) -> Take<Self>

Returns an iterator which only returns the first n elements.

fn take_while<F>(self, f: F) -> TakeWhile<Self, F> where
    F: FnMut(&Self::Item) -> bool, 

Returns an iterator which only returns the first sequence of elements matching a predicate.