Struct FileWriter

pub struct FileWriter<W: Write> { /* private fields */ }

Available on crate feature io_ipc only.

Arrow file writer

Implementations

impl<R: Read + Seek + Write> FileWriter<R>

pub fn try_from_file( writer: R, metadata: FileMetadata, options: WriteOptions, ) -> PolarsResult<FileWriter<R>>

Creates a new FileWriter from an existing file, seeking to the last message and appending new messages afterwards. Users call finish to write the footer (with both) the existing and appended messages on it.

Error

This function errors iff:

• the file’s endianness is not the native endianness (not yet supported)
• the file is not a valid Arrow IPC file

impl<W: Write> FileWriter<W>

pub fn try_new( writer: W, schema: ArrowSchemaRef, ipc_fields: Option<Vec<IpcField>>, options: WriteOptions, ) -> PolarsResult<Self>

Creates a new FileWriter and writes the header to writer

pub fn new( writer: W, schema: ArrowSchemaRef, ipc_fields: Option<Vec<IpcField>>, options: WriteOptions, ) -> Self

Creates a new FileWriter.

pub fn into_inner(self) -> W

Consumes itself into the inner writer

pub fn get_scratches(&mut self) -> EncodedData

Get the inner memory scratches so they can be reused in a new writer. This can be utilized to save memory allocations for performance reasons.

pub fn set_scratches(&mut self, scratches: EncodedData)

Set the inner memory scratches so they can be reused in a new writer. This can be utilized to save memory allocations for performance reasons.

pub fn start(&mut self) -> PolarsResult<()>

Writes the header and first (schema) message to the file.

Errors

Errors if the file has been started or has finished.

pub fn write( &mut self, chunk: &RecordBatchT<Box<dyn Array>>, ipc_fields: Option<&[IpcField]>, ) -> PolarsResult<()>

Writes RecordBatchT to the file

pub fn write_encoded( &mut self, encoded_dictionaries: &[EncodedData], encoded_message: &EncodedData, ) -> PolarsResult<()>

pub fn write_encoded_record_batch( &mut self, encoded_message: &EncodedData, ) -> PolarsResult<()>

pub fn finish(&mut self) -> PolarsResult<()>

Write footer and closing tag, then mark the writer as done

pub fn set_custom_schema_metadata(&mut self, custom_metadata: Arc<Metadata>)

Sets custom schema metadata. Must be called before start is called