Enum ChunkSize 

pub enum ChunkSize {
    Fixed(usize),
    Adaptive,
    Custom(fn(u64) -> usize),
}

How much data a streaming engine reads per chunk.

The unit is bytes, everywhere. Chunk size targets how much of the source is read at once, so it is expressed in bytes rather than rows, whose width varies per dataset. Every engine and binding agrees: ChunkSize::Fixed(65_536) and Python’s chunk_size=65536 both mean a 64 KiB target, whether the source is a file, a byte stream, or a URL. A parser may exceed that target to keep one logical record intact.

Chunk size never changes what a profile contains — only the granularity at which the source is read, progress is emitted, and chunk-level stop conditions are evaluated.

Variants

Fixed(usize)

Fixed chunk-size target in bytes.

Adaptive

Let the engine choose the chunk size (default).

Each engine resolves this against what it knows: the incremental engine derives a size from its memory limit and the file size, while the async reader — whose source has no length to adapt to — uses a fixed working-set target. Unlike Fixed, the resulting size is not a guarantee, so it is not something to assert against.

Custom(fn(u64) -> usize)

Custom sizing function, given the source size in bytes and returning a chunk size in bytes. Cannot derive Debug/Clone with a function pointer.

Implementations

impl ChunkSize

pub fn calculate(&self, file_size_bytes: u64) -> usize

Resolve to a concrete chunk size in bytes for a source of the given size.

This is a standalone helper, not the path any engine takes: Fixed and Custom resolve exactly as an engine would, but Adaptive here is derived from system available memory, whereas an engine derives it from its own configured memory limit. Do not use this to predict what an engine will do with Adaptive.

Trait Implementations

impl Clone for ChunkSize

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ChunkSize

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ChunkSize

fn default() -> Self

Returns the “default value” for a type.