Struct CowBatch 

pub struct CowBatch<T> {
    pub items: Vec<Arc<T>>,
}

Batch of Arc-shared items with copy-on-write mutation via Arc::make_mut.

Prefer owned Vec + InPlaceTransform::transform_rows_inplace / InPlaceTransform::transform_changes_inplace when sharing is not required. Use CowBatch only when the same items may be shared across holders and mutation must not affect other owners.

Cost of apply_inplace

Self::apply_inplace always calls Arc::make_mut before invoking the transform. When an item’s strong count is greater than one, make_mut clones even if the transform is a no-op (e.g. crate::pipeline::Passthrough). Unique arcs (refcount 1) are mutated without allocation regardless of whether the transform writes.

Fields

items: Vec<Arc<T>>

Shared items; mutated through Arc::make_mut in Self::apply_inplace.

Implementations

impl<T> CowBatch<T>

pub fn new(items: Vec<Arc<T>>) -> Self

Create a batch from already-shared items.

pub fn from_owned(items: Vec<T>) -> Self

Create a batch by wrapping each owned item in a fresh Arc (refcount 1).

pub fn len(&self) -> usize

Number of items in the batch.

pub fn is_empty(&self) -> bool

Whether the batch is empty.

pub fn into_items(self) -> Vec<Arc<T>>

Consume the batch, returning the underlying Arcs.

impl CowBatch<Row>

pub fn apply_inplace(&mut self, t: &impl InPlaceTransform) -> Result<()>

Apply an in-place transform with Arc COW semantics.

Always calls Arc::make_mut per item. Clones when the arc is shared (strong count > 1), including when t is a no-op such as crate::pipeline::Passthrough. Unique arcs are mutated without allocation.

impl CowBatch<Change>

pub fn apply_inplace(&mut self, t: &impl InPlaceTransform) -> Result<()>

Apply an in-place transform with Arc COW semantics.

Always calls Arc::make_mut per item. Clones when the arc is shared (strong count > 1), including when t is a no-op such as crate::pipeline::Passthrough. Unique arcs are mutated without allocation.

impl CowBatch<Relation>

pub fn apply_inplace(&mut self, t: &impl InPlaceTransform) -> Result<()>

Apply an in-place transform with Arc COW semantics for relations.

Trait Implementations

impl<T: Clone> Clone for CowBatch<T>

fn clone(&self) -> CowBatch<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug> Debug for CowBatch<T>

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

Formats the value using the given formatter.