Struct MemoryBudget 

pub struct MemoryBudget {
    pub max_bytes: usize,
    /* private fields */
}

Memory budget for a single query execution.

Each blocking operator should call try_reserve before buffering data. When the budget is exhausted the operator returns an error, preventing OOM.

Fields

max_bytes: usize

Maximum bytes this query may use in blocking operators.

Implementations

impl MemoryBudget

pub const DEFAULT_MAX: usize

Default per-query budget (512 MB).

pub fn new(max_bytes: usize) -> Self

Create a new budget with max_bytes limit.

pub fn default_budget() -> Self

Create a budget with the default limit.

pub fn try_reserve(&self, bytes: usize) -> Result<bool, QueryError>

Try to reserve bytes additional memory.

Uses compare-and-swap so that the counter is only updated when the new total does not exceed the budget. On overflow or over-budget the counter is left unchanged (no observable side-effect).

Returns Ok(true) on success, Err when the budget would be exceeded or the request causes integer overflow.

pub fn release(&self, bytes: usize)

Release bytes from the budget (called when data is freed).

pub fn current(&self) -> usize

Current allocated bytes.

pub fn estimate_row_memory(row: &[Value]) -> usize

Rough estimate of the memory used by a single row (Vec heap + Value deep data).

pub fn estimate_rows_memory(rows: &[Vec<Value>]) -> usize

Rough estimate of the memory used by a slice of rows.

impl MemoryBudget

pub fn reserve(&self, bytes: usize) -> Result<MemoryReservation, QueryError>

Reserve bytes and return a MemoryReservation guard.

The guard releases the memory on drop. This is the recommended RAII alternative to the raw try_reserve / release pair.

Trait Implementations

impl Clone for MemoryBudget

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 MemoryBudget

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

Formats the value using the given formatter.