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Accumulator

alopex_sql::executor::query::aggregate

Trait Accumulator 

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pub trait Accumulator: Send {
    // Required methods
    fn update(&mut self, value: Option<SqlValue>) -> Result<()>;
    fn state(&self) -> Result<Vec<SqlValue>>;
    fn merge(&mut self, state: &[SqlValue]) -> Result<()>;
    fn finalize(&self) -> Result<SqlValue>;
    fn clone_box(&self) -> Box<dyn Accumulator>;

    // Provided method
    fn retained_bytes(&self) -> u64 { ... }
}
Expand description

Accumulator interface for aggregate function execution.

Required Methods§

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fn update(&mut self, value: Option<SqlValue>) -> Result<()>

Update the accumulator with a new value (None for COUNT(*) rows).

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fn state(&self) -> Result<Vec<SqlValue>>

Return the serializable partial aggregate state.

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fn merge(&mut self, state: &[SqlValue]) -> Result<()>

Merge a partial state produced by an accumulator of the same function.

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fn finalize(&self) -> Result<SqlValue>

Finalize the accumulator and return the resulting SqlValue.

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fn clone_box(&self) -> Box<dyn Accumulator>

Clone the accumulator as a trait object.

Provided Methods§

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fn retained_bytes(&self) -> u64

Estimated bytes retained by dynamically allocated accumulator state.

Window execution uses this to charge the shared operator memory budget while an accumulator is alive.

Trait Implementations§

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impl Clone for Box<dyn Accumulator>

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fn clone(&self) -> Self

Returns a duplicate of the value. Read more
1.0.0 (const: unstable) · Source§

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

Performs copy-assignment from source. Read more

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§