Struct datafusion_physical_expr::GroupsAccumulatorAdapter

pub struct GroupsAccumulatorAdapter { /* private fields */ }

An adapter that implements GroupsAccumulator for any Accumulator

While Accumulator are simpler to implement and can support more general calculations (like retractable window functions), they are not as fast as a specialized GroupsAccumulator. This interface bridges the gap so the group by operator only operates in terms of Accumulator.

Implementations

impl GroupsAccumulatorAdapter

pub fn new<F>(factory: F) -> Self

where F: Fn() -> Result<Box<dyn Accumulator>> + Send + 'static,

Create a new adapter that will create a new Accumulator for each group, using the specified factory function

Trait Implementations

impl GroupsAccumulator for GroupsAccumulatorAdapter

fn update_batch( &mut self, values: &[ArrayRef], group_indices: &[usize], opt_filter: Option<&BooleanArray>, total_num_groups: usize ) -> Result<()>

Updates the accumulator’s state from its arguments, encoded as a vector of ArrayRefs.

fn evaluate(&mut self, emit_to: EmitTo) -> Result<ArrayRef>

Returns the final aggregate value for each group as a single RecordBatch, resetting the internal state.

fn state(&mut self, emit_to: EmitTo) -> Result<Vec<ArrayRef>>

Returns the intermediate aggregate state for this accumulator, used for multi-phase grouping, resetting its internal state.

fn merge_batch( &mut self, values: &[ArrayRef], group_indices: &[usize], opt_filter: Option<&BooleanArray>, total_num_groups: usize ) -> Result<()>

Merges intermediate state (the output from Self::state) into this accumulator’s values.

fn size(&self) -> usize

Amount of memory used to store the state of this accumulator, in bytes. This function is called once per batch, so it should be O(n) to compute, not O(num_groups)