Struct DistinctCountAccumulator 

struct DistinctCountAccumulator {
    values: HashSet<ScalarValue, RandomState>,
    state_data_type: DataType,
}

General purpose distinct accumulator that works for any DataType by using ScalarValue.

It stores intermediate results as a ListArray

Note that many types have specialized accumulators that are (much) more efficient such as PrimitiveDistinctCountAccumulator and BytesDistinctCountAccumulator

Fields

values: HashSet<ScalarValue, RandomState>

state_data_type: DataType

Implementations

impl DistinctCountAccumulator

fn fixed_size(&self) -> usize

fn full_size(&self) -> usize

Trait Implementations

impl Accumulator for DistinctCountAccumulator

fn state(&mut self) -> Result<Vec<ScalarValue>>

Returns the distinct values seen so far as (one element) ListArray.

fn merge_batch(&mut self, states: &[ArrayRef]) -> Result<()>

Merges multiple sets of distinct values into the current set.

The input to this function is a ListArray with multiple rows, where each row contains the values from a partial aggregate’s phase (e.g. the result of calling Self::state on multiple accumulators).

fn update_batch(&mut self, values: &[ArrayRef]) -> Result<()>

Updates the accumulator’s state from its input.

fn evaluate(&mut self) -> Result<ScalarValue>

Returns the final aggregate value, consuming the internal state.

fn size(&self) -> usize

Returns the allocated size required for this accumulator, in bytes, including Self.

fn retract_batch( &mut self, _values: &[Arc<dyn Array>], ) -> Result<(), DataFusionError>

Retracts (removed) an update (caused by the given inputs) to accumulator’s state.

fn supports_retract_batch(&self) -> bool

Does the accumulator support incrementally updating its value by removing values.

impl Debug for DistinctCountAccumulator

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

Formats the value using the given formatter.