Struct datafusion_physical_expr::expressions::DistinctCount

pub struct DistinctCount { /* private fields */ }

Expression for a COUNT(DISTINCT) aggregation.

Implementations

impl DistinctCount

pub fn new(
    input_data_types: Vec<DataType>,
    exprs: Vec<Arc<dyn PhysicalExpr>>,
    name: String,
    data_type: DataType
) -> Self

Create a new COUNT(DISTINCT) aggregate function.

Trait Implementations

impl AggregateExpr for DistinctCount

fn as_any(&self) -> &dyn Any

Return a reference to Any that can be used for downcasting

fn field(&self) -> Result<Field>

the field of the final result of this aggregation.

fn state_fields(&self) -> Result<Vec<Field>>

the fields that encapsulate the Accumulator’s state the number of fields here equals the number of states that the accumulator contains

fn expressions(&self) -> Vec<Arc<dyn PhysicalExpr>>

expressions that are passed to the Accumulator. Single-column aggregations such as sum return a single value, others (e.g. cov) return many.

fn create_accumulator(&self) -> Result<Box<dyn Accumulator>>

the accumulator used to accumulate values from the expressions. the accumulator expects the same number of arguments as expressions and must return states with the same description as state_fields

fn name(&self) -> &str

Human readable name such as "MIN(c2)". The default implementation returns placeholder text.

fn row_accumulator_supported(&self) -> bool

If the aggregate expression is supported by row format

fn supports_bounded_execution(&self) -> bool

Specifies whether this aggregate function can run using bounded memory. Any accumulator returning “true” needs to implement retract_batch.

fn create_row_accumulator(
    &self,
    _start_index: usize
) -> Result<Box<dyn RowAccumulator>>

RowAccumulator to access/update row-based aggregation state in-place. Currently, row accumulator only supports states of fixed-sized type.

fn reverse_expr(&self) -> Option<Arc<dyn AggregateExpr>>

Construct an expression that calculates the aggregate in reverse. Typically the “reverse” expression is itself (e.g. SUM, COUNT). For aggregates that do not support calculation in reverse, returns None (which is the default value).

fn create_sliding_accumulator(&self) -> Result<Box<dyn Accumulator>>

Creates accumulator implementation that supports retract

impl Debug for DistinctCount

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

Formats the value using the given formatter.