Struct datafusion_physical_expr::expressions::LastValue

pub struct LastValue {
    pub data_type: DataType,
    /* private fields */
}

LAST_VALUE aggregate expression

Fields

data_type: DataType

Implementations

impl LastValue

pub fn new( expr: Arc<dyn PhysicalExpr>, name: impl Into<String>, data_type: DataType ) -> Self

Creates a new LAST_VALUE aggregation function.

Trait Implementations

impl AggregateExpr for LastValue

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 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 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 name(&self) -> &str

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

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

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.

impl Debug for LastValue

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

Formats the value using the given formatter.

impl PartialEq<dyn Any + 'static> for LastValue

fn eq(&self, other: &dyn Any) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.