Struct datafusion_physical_expr::expressions::Stddev

pub struct Stddev { /* private fields */ }

STDDEV and STDDEV_SAMP (standard deviation) aggregate expression

Implementations

impl Stddev

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

Create a new STDDEV aggregate function

Trait Implementations

impl AggregateExpr for Stddev

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 row_accumulator_supported(&self) -> bool

If the aggregate expression is supported by row format

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 Stddev

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

Formats the value using the given formatter.