Enum AggregateMode 

pub enum AggregateMode {
    Partial,
    Final,
    FinalPartitioned,
    Single,
    SinglePartitioned,
    PartialReduce,
}

Aggregation modes

See Accumulator::state for background information on multi-phase aggregation and how these modes are used.

Variants and their input/output modes

Each variant can be characterized by its AggregateInputMode and AggregateOutputMode:

                      | Input: Raw data           | Input: Partial state
Output: Final values  | Single, SinglePartitioned | Final, FinalPartitioned
Output: Partial state | Partial                   | PartialReduce

Use AggregateMode::input_mode and AggregateMode::output_mode to query these properties.

Variants

Partial

One of multiple layers of aggregation, any input partitioning

Partial aggregate that can be applied in parallel across input partitions.

This is the first phase of a multi-phase aggregation.

Final

Final of multiple layers of aggregation, in exactly one partition

Final aggregate that produces a single partition of output by combining the output of multiple partial aggregates.

This is the second phase of a multi-phase aggregation.

This mode requires that the input is a single partition

Note: Adjacent Partial and Final mode aggregation is equivalent to a Single mode aggregation node. The Final mode is required since this is used in an intermediate step. The CombinePartialFinalAggregate physical optimizer rule will replace this combination with Single mode for more efficient execution.

FinalPartitioned

Final of multiple layers of aggregation, input is Partitioned

Final aggregate that works on pre-partitioned data.

This mode requires that all rows with a particular grouping key are in the same partitions, such as is the case with Hash repartitioning on the group keys. If a group key is duplicated, duplicate groups would be produced

Single

Single layer of Aggregation, input is exactly one partition

Applies the entire logical aggregation operation in a single operator, as opposed to Partial / Final modes which apply the logical aggregation using two operators.

This mode requires that the input is a single partition (like Final)

SinglePartitioned

Single layer of Aggregation, input is Partitioned

Applies the entire logical aggregation operation in a single operator, as opposed to Partial / Final modes which apply the logical aggregation using two operators.

This mode requires that the input has more than one partition, and is partitioned by group key (like FinalPartitioned).

PartialReduce

Combine multiple partial aggregations to produce a new partial aggregation.

Input is intermediate accumulator state (like Final), but output is also intermediate accumulator state (like Partial). This enables tree-reduce aggregation strategies where partial results from multiple workers are combined in multiple stages before a final evaluation.

              Final
           /        \
    PartialReduce   PartialReduce
    /         \      /         \
 Partial   Partial  Partial   Partial

Implementations

impl AggregateMode

pub fn input_mode(&self) -> AggregateInputMode

Returns the AggregateInputMode for this mode: whether this stage consumes raw input data or intermediate accumulator state.

See the table above for details.

pub fn output_mode(&self) -> AggregateOutputMode

Returns the AggregateOutputMode for this mode: whether this stage produces intermediate accumulator state or final output values.

See the table above for details.

Trait Implementations

impl Clone for AggregateMode

fn clone(&self) -> AggregateMode

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for AggregateMode

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

Formats the value using the given formatter.

impl PartialEq for AggregateMode

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl Copy for AggregateMode

impl Eq for AggregateMode

impl StructuralPartialEq for AggregateMode