Struct LimitedDistinctAggregation 

pub struct LimitedDistinctAggregation {}

An optimizer rule that passes a limit hint into grouped aggregations which don’t require all rows in the group to be processed for correctness. Example queries fitting this description are:

• SELECT distinct l_orderkey FROM lineitem LIMIT 10;
• SELECT l_orderkey FROM lineitem GROUP BY l_orderkey LIMIT 10;

Implementations

impl LimitedDistinctAggregation

pub fn new() -> Self

Create a new LimitedDistinctAggregation

fn transform_agg( aggr: &AggregateExec, limit: usize, ) -> Option<Arc<dyn ExecutionPlan>>

fn transform_limit( plan: Arc<dyn ExecutionPlan>, ) -> Option<Arc<dyn ExecutionPlan>>

transform_limit matches an AggregateExec as the child of a LocalLimitExec or GlobalLimitExec and pushes the limit into the aggregation as a soft limit when there is a group by, but no sorting, no aggregate expressions, and no filters in the aggregation

Trait Implementations

impl Debug for LimitedDistinctAggregation

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

Formats the value using the given formatter.

impl Default for LimitedDistinctAggregation

fn default() -> Self

Returns the “default value” for a type.

impl PhysicalOptimizerRule for LimitedDistinctAggregation

fn optimize( &self, plan: Arc<dyn ExecutionPlan>, config: &ConfigOptions, ) -> Result<Arc<dyn ExecutionPlan>>

Rewrite plan to an optimized form

fn name(&self) -> &str

A human readable name for this optimizer rule

fn schema_check(&self) -> bool

A flag to indicate whether the physical planner should validate that the rule will not change the schema of the plan after the rewriting. Some of the optimization rules might change the nullable properties of the schema and should disable the schema check.