Struct CountStatisticsRule 

pub struct CountStatisticsRule;

Optimizer rule that replaces count() with constants from table statistics

Implementations

impl CountStatisticsRule

pub fn new() -> Self

Examples found in repository

examples/common/mod.rs (line 53)

pub fn create_local_context() -> SessionContext {
    let state = SessionStateBuilder::new()
        .with_default_features()
        .with_optimizer_rule(Arc::new(CountStatisticsRule::new()))
        .with_optimizer_rule(Arc::new(MinMaxStatisticsRule::new()))
        .build();
    SessionContext::new_with_state(state)
}

/// Create a SessionContext configured for remote Zarr access (GCS, S3, etc).
///
/// Includes ZarrTableFactory for `CREATE EXTERNAL TABLE ... STORED AS ZARR`,
/// plus CountStatisticsRule and MinMaxStatisticsRule optimizers.
pub fn create_remote_context() -> SessionContext {
    let state = SessionStateBuilder::new()
        .with_default_features()
        .with_table_factories(HashMap::from([(
            "ZARR".to_string(),
            Arc::new(ZarrTableFactory) as _,
        )]))
        .with_optimizer_rule(Arc::new(CountStatisticsRule::new()))
        .with_optimizer_rule(Arc::new(MinMaxStatisticsRule::new()))
        .build();
    SessionContext::new_with_state(state)
}

Trait Implementations

impl Debug for CountStatisticsRule

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

Formats the value using the given formatter.

impl Default for CountStatisticsRule

fn default() -> CountStatisticsRule

Returns the “default value” for a type.

impl OptimizerRule for CountStatisticsRule

fn name(&self) -> &str

A human readable name for this optimizer rule

fn apply_order(&self) -> Option<ApplyOrder>

How should the rule be applied by the optimizer? See comments on ApplyOrder for details.

fn supports_rewrite(&self) -> bool

👎Deprecated since 47.0.0: This method is no longer used

Does this rule support rewriting owned plans (rather than by reference)?

fn rewrite( &self, plan: LogicalPlan, _config: &dyn OptimizerConfig, ) -> Result<Transformed<LogicalPlan>>

Try to rewrite plan to an optimized form, returning Transformed::yes if the plan was rewritten and Transformed::no if it was not.