Struct TranslateApplyRule

pub struct TranslateApplyRule {
    enable_share_plan: bool,
}

General Unnesting based on the paper Unnesting Arbitrary Queries: Translate the apply into a canonical form.

Before:

    LogicalApply
   /            \
 LHS           RHS

After:

     LogicalJoin
   /            \
 LHS        LogicalApply
            /           \
         Domain         RHS

Fields

enable_share_plan: bool

Implementations

impl TranslateApplyRule

pub fn create(enable_share_plan: bool) -> Box<dyn FallibleRule>

fn rewrite( plan: &PlanRef, correlated_indices: Vec<usize>, offset: usize, index_mapping: &mut ColIndexMapping, data_types: &mut HashMap<usize, DataType>, index: &mut usize, ) -> Option<PlanRef>

Rewrite LogicalApply’s left according to correlated_indices.

Assumption: only LogicalJoin, LogicalScan, LogicalProject and LogicalFilter are in the left.

fn rewrite_join( join: &LogicalJoin, required_col_idx: Vec<usize>, offset: usize, index_mapping: &mut ColIndexMapping, data_types: &mut HashMap<usize, DataType>, index: &mut usize, ) -> Option<PlanRef>

fn rewrite_apply( apply: &LogicalApply, required_col_idx: Vec<usize>, offset: usize, index_mapping: &mut ColIndexMapping, data_types: &mut HashMap<usize, DataType>, index: &mut usize, ) -> Option<PlanRef>

            LogicalApply
           /            \
    LogicalApply       RHS1
   /            \
 LHS           RHS2

A common structure of multi scalar subqueries is a chain of LogicalApply. To avoid exponential growth of the domain operator, we need to rewrite the apply and try to simplify the domain as much as possible. We use a top-down apply order to rewrite the apply, so that we don’t need to handle operator like project and aggregation generated by the domain calculation. As a cost, we need to add a flag translated to the apply operator to remind translate_apply_rule that the apply has been translated.

fn rewrite_scan( scan: &LogicalScan, required_col_idx: Vec<usize>, offset: usize, index_mapping: &mut ColIndexMapping, data_types: &mut HashMap<usize, DataType>, index: &mut usize, ) -> Option<PlanRef>

Trait Implementations

impl Description for TranslateApplyRule

fn description(&self) -> &str

impl InfallibleRule for TranslateApplyRule

fn apply(&self, plan: PlanRef) -> Option<PlanRef>

Apply the rule to the plan node.