Struct datafusion_physical_optimizer::output_requirements::OutputRequirements

pub struct OutputRequirements { /* private fields */ }

This rule either adds or removes OutputRequirementss to/from the physical plan according to its mode attribute, which is set by the constructors new_add_mode and new_remove_mode. With this rule, we can keep track of the global requirements (ordering and distribution) across rules.

The primary usecase of this node and rule is to specify and preserve the desired output ordering and distribution the entire plan. When sending to a single client, a single partition may be desirable, but when sending to a multi-partitioned writer, keeping multiple partitions may be better.

Implementations

impl OutputRequirements

pub fn new_add_mode() -> Self

Create a new rule which works in Add mode; i.e. it simply adds a top-level OutputRequirementExec into the physical plan to keep track of global ordering and distribution requirements if there are any. Note that this rule should run at the beginning.

pub fn new_remove_mode() -> Self

Create a new rule which works in Remove mode; i.e. it simply removes the top-level OutputRequirementExec from the physical plan if there is any. We do this because a OutputRequirementExec is an ancillary, non-executable operator whose sole purpose is to track global requirements during optimization. Therefore, a OutputRequirementExec should not appear in the final plan.

Trait Implementations

impl Debug for OutputRequirements

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

Formats the value using the given formatter.

impl PhysicalOptimizerRule for OutputRequirements

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 valid 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.