RelDistribution (Apache Calcite API)

All Superinterfaces:: Comparable<RelMultipleTrait>, RelMultipleTrait, RelTrait

public interface RelDistribution extends RelMultipleTrait

Description of the physical distribution of a relational expression.

TBD:

Can we shorten RelDistribution.Type.HASH_DISTRIBUTED to HASH, etc.
Do we need RelDistributions.DEFAULT?
RelDistributionTraitDef.convert(org.apache.calcite.plan.RelOptPlanner, org.apache.calcite.rel.RelNode, org.apache.calcite.rel.RelDistribution, boolean) does not create specific physical operators as it does in Drill. Drill will need to create rules; or we could allow "converters" to be registered with the planner that are not trait-defs.

Nested Class Summary

Nested Classes

Modifier and Type

Interface

Description

static enum

RelDistribution.Type

Type of distribution.
Method Summary

Modifier and Type

Method

Description

RelDistribution

apply(Mappings.TargetMapping mapping)

Applies mapping to this distribution trait.

List<Integer>

getKeys()

Returns the ordinals of the key columns.

RelDistribution.Type

getType()

Returns the type of distribution.

Methods inherited from interface java.lang.Comparable
compareTo

Methods inherited from interface org.apache.calcite.plan.RelMultipleTrait
isTop

Methods inherited from interface org.apache.calcite.plan.RelTrait
equals, getTraitDef, hashCode, isDefault, register, satisfies, toString

Method Details
- getType
  
  RelDistribution.Type getType()
  
  Returns the type of distribution.
- getKeys
  
  List<Integer> getKeys()
  
  Returns the ordinals of the key columns.
  Order is important for some types (RANGE); other types (HASH) consider it unimportant but impose an arbitrary order; other types (BROADCAST, SINGLETON) never have keys.
- apply
  
  RelDistribution apply(Mappings.TargetMapping mapping)
  
  Applies mapping to this distribution trait.
  Mapping can change the distribution trait only if it depends on distribution keys.
  For example if relation is HASH distributed by keys [0, 1], after applying a mapping (3, 2, 1, 0), the relation will have a distribution HASH(2,3) because distribution keys changed their ordinals.
  If mapping eliminates one of the distribution keys, the RelDistribution.Type.ANY distribution will be returned.
  If distribution doesn't have keys (BROADCAST or SINGLETON), method will return the same distribution.
  
  Specified by:
  
  apply in interface RelTrait
  
  Parameters:
  
  mapping - Mapping
  
  Returns:
  
  distribution with mapping applied