org.apache.calcite.rel

Interface RelDistribution

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 and Description
static class	RelDistribution.Type Type of distribution.

Method Summary

Modifier and Type	Method and 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 org.apache.calcite.plan.RelMultipleTrait

isTop

Methods inherited from interface org.apache.calcite.plan.RelTrait

equals, getTraitDef, hashCode, isDefault, register, satisfies, toString

Methods inherited from interface java.lang.Comparable

compareTo

Method Detail

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