Package org.apache.calcite.plan

Class RelTraitDef<T extends RelTrait>

java.lang.Object

org.apache.calcite.plan.RelTraitDef<T>

Type Parameters:

T - Trait that this trait definition is based upon

Direct Known Subclasses:

ConventionTraitDef, RelCollationTraitDef, RelDistributionTraitDef

public abstract class RelTraitDef<T extends RelTrait>
extends Object

RelTraitDef represents a class of RelTraits. Implementations of RelTraitDef may be singletons under the following conditions:

1. if the set of all possible associated RelTraits is finite and fixed (e.g. all RelTraits for this RelTraitDef are known at compile time). For example, the CallingConvention trait meets this requirement, because CallingConvention is effectively an enumeration.
2. Either
   • canConvert(RelOptPlanner, RelTrait, RelTrait) and convert(RelOptPlanner, RelNode, RelTrait, boolean) do not require planner-instance-specific information, or
   • the RelTraitDef manages separate sets of conversion data internally. See ConventionTraitDef for an example of this.

Otherwise, a new instance of RelTraitDef must be constructed and registered with each new planner instantiated.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	RelTraitDef()

Method Summary

Modifier and Type	Method	Description
abstract boolean	canConvert(RelOptPlanner planner, T fromTrait, T toTrait)	Tests whether the given RelTrait can be converted to another RelTrait.
final T	canonize(T trait)	Takes an arbitrary RelTrait and returns the canonical representation of that RelTrait.
abstract @Nullable RelNode	convert(RelOptPlanner planner, RelNode rel, T toTrait, boolean allowInfiniteCostConverters)	Converts the given RelNode to the given RelTrait.
void	deregisterConverterRule(RelOptPlanner planner, ConverterRule converterRule)	Provides notification that a particular ConverterRule has been de-registered from a RelOptPlanner.
abstract T	getDefault()	Returns the default member of this trait.
abstract String	getSimpleName()	Returns a simple name for this RelTraitDef (for use in RelNode.explain(org.apache.calcite.rel.RelWriter)).
abstract Class<T>	getTraitClass()	Returns the specific RelTrait type associated with this RelTraitDef.
boolean	multiple()	Whether a relational expression may possess more than one instance of this trait simultaneously.
void	registerConverterRule(RelOptPlanner planner, ConverterRule converterRule)	Provides notification of the registration of a particular ConverterRule with a RelOptPlanner.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

RelTraitDef

protected RelTraitDef()

Method Details

multiple

public boolean multiple()

Whether a relational expression may possess more than one instance of this trait simultaneously.

A subset has only one instance of a trait.

getTraitClass

public abstract Class<T> getTraitClass()

Returns the specific RelTrait type associated with this RelTraitDef.

getSimpleName

public abstract String getSimpleName()

Returns a simple name for this RelTraitDef (for use in RelNode.explain(org.apache.calcite.rel.RelWriter)).

canonize

public final T canonize(T trait)

Takes an arbitrary RelTrait and returns the canonical representation of that RelTrait. Canonized RelTrait objects may always be compared using the equality operator (==).

If an equal RelTrait has already been canonized and is still in use, it will be returned. Otherwise, the given RelTrait is made canonical and returned.

Parameters:

trait - a possibly non-canonical RelTrait

Returns:

a canonical RelTrait.

convert

public abstract @Nullable RelNode convert(RelOptPlanner planner,
 RelNode rel,
 T toTrait,
 boolean allowInfiniteCostConverters)

Converts the given RelNode to the given RelTrait.

Parameters:

planner - the planner requesting the conversion

rel - RelNode to convert

toTrait - RelTrait to convert to

allowInfiniteCostConverters - flag indicating whether infinite cost converters are allowed

Returns:

a converted RelNode or null if conversion is not possible

canConvert

public abstract boolean canConvert(RelOptPlanner planner,
 T fromTrait,
 T toTrait)

Tests whether the given RelTrait can be converted to another RelTrait.

Parameters:

planner - the planner requesting the conversion test

fromTrait - the RelTrait to convert from

toTrait - the RelTrait to convert to

Returns:

true if fromTrait can be converted to toTrait

registerConverterRule

public void registerConverterRule(RelOptPlanner planner,
 ConverterRule converterRule)

Provides notification of the registration of a particular ConverterRule with a RelOptPlanner. The default implementation does nothing.

Parameters:

planner - the planner registering the rule

converterRule - the registered converter rule

deregisterConverterRule

public void deregisterConverterRule(RelOptPlanner planner,
 ConverterRule converterRule)

Provides notification that a particular ConverterRule has been de-registered from a RelOptPlanner. The default implementation does nothing.

Parameters:

planner - the planner registering the rule

converterRule - the registered converter rule

getDefault

public abstract T getDefault()

Returns the default member of this trait.