org.apache.calcite.rel

Class RelCollationTraitDef

java.lang.Object

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

org.apache.calcite.rel.RelCollationTraitDef

public class RelCollationTraitDef
extends RelTraitDef<RelCollation>

Definition of the ordering trait.

Ordering is a physical property (i.e. a trait) because it can be changed without loss of information. The converter to do this is the Sort operator.

Unlike other current traits, a RelNode can have more than one value of this trait simultaneously. For example, LogicalTableScan(table=TIME_BY_DAY) might be sorted by {the_year, the_month, the_date} and also by {time_id}. We have to allow a RelNode to belong to more than one RelSubset (these RelSubsets are always in the same set).

Field Summary

Fields

Modifier and Type	Field and Description
static RelCollationTraitDef	INSTANCE

Method Summary

Modifier and Type	Method and Description
boolean	canConvert(RelOptPlanner planner, RelCollation fromTrait, RelCollation toTrait) Tests whether the given RelTrait can be converted to another RelTrait.
@Nullable RelNode	convert(RelOptPlanner planner, RelNode rel, RelCollation toCollation, boolean allowInfiniteCostConverters) Converts the given RelNode to the given RelTrait.
RelCollation	getDefault() Returns the default member of this trait.
String	getSimpleName() Returns a simple name for this RelTraitDef (for use in RelNode.explain(org.apache.calcite.rel.RelWriter)).
Class<RelCollation>	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.

Methods inherited from class org.apache.calcite.plan.RelTraitDef

canonize, deregisterConverterRule, registerConverterRule

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final RelCollationTraitDef INSTANCE

Method Detail

getTraitClass

public Class<RelCollation> getTraitClass()

Description copied from class: RelTraitDef

Returns the specific RelTrait type associated with this RelTraitDef.

Specified by:

getTraitClass in class RelTraitDef<RelCollation>

getSimpleName

public String getSimpleName()

Description copied from class: RelTraitDef

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

Specified by:

getSimpleName in class RelTraitDef<RelCollation>

multiple

public boolean multiple()

Description copied from class: RelTraitDef

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

A subset has only one instance of a trait.

Overrides:

multiple in class RelTraitDef<RelCollation>

getDefault

public RelCollation getDefault()

Description copied from class: RelTraitDef

Returns the default member of this trait.

Specified by:

getDefault in class RelTraitDef<RelCollation>

convert

public @Nullable RelNode convert(RelOptPlanner planner,
                                 RelNode rel,
                                 RelCollation toCollation,
                                 boolean allowInfiniteCostConverters)

Description copied from class: RelTraitDef

Converts the given RelNode to the given RelTrait.

Specified by:

convert in class RelTraitDef<RelCollation>

Parameters:

planner - the planner requesting the conversion

rel - RelNode to convert

toCollation - 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 boolean canConvert(RelOptPlanner planner,
                          RelCollation fromTrait,
                          RelCollation toTrait)

Description copied from class: RelTraitDef

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

Specified by:

canConvert in class RelTraitDef<RelCollation>

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