org.apache.calcite.plan.volcano

Class RelSubset

java.lang.Object

org.apache.calcite.rel.AbstractRelNode

org.apache.calcite.plan.volcano.RelSubset

All Implemented Interfaces:

Cloneable, RelOptNode, RelNode

public class RelSubset
extends AbstractRelNode

Subset of an equivalence class where all relational expressions have the same physical properties.

Physical properties are instances of the RelTraitSet, and consist of traits such as calling convention and collation (sort-order).

For some traits, a relational expression can have more than one instance. For example, R can be sorted on both [X] and [Y, Z]. In which case, R would belong to the sub-sets for [X] and [Y, Z]; and also the leading edges [Y] and [].

See Also:

RelNode, RelSet, RelTrait

Field Summary

Fields inherited from class org.apache.calcite.rel.AbstractRelNode

digest, id, rowType, traitSet

Method Summary

Methods

Modifier and Type	Method and Description
void	collectVariablesSet(Set<String> variableSet) Collects variables set by this expression.
void	collectVariablesUsed(Set<String> variableSet) Collects variables known to be used by this expression or its descendants.
protected String	computeDigest() Computes the digest.
RelOptCost	computeSelfCost(RelOptPlanner planner) Returns the cost of this plan (not including children).
RelNode	copy(RelTraitSet traitSet, List<RelNode> inputs) Creates a copy of this relational expression, perhaps changing traits and inputs.
protected RelDataType	deriveRowType()
void	explain(RelWriter pw) Describes the inputs and attributes of this relational expression.
RelNode	getBest()
Collection<RelNode>	getParentRels() Returns a list of relational expressions one of whose children is this subset.
List<RelNode>	getRelList() As getRels() but returns a list.
Iterable<RelNode>	getRels() Returns the rel nodes in this rel subset.
double	getRows() Returns an estimate of the number of rows this relational expression will return.
Set<String>	getVariablesSet()
Set<String>	getVariablesUsed()
boolean	isDistinct() Returns whether the same value will not come out twice.
boolean	isKey(ImmutableBitSet columns) Returns whether the result of this relational expression is uniquely identified by this columns with the given ordinals.
void	propagateBoostRemoval(VolcanoPlanner planner)

Methods inherited from class org.apache.calcite.rel.AbstractRelNode

accept, accept, childrenAccept, explainTerms, getChildExps, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getInputs, getQuery, getRelTypeName, getRowType, getTable, getTraitSet, getVariablesStopped, isValid, metadata, onRegister, recomputeDigest, register, replaceInput, sole, toString

Methods inherited from class java.lang.Object

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

Method Detail

getVariablesSet

public Set<String> getVariablesSet()

getVariablesUsed

public Set<String> getVariablesUsed()

getBest

public RelNode getBest()

copy

public RelNode copy(RelTraitSet traitSet,
           List<RelNode> inputs)

Description copied from interface: RelNode

Creates a copy of this relational expression, perhaps changing traits and inputs.

Sub-classes with other important attributes are encouraged to create variants of this method with more parameters.

Specified by:

copy in interface RelNode

Overrides:

copy in class AbstractRelNode

Parameters:

traitSet - Trait set

inputs - Inputs

Returns:

Copy of this relational expression, substituting traits and inputs

computeSelfCost

public RelOptCost computeSelfCost(RelOptPlanner planner)

Description copied from interface: RelNode

Returns the cost of this plan (not including children). The base implementation throws an error; derived classes should override.

NOTE jvs 29-Mar-2006: Don't call this method directly. Instead, use RelMetadataQuery.getNonCumulativeCost(org.apache.calcite.rel.RelNode), which gives plugins a chance to override the rel's default ideas about cost.

Specified by:

computeSelfCost in interface RelNode

Overrides:

computeSelfCost in class AbstractRelNode

Parameters:

planner - Planner for cost calculation

Returns:

Cost of this plan (not including children)

getRows

public double getRows()

Description copied from interface: RelNode

Returns an estimate of the number of rows this relational expression will return.

NOTE jvs 29-Mar-2006: Don't call this method directly. Instead, use RelMetadataQuery.getRowCount(org.apache.calcite.rel.RelNode), which gives plugins a chance to override the rel's default ideas about row count.

Specified by:

getRows in interface RelNode

Overrides:

getRows in class AbstractRelNode

Returns:

Estimate of the number of rows this relational expression will return

explain

public void explain(RelWriter pw)

Description copied from interface: RelNode

Describes the inputs and attributes of this relational expression. Each node should call super.explain, then call the RelWriterImpl.input(String, RelNode) and RelWriterImpl.item(String, Object) methods for each input and attribute.

Specified by:

explain in interface RelNode

Overrides:

explain in class AbstractRelNode

Parameters:

pw - Plan writer

computeDigest

protected String computeDigest()

Description copied from class: AbstractRelNode

Computes the digest. Does not modify this object.

Overrides:

computeDigest in class AbstractRelNode

Returns:

Digest

deriveRowType

protected RelDataType deriveRowType()

Overrides:

deriveRowType in class AbstractRelNode

isDistinct

public boolean isDistinct()

Description copied from interface: RelNode

Returns whether the same value will not come out twice. Default value is false, derived classes should override.

Specified by:

isDistinct in interface RelNode

Overrides:

isDistinct in class AbstractRelNode

Returns:

Whether the same value will not come out twice

isKey

public boolean isKey(ImmutableBitSet columns)

Description copied from interface: RelNode

Returns whether the result of this relational expression is uniquely identified by this columns with the given ordinals.

For example, if this relational expression is a LogicalTableScan to T(A, B, C, D) whose key is (A, B), then isKey([0, 1]) yields true, and isKey([0]) and isKey([0, 2]) yields false.

Specified by:

isKey in interface RelNode

Overrides:

isKey in class AbstractRelNode

Parameters:

columns - Ordinals of key columns

Returns:

Whether the given columns are a key or a superset of a key

getParentRels

public Collection<RelNode> getParentRels()

Returns a list of relational expressions one of whose children is this subset. The elements of the list are distinct.

propagateBoostRemoval

public void propagateBoostRemoval(VolcanoPlanner planner)

collectVariablesUsed

public void collectVariablesUsed(Set<String> variableSet)

Description copied from interface: RelNode

Collects variables known to be used by this expression or its descendants. By default, no such information is available and must be derived by analyzing sub-expressions, but some optimizer implementations may insert special expressions which remember such information.

Specified by:

collectVariablesUsed in interface RelNode

Overrides:

collectVariablesUsed in class AbstractRelNode

Parameters:

variableSet - receives variables used

collectVariablesSet

public void collectVariablesSet(Set<String> variableSet)

Description copied from interface: RelNode

Collects variables set by this expression. TODO: is this required?

Specified by:

collectVariablesSet in interface RelNode

Overrides:

collectVariablesSet in class AbstractRelNode

Parameters:

variableSet - receives variables known to be set by

getRels

public Iterable<RelNode> getRels()

Returns the rel nodes in this rel subset. All rels must have the same traits and are logically equivalent.

Returns:

all the rels in the subset

getRelList

public List<RelNode> getRelList()

As getRels() but returns a list.