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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	RelSubset.CheapestPlanReplacer Visitor which walks over a tree of RelSets, replacing each node with the cheapest implementation of the expression.

Nested classes/interfaces inherited from interface org.apache.calcite.rel.RelNode

RelNode.Context

Field Summary

Fields

Modifier and Type	Field and Description
(package private) RelNode	best best known plan
(package private) RelOptCost	bestCost cost of best known plan (it may have improved since)
(package private) boolean	boosted Flag indicating whether this RelSubset's importance was artificially boosted.
private static org.slf4j.Logger	LOGGER
(package private) RelSet	set The set this subset belongs to.
(package private) long	timestamp Timestamp for metadata validity

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

digest, id, rowType, traitSet

Constructor Summary

Constructors

Constructor and Description
RelSubset(RelOptCluster cluster, RelSet set, RelTraitSet traits)

Method Summary

Modifier and Type	Method and Description
(package private) void	add(RelNode rel) Adds expression rel to this subset.
(package private) RelNode	buildCheapestPlan(VolcanoPlanner planner) Recursively builds a tree consisting of the cheapest plan at each node.
void	collectVariablesSet(Set<CorrelationId> variableSet) Collects variables set by this expression.
void	collectVariablesUsed(Set<CorrelationId> variableSet) Collects variables known to be used by this expression or its descendants.
private void	computeBestCost(RelOptPlanner planner) Computes the best RelNode in this subset.
protected String	computeDigest() Computes the digest.
RelOptCost	computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) 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()
double	estimateRowCount(RelMetadataQuery mq) Returns an estimate of the number of rows this relational expression will return.
void	explain(RelWriter pw) Describes the inputs and attributes of this relational expression.
RelNode	getBest()
RelNode	getOriginal()
Collection<RelNode>	getParentRels() Returns a list of relational expressions one of whose children is this subset.
(package private) Set<RelNode>	getParents() Returns the collection of RelNodes one of whose inputs is in this subset.
(package private) Set<RelSubset>	getParentSubsets(VolcanoPlanner planner) Returns the collection of distinct subsets that contain a RelNode one of whose inputs is in this subset.
List<RelNode>	getRelList() As getRels() but returns a list.
Iterable<RelNode>	getRels() Returns the rel nodes in this rel subset.
(package private) RelSet	getSet()
private static List<RelSubset>	inputSubsets(RelNode parent)
void	propagateBoostRemoval(VolcanoPlanner planner)
(package private) void	propagateCostImprovements(VolcanoPlanner planner, RelMetadataQuery mq, RelNode rel, Set<RelSubset> activeSet) Checks whether a relexp has made its subset cheaper, and if it so, recursively checks whether that subset's parents have gotten cheaper.
(package private) void	propagateCostImprovements0(VolcanoPlanner planner, RelMetadataQuery mq, RelNode rel, Set<RelSubset> activeSet)

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

accept, accept, childrenAccept, computeSelfCost, explainTerms, getChildExps, getCluster, getCollationList, getConvention, getCorrelVariable, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getInputs, getQuery, getRelTypeName, getRows, getRowType, getTable, getTraitSet, getVariablesSet, getVariablesStopped, isDistinct, isKey, isValid, 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

Field Detail

LOGGER

private static final org.slf4j.Logger LOGGER

bestCost

RelOptCost bestCost

cost of best known plan (it may have improved since)

set

final RelSet set

The set this subset belongs to.

best

RelNode best

best known plan

timestamp

long timestamp

Timestamp for metadata validity

boosted

boolean boosted

Flag indicating whether this RelSubset's importance was artificially boosted.

Constructor Detail

RelSubset

RelSubset(RelOptCluster cluster,
          RelSet set,
          RelTraitSet traits)

Method Detail

computeBestCost

private void computeBestCost(RelOptPlanner planner)

Computes the best RelNode in this subset.

Only necessary when a subset is created in a set that has subsets that subsume it. Rationale:

1. If the are no subsuming subsets, the subset is initially empty.
2. After creation, best and bestCost are maintained incrementally by propagateCostImprovements0(org.apache.calcite.plan.volcano.VolcanoPlanner, org.apache.calcite.rel.metadata.RelMetadataQuery, org.apache.calcite.rel.RelNode, java.util.Set<org.apache.calcite.plan.volcano.RelSubset>) and RelSet.mergeWith(VolcanoPlanner, RelSet).

getBest

public RelNode getBest()

getOriginal

public RelNode getOriginal()

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,
                                  RelMetadataQuery mq)

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

mq - Metadata query

Returns:

Cost of this plan (not including children)

estimateRowCount

public double estimateRowCount(RelMetadataQuery mq)

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:

estimateRowCount in interface RelNode

Overrides:

estimateRowCount in class AbstractRelNode

Parameters:

mq - Metadata query

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

getParents

Set<RelNode> getParents()

Returns the collection of RelNodes one of whose inputs is in this subset.

getParentSubsets

Set<RelSubset> getParentSubsets(VolcanoPlanner planner)

Returns the collection of distinct subsets that contain a RelNode one of whose inputs is in this subset.

inputSubsets

private static List<RelSubset> inputSubsets(RelNode parent)

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.

getSet

RelSet getSet()

add

void add(RelNode rel)

Adds expression rel to this subset.

buildCheapestPlan

RelNode buildCheapestPlan(VolcanoPlanner planner)

Recursively builds a tree consisting of the cheapest plan at each node.

propagateCostImprovements

void propagateCostImprovements(VolcanoPlanner planner,
                               RelMetadataQuery mq,
                               RelNode rel,
                               Set<RelSubset> activeSet)

Checks whether a relexp has made its subset cheaper, and if it so, recursively checks whether that subset's parents have gotten cheaper.

Parameters:

planner - Planner

mq - Metadata query

rel - Relational expression whose cost has improved

activeSet - Set of active subsets, for cycle detection

propagateCostImprovements0

void propagateCostImprovements0(VolcanoPlanner planner,
                                RelMetadataQuery mq,
                                RelNode rel,
                                Set<RelSubset> activeSet)

propagateBoostRemoval

public void propagateBoostRemoval(VolcanoPlanner planner)

collectVariablesUsed

public void collectVariablesUsed(Set<CorrelationId> 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<CorrelationId> 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.