Package org.apache.calcite.rel.core

Class Correlate

java.lang.Object

org.apache.calcite.rel.AbstractRelNode

org.apache.calcite.rel.BiRel

org.apache.calcite.rel.core.Correlate

All Implemented Interfaces:

java.lang.Cloneable, RelOptNode, RelNode

Direct Known Subclasses:

EnumerableCorrelate, LogicalCorrelate

public abstract class Correlate
extends BiRel

A relational operator that performs nested-loop joins.

It behaves like a kind of Join, but works by setting variables in its environment and restarting its right-hand input.

Correlate is not a join since: typical rules should not match Correlate.

A Correlate is used to represent a correlated query. One implementation strategy is to de-correlate the expression.

Mapping of physical operations to logical ones

Physical operation	Logical operation
NestedLoops	Correlate(A, B, regular)
NestedLoopsOuter	Correlate(A, B, outer)
NestedLoopsSemi	Correlate(A, B, semi)
NestedLoopsAnti	Correlate(A, B, anti)
HashJoin	EquiJoin(A, B)
HashJoinOuter	EquiJoin(A, B, outer)
HashJoinSemi	SemiJoin(A, B, semi)
HashJoinAnti	SemiJoin(A, B, anti)

See Also:

CorrelationId

Nested Class Summary

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

RelNode.Context

Field Summary

Fields

Modifier and Type	Field	Description
protected CorrelationId	correlationId
protected SemiJoinType	joinType
protected ImmutableBitSet	requiredColumns

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

left, right

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

digest, id, rowType, traitSet

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Correlate(RelOptCluster cluster, RelTraitSet traits, RelNode left, RelNode right, CorrelationId correlationId, ImmutableBitSet requiredColumns, SemiJoinType joinType)	Creates a Correlate.
	Correlate(RelInput input)	Creates a Correlate by parsing serialized output.

Method Summary

Modifier and Type	Method	Description
RelOptCost	computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq)	Returns the cost of this plan (not including children).
Correlate	copy(RelTraitSet traitSet, java.util.List<RelNode> inputs)	Creates a copy of this relational expression, perhaps changing traits and inputs.
abstract Correlate	copy(RelTraitSet traitSet, RelNode left, RelNode right, CorrelationId correlationId, ImmutableBitSet requiredColumns, SemiJoinType joinType)
protected RelDataType	deriveRowType()
RelWriter	explainTerms(RelWriter pw)	Describes the inputs and attributes of this relational expression.
CorrelationId	getCorrelationId()	Returns the correlating expressions.
java.lang.String	getCorrelVariable()	Returns the name of the variable which is to be implicitly set at runtime each time a row is returned from the first input of this relational expression; or null if there is no variable.
SemiJoinType	getJoinType()
ImmutableBitSet	getRequiredColumns()	Returns the required columns in left relation required for the correlation in the right.
java.util.Set<CorrelationId>	getVariablesSet()	Returns the variables that are set in this relational expression but also used and therefore not available to parents of this relational expression.
boolean	isValid(Litmus litmus, RelNode.Context context)	Returns whether this relational expression is valid.

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

childrenAccept, getInputs, getLeft, getRight, replaceInput

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

accept, accept, collectVariablesSet, collectVariablesUsed, computeDigest, computeSelfCost, estimateRowCount, explain, getChildExps, getCluster, getCollationList, getConvention, getDescription, getDigest, getExpectedInputRowType, getId, getInput, getQuery, getRelTypeName, getRows, getRowType, getTable, getTraitSet, getVariablesStopped, isDistinct, isKey, isValid, metadata, onRegister, recomputeDigest, register, sole, toString

Methods inherited from class java.lang.Object

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

Field Detail

correlationId

protected final CorrelationId correlationId

requiredColumns

protected final ImmutableBitSet requiredColumns

joinType

protected final SemiJoinType joinType

Constructor Detail

Correlate

protected Correlate(RelOptCluster cluster,
                    RelTraitSet traits,
                    RelNode left,
                    RelNode right,
                    CorrelationId correlationId,
                    ImmutableBitSet requiredColumns,
                    SemiJoinType joinType)

Creates a Correlate.

Parameters:

cluster - Cluster this relational expression belongs to

left - Left input relational expression

right - Right input relational expression

correlationId - Variable name for the row of left input

requiredColumns - Set of columns that are used by correlation

joinType - Join type

Correlate

public Correlate(RelInput input)

Creates a Correlate by parsing serialized output.

Parameters:

input - Input representation

Method Detail

isValid

public boolean isValid(Litmus litmus,
                       RelNode.Context context)

Description copied from interface: RelNode

Returns whether this relational expression is valid.

If assertions are enabled, this method is typically called with litmus = THROW, as follows:

assert rel.isValid(Litmus.THROW)

This signals that the method can throw an AssertionError if it is not valid.

Specified by:

isValid in interface RelNode

Overrides:

isValid in class AbstractRelNode

Parameters:

litmus - What to do if invalid

context - Context for validity checking

Returns:

Whether relational expression is valid

copy

public Correlate copy(RelTraitSet traitSet,
                      java.util.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

copy

public abstract Correlate copy(RelTraitSet traitSet,
                               RelNode left,
                               RelNode right,
                               CorrelationId correlationId,
                               ImmutableBitSet requiredColumns,
                               SemiJoinType joinType)

getJoinType

public SemiJoinType getJoinType()

deriveRowType

protected RelDataType deriveRowType()

Overrides:

deriveRowType in class AbstractRelNode

explainTerms

public RelWriter explainTerms(RelWriter pw)

Description copied from class: AbstractRelNode

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

Overrides:

explainTerms in class BiRel

Parameters:

pw - Plan writer

Returns:

Plan writer for fluent-explain pattern

getCorrelationId

public CorrelationId getCorrelationId()

Returns the correlating expressions.

Returns:

correlating expressions

getCorrelVariable

public java.lang.String getCorrelVariable()

Description copied from interface: RelNode

Returns the name of the variable which is to be implicitly set at runtime each time a row is returned from the first input of this relational expression; or null if there is no variable.

Specified by:

getCorrelVariable in interface RelNode

Overrides:

getCorrelVariable in class AbstractRelNode

Returns:

Name of correlating variable, or null

getRequiredColumns

public ImmutableBitSet getRequiredColumns()

Returns the required columns in left relation required for the correlation in the right.

Returns:

columns in left relation required for the correlation in the right

getVariablesSet

public java.util.Set<CorrelationId> getVariablesSet()

Description copied from interface: RelNode

Returns the variables that are set in this relational expression but also used and therefore not available to parents of this relational expression.

Note: only Correlate should set variables.

Specified by:

getVariablesSet in interface RelNode

Overrides:

getVariablesSet in class AbstractRelNode

Returns:

Names of variables which are set in this relational expression

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)