org.eigenbase.rel
Class AbstractRelNode

java.lang.Object
  org.eigenbase.rel.AbstractRelNode

All Implemented Interfaces:

Cloneable, RelNode

Direct Known Subclasses:

EmptyRel, FennelDoubleRel, FennelMultipleRel, HepRelVertex, JdbcQuery, JoinRelBase, MultiJoinRel, OneRowRelBase, RelSubset, SetOpRel, SingleRel, TableAccessRelBase, TableFunctionRelBase, ValuesRelBase, VolcanoPlannerTest.TestLeafRel, VolcanoPlannerTraitTest.TestLeafRel

public abstract class AbstractRelNode
extends Object
implements RelNode

Base class for every relational expression (RelNode).

Field Summary

private RelOptCluster	cluster
private String	correlVariable The variable by which to refer to rows from this relational expression, as correlating expressions; null if this expression is not correlated on.
private String	desc Description, consists of id plus digest.
protected String	digest A short description of this relational expression's type, inputs, and other properties.
protected int	id unique id of this object -- for debugging
(package private) static int	nextId generator for id values
protected RelDataType	rowType Cached type of this relational expression.
private static Logger	tracer
protected RelTraitSet	traits The RelTraitSet that describes the traits of this RelNode.

Fields inherited from interface org.eigenbase.rel.RelNode

emptyArray

Constructor Summary

AbstractRelNode(RelOptCluster cluster, RelTraitSet traits)
Creates a AbstractRelNode.

Method Summary

void	childrenAccept(RelVisitor visitor) Interacts with the RelVisitor in a visitor pattern to traverse the tree of relational expressions.
abstract RelNode	clone() Clones this RelNode.
RelTraitSet	cloneTraits() Returns a clone of this RelNode's traits.
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).
protected RelDataType	deriveRowType()
void	explain(RelOptPlanWriter pw)
RexNode[]	getChildExps() Returns an array of this relational expression's child expressions (not including the inputs returned by RelNode.getInputs().
RelOptCluster	getCluster() Returns the cluster this relational expression belongs to.
List<RelCollation>	getCollationList() Returns a description of the physical ordering (or orderings) of this relational expression.
CallingConvention	getConvention() Return the CallingConvention trait from this RelNode's trait set.
String	getCorrelVariable() Returns the name of the variable which is to be implicitly set at runtime each time a row is returned from this relational expression; or null if there is no variable.
String	getDescription() Returns a string which describes the relational expression and, unlike RelNode.getDigest(), also includes the identity.
String	getDigest() Returns a string which concisely describes the definition of this relational expression.
RelDataType	getExpectedInputRowType(int ordinalInParent) Returns the type of the rows expected for an input.
int	getId() Returns the ID of this relational expression, unique among all relational expressions created since the server was started.
RelNode	getInput(int i) Returns the ith input relational expression.
RelNode[]	getInputs() Returns an array of this relational expression's inputs.
String	getOrCreateCorrelVariable() Returns a variable with which to reference the current row of this relational expression as a correlating variable.
RelOptQuery	getQuery() Returns the sub-query this relational expression belongs to.
String	getRelTypeName() Returns the name of this relational expression's class, sans package name, for use in RelNode.explain(org.eigenbase.relopt.RelOptPlanWriter).
double	getRows() Returns an estimate of the number of rows this relational expression will return.
RelDataType	getRowType() Returns the type of the rows returned by this relational expression.
RelOptTable	getTable() If this relational expression represents an access to a table, returns that table, otherwise returns null.
RelTraitSet	getTraits() Retrieves this RelNode's traits.
Set<String>	getVariablesStopped() Returns the names of variables which are set in this relational expression but also used and therefore not available to parents of this relational expression.
<T extends AbstractRelNode> T	inheritTraitsFrom(T rel) Sets this relational expression's traits to the same as another relational expression.
boolean	isAccessTo(RelOptTable table) Returns whether this relational expression is an access to table.
boolean	isDistinct() Returns whether the same value will not come out twice.
boolean	isValid(boolean fail) Returns whether this relational expression is valid.
void	onRegister(RelOptPlanner planner) Receives notification that this expression is about to be registered.
String	recomputeDigest() Computes the digest, assigns it, and returns it.
static void	register(RelOptPlanner planner) Registers any special rules specific to this kind of relational expression.
void	registerCorrelVariable(String correlVariable) Registers a correlation variable.
void	replaceInput(int ordinalInParent, RelNode p) Replaces the ordinalInParentth input.
void	setCorrelVariable(String correlVariable) Sets the name of the variable which is to be implicitly set at runtime each time a row is returned from this relational expression
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

nextId

static int nextId

generator for id values

tracer

private static final Logger tracer

desc

private String desc

Description, consists of id plus digest.

rowType

protected RelDataType rowType

Cached type of this relational expression.

digest

protected String digest

A short description of this relational expression's type, inputs, and other properties. The string uniquely identifies the node; another node is equivalent if and only if it has the same value. Computed by computeDigest(), assigned by onRegister(org.eigenbase.relopt.RelOptPlanner), returned by getDigest().

See Also:

desc

cluster

private RelOptCluster cluster

id

protected int id

unique id of this object -- for debugging

correlVariable

private String correlVariable

The variable by which to refer to rows from this relational expression, as correlating expressions; null if this expression is not correlated on.

traits

protected RelTraitSet traits

The RelTraitSet that describes the traits of this RelNode.

Constructor Detail

AbstractRelNode

public AbstractRelNode(RelOptCluster cluster,
                       RelTraitSet traits)

Creates a AbstractRelNode.

"Precondition:"

cluster != null

Method Detail

clone

public abstract RelNode clone()

Description copied from interface: RelNode

Clones this RelNode.

Traits of the RelNode must be explicitly cloned, using inheritTraitsFrom(AbstractRelNode), as the RelNode may have traits of which it has no knowledge. Example implementation:

     public MyRelNode clone()
     {
         MyRelNode clone = new MyRelNode(...);
         clone.inheritTraitsFrom(this);
         return clone;
     }
 

N.B.: This method must be overridden whenever an existing, concrete RelNode is extended. Otherwise, calling clone() will produce a differently typed RelNode, resulting in invalid or incorrect query plans.

Specified by:

clone in interface RelNode

Overrides:

clone in class Object

Returns:

a clone of this RelNode

isAccessTo

public boolean isAccessTo(RelOptTable table)

Description copied from interface: RelNode

Returns whether this relational expression is an access to table.

Specified by:

isAccessTo in interface RelNode

getChildExps

public RexNode[] getChildExps()

Description copied from interface: RelNode

Returns an array of this relational expression's child expressions (not including the inputs returned by RelNode.getInputs(). If there are no child expressions, returns an empty array, not null.

Specified by:

getChildExps in interface RelNode

getCluster

public RelOptCluster getCluster()

Description copied from interface: RelNode

Returns the cluster this relational expression belongs to.

Specified by:

getCluster in interface RelNode

Returns:

cluster

getConvention

public final CallingConvention getConvention()

Description copied from interface: RelNode

Return the CallingConvention trait from this RelNode's trait set.

Specified by:

getConvention in interface RelNode

Returns:

this RelNode's CallingConvention

getTraits

public RelTraitSet getTraits()

Description copied from interface: RelNode

Retrieves this RelNode's traits. Note that although the RelTraitSet returned is modifiable, it must not be modified during optimization. It is legal to modify the traits of a RelNode before or after optimization, although doing so could render a tree of RelNodes unimplementable. If a RelNode's traits need to be modified during optimization, clone the RelNode and change the clone's traits.

Specified by:

getTraits in interface RelNode

Returns:

this RelNode's trait set

cloneTraits

public RelTraitSet cloneTraits()

Returns a clone of this RelNode's traits. Useful for implementing clone().

Returns:

a clone of this RelNode's traits.

inheritTraitsFrom

public <T extends AbstractRelNode> T inheritTraitsFrom(T rel)

Sets this relational expression's traits to the same as another relational expression. The other relational expression must be the same type as this.

The typical use of this method is in the implementation of a clone() method:

class MyRel { public MyRel clone() { return new MyRel( getCluster(), getChild().clone(), fieldX.clone(), fieldY.clone()) .inheritTraitsFrom(this); } }

To enable calls to be chained in this way, this method returns this as a convenience.

Parameters:

rel - Relational expression whose traits to copy

Returns:

This relational expression

setCorrelVariable

public void setCorrelVariable(String correlVariable)

Description copied from interface: RelNode

Sets the name of the variable which is to be implicitly set at runtime each time a row is returned from this relational expression

Specified by:

setCorrelVariable in interface RelNode

Parameters:

correlVariable - Name of correlating variable

getCorrelVariable

public 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 this relational expression; or null if there is no variable.

Specified by:

getCorrelVariable in interface RelNode

Returns:

Name of correlating variable, or null

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

getId

public int getId()

Description copied from interface: RelNode

Returns the ID of this relational expression, unique among all relational expressions created since the server was started.

Specified by:

getId in interface RelNode

Returns:

Unique ID

getInput

public RelNode getInput(int i)

Description copied from interface: RelNode

Returns the i^th input relational expression.

Specified by:

getInput in interface RelNode

Parameters:

i - Ordinal of input

Returns:

i^th input

getOrCreateCorrelVariable

public String getOrCreateCorrelVariable()

Description copied from interface: RelNode

Returns a variable with which to reference the current row of this relational expression as a correlating variable. Creates a variable if none exists.

Specified by:

getOrCreateCorrelVariable in interface RelNode

getQuery

public RelOptQuery getQuery()

Description copied from interface: RelNode

Returns the sub-query this relational expression belongs to. A sub-query determines the scope for correlating variables (see RelNode.setCorrelVariable(String)).

Specified by:

getQuery in interface RelNode

Returns:

Sub-query

register

public static void register(RelOptPlanner planner)

Registers any special rules specific to this kind of relational expression.

The planner calls this method this first time that it sees a relational expression of this class. The derived class should call RelOptPlanner.addRule(org.eigenbase.relopt.RelOptRule) for each rule, and then call register(org.eigenbase.relopt.RelOptPlanner) on its base class.

getRelTypeName

public final String getRelTypeName()

Description copied from interface: RelNode

Returns the name of this relational expression's class, sans package name, for use in RelNode.explain(org.eigenbase.relopt.RelOptPlanWriter). For example, for a org.eigenbase.rel.ArrayRel.ArrayReader, this method returns "ArrayReader".

Specified by:

getRelTypeName in interface RelNode

isValid

public boolean isValid(boolean fail)

Description copied from interface: RelNode

Returns whether this relational expression is valid.

If assertions are enabled, this method is typically called with fail = true, as follows:

assert rel.isValid(true)

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

Specified by:

isValid in interface RelNode

Parameters:

fail - Whether to fail if invalid

Returns:

Whether relational expression is valid

getCollationList

public List<RelCollation> getCollationList()

Description copied from interface: RelNode

Returns a description of the physical ordering (or orderings) of this relational expression.

Specified by:

getCollationList in interface RelNode

getRowType

public final RelDataType getRowType()

Description copied from interface: RelNode

Returns the type of the rows returned by this relational expression.

Specified by:

getRowType in interface RelNode

deriveRowType

protected RelDataType deriveRowType()

getExpectedInputRowType

public RelDataType getExpectedInputRowType(int ordinalInParent)

Description copied from interface: RelNode

Returns the type of the rows expected for an input. Defaults to RelNode.getRowType().

Specified by:

getExpectedInputRowType in interface RelNode

Parameters:

ordinalInParent - input's 0-based ordinal with respect to this parent rel

Returns:

expected row type

getInputs

public RelNode[] getInputs()

Description copied from interface: RelNode

Returns an array of this relational expression's inputs. If there are no inputs, returns an empty array, not null.

Specified by:

getInputs in interface RelNode

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.eigenbase.rel.RelNode), which gives plugins a chance to override the rel's default ideas about row count.

Specified by:

getRows in interface RelNode

getVariablesStopped

public Set<String> getVariablesStopped()

Description copied from interface: RelNode

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

By default, returns the empty set. Derived classes may override this method.

Specified by:

getVariablesStopped in interface RelNode

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

Parameters:

variableSet - receives variables used

collectVariablesSet

public void collectVariablesSet(Set<String> variableSet)

Description copied from interface: RelNode

Collects variables set by this expression.

Specified by:

collectVariablesSet in interface RelNode

Parameters:

variableSet - receives variables known to be set by

childrenAccept

public void childrenAccept(RelVisitor visitor)

Description copied from interface: RelNode

Interacts with the RelVisitor in a visitor pattern to traverse the tree of relational expressions.

Specified by:

childrenAccept in interface RelNode

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.eigenbase.rel.RelNode), which gives plugins a chance to override the rel's default ideas about cost.

Specified by:

computeSelfCost in interface RelNode

explain

public void explain(RelOptPlanWriter pw)

Specified by:

explain in interface RelNode

onRegister

public void onRegister(RelOptPlanner planner)

Description copied from interface: RelNode

Receives notification that this expression is about to be registered. The implementation of this method must at least register all child expressions.

Specified by:

onRegister in interface RelNode

recomputeDigest

public String recomputeDigest()

Description copied from interface: RelNode

Computes the digest, assigns it, and returns it. For planner use only.

Specified by:

recomputeDigest in interface RelNode

registerCorrelVariable

public void registerCorrelVariable(String correlVariable)

Description copied from interface: RelNode

Registers a correlation variable.

Specified by:

registerCorrelVariable in interface RelNode

See Also:

RelNode.getVariablesStopped()

replaceInput

public void replaceInput(int ordinalInParent,
                         RelNode p)

Description copied from interface: RelNode

Replaces the ordinalInParent^th input. You must override this method if you override RelNode.getInputs().

Specified by:

replaceInput in interface RelNode

toString

public String toString()

Overrides:

toString in class Object

getDescription

public final String getDescription()

Description copied from interface: RelNode

Returns a string which describes the relational expression and, unlike RelNode.getDigest(), also includes the identity. Typically returns "rel#{id}:{digest}".

Specified by:

getDescription in interface RelNode

getDigest

public final String getDigest()

Description copied from interface: RelNode

Returns a string which concisely describes the definition of this relational expression. Two relational expressions are equivalent if and only if their digests are the same.

The digest does not contain the relational expression's identity -- that would prevent similar relational expressions from ever comparing equal -- but does include the identity of children (on the assumption that children have already been normalized).

If you want a descriptive string which contains the identity, call Object.toString(), which always returns "rel#{id}:{digest}".

Specified by:

getDigest in interface RelNode

getTable

public RelOptTable getTable()

Description copied from interface: RelNode

If this relational expression represents an access to a table, returns that table, otherwise returns null.

Specified by:

getTable in interface RelNode

computeDigest

protected String computeDigest()

Computes the digest. Does not modify this object.

"Postcondition:"

return != null