Class LogicalOpMultiwayLeftJoin

java.lang.Object

se.liu.ida.hefquin.engine.queryplan.logical.impl.BaseForLogicalOps

se.liu.ida.hefquin.engine.queryplan.logical.impl.LogicalOpMultiwayLeftJoin

All Implemented Interfaces:

QueryPlanOperator, LogicalOperator, NaryLogicalOp

public class LogicalOpMultiwayLeftJoin
extends BaseForLogicalOps
implements NaryLogicalOp

A multiway left join corresponds to a sequence of SPARQL OPTIONAL clauses. Hence, it is not to be confused with nested OPTIONAL clauses (which would, instead, be captured as multiple nested multiway left joins).

Field Summary

Fields

Modifier and Type	Field	Description
protected static final LogicalOpMultiwayLeftJoin	singletonThatMayReduce
protected static final LogicalOpMultiwayLeftJoin	singletonWithoutReduction

Fields inherited from class se.liu.ida.hefquin.engine.queryplan.logical.impl.BaseForLogicalOps

mayReduce

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	LogicalOpMultiwayLeftJoin(boolean mayReduce)

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object o)
ExpectedVariables	getExpectedVariables(ExpectedVariables... inputVars)	Returns the variables that can be expected in the solution mappings produced by this operator in the case that the input(s) to this operator contain solutions mappings with the given set(s) of variables.
static LogicalOpMultiwayLeftJoin	getInstance()	Returns the singleton instance of LogicalOpMultiwayLeftJoin that does not reduce duplicates.
static LogicalOpMultiwayLeftJoin	getInstance(boolean mayReduce)
int	hashCode()
String	toString()
void	visit(LogicalPlanVisitor visitor)

Methods inherited from class se.liu.ida.hefquin.engine.queryplan.logical.impl.BaseForLogicalOps

mayReduce

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface se.liu.ida.hefquin.engine.queryplan.logical.LogicalOperator

mayReduce

Field Details

singletonWithoutReduction

protected static final LogicalOpMultiwayLeftJoin singletonWithoutReduction

singletonThatMayReduce

protected static final LogicalOpMultiwayLeftJoin singletonThatMayReduce

Constructor Details

LogicalOpMultiwayLeftJoin

protected LogicalOpMultiwayLeftJoin(boolean mayReduce)

Method Details

getInstance

public static LogicalOpMultiwayLeftJoin getInstance(boolean mayReduce)

getInstance

public static LogicalOpMultiwayLeftJoin getInstance()

Returns the singleton instance of LogicalOpMultiwayLeftJoin that does not reduce duplicates.

This is equivalent to calling getInstance(boolean) with the argument false.

Returns:

the singleton instance that does not reduce duplicates

getExpectedVariables

public ExpectedVariables getExpectedVariables(ExpectedVariables... inputVars)

Description copied from interface: QueryPlanOperator

Returns the variables that can be expected in the solution mappings produced by this operator in the case that the input(s) to this operator contain solutions mappings with the given set(s) of variables. The number of ExpectedVariables objects passed to this method must be in line with the degree of this operator (e.g., for a unary operator, exactly one such object must be passed).

Specified by:

getExpectedVariables in interface QueryPlanOperator

visit

public void visit(LogicalPlanVisitor visitor)

Specified by:

visit in interface LogicalOperator

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object