Package org.eclipse.rdf4j.query.algebra.evaluation.optimizer

Class QueryJoinOptimizer.JoinVisitor

java.lang.Object

org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor<RuntimeException>

org.eclipse.rdf4j.query.algebra.evaluation.optimizer.QueryJoinOptimizer.JoinVisitor

All Implemented Interfaces:

QueryModelVisitor<RuntimeException>

Enclosing class:

QueryJoinOptimizer

protected class QueryJoinOptimizer.JoinVisitor
extends AbstractSimpleQueryModelVisitor<RuntimeException>

This can be extended by subclasses to allow for adjustments to the optimization process.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	JoinVisitor()

Method Summary

Modifier and Type	Method	Description
protected <M extends Map<Var, Integer>> void	fillVarFreqMap(List<Var> varList, M varFreqMap)
protected int	getForeignVarFreq(List<Var> ownUnboundVars, Map<Var,Integer> varFreqMap)
protected <L extends List<TupleExpr>> L	getJoinArgs(TupleExpr tupleExpr, L joinArgs)
protected List<Var>	getStatementPatternVars(TupleExpr tupleExpr)
protected List<TupleExpr>	getSubSelects(List<TupleExpr> expressions)	This method returns all direct sub-selects in the given list of expressions.
protected double	getTupleExprCost(TupleExpr tupleExpr, Map<TupleExpr,Double> cardinalityMap, Map<TupleExpr,List<Var>> varsMap, Map<Var,Integer> varFreqMap)
protected List<Var>	getUnboundVars(List<Var> vars)
void	meet(Join node)
void	meet(LeftJoin leftJoin)
void	meet(StatementPattern node)
protected List<TupleExpr>	reorderSubselects(List<TupleExpr> subSelects)	Determines an optimal ordering of subselect join arguments, based on variable bindings.
protected TupleExpr	selectNextTupleExpr(List<TupleExpr> expressions, Map<TupleExpr,Double> cardinalityMap, Map<TupleExpr,List<Var>> varsMap, Map<Var,Integer> varFreqMap)	Selects from a list of tuple expressions the next tuple expression that should be evaluated.

Methods inherited from class org.eclipse.rdf4j.query.algebra.helpers.AbstractSimpleQueryModelVisitor

meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meet, meetBinaryTupleOperator, meetBinaryValueOperator, meetCompareSubQueryValueOperator, meetNAryValueOperator, meetOther, meetSubQueryValueOperator, meetUnaryTupleOperator, meetUnaryValueOperator, meetUnsupported, meetUpdateExpr

Methods inherited from class java.lang.Object

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

Constructor Details

JoinVisitor

protected JoinVisitor()

Method Details

meet

public void meet(LeftJoin leftJoin)

Specified by:

meet in interface QueryModelVisitor<RuntimeException>

Overrides:

meet in class AbstractSimpleQueryModelVisitor<RuntimeException>

meet

public void meet(StatementPattern node)
          throws RuntimeException

Specified by:

meet in interface QueryModelVisitor<RuntimeException>

Overrides:

meet in class AbstractSimpleQueryModelVisitor<RuntimeException>

Throws:

RuntimeException

meet

public void meet(Join node)

Specified by:

meet in interface QueryModelVisitor<RuntimeException>

Overrides:

meet in class AbstractSimpleQueryModelVisitor<RuntimeException>

getJoinArgs

protected <L extends List<TupleExpr>> L getJoinArgs(TupleExpr tupleExpr,
 L joinArgs)

getStatementPatternVars

protected List<Var> getStatementPatternVars(TupleExpr tupleExpr)

fillVarFreqMap

protected <M extends Map<Var,
Integer>> void fillVarFreqMap(List<Var> varList,
 M varFreqMap)

getSubSelects

protected List<TupleExpr> getSubSelects(List<TupleExpr> expressions)

This method returns all direct sub-selects in the given list of expressions.

This method is meant to be possible to override by subclasses.

Parameters:

expressions -

Returns:

reorderSubselects

protected List<TupleExpr> reorderSubselects(List<TupleExpr> subSelects)

Determines an optimal ordering of subselect join arguments, based on variable bindings. An ordering is considered optimal if for each consecutive element it holds that first of all its shared variables with all previous elements is maximized, and second, the union of all its variables with all previous elements is maximized.

Example: reordering

   [f] [a b c] [e f] [a d] [b e]
 

should result in:

   [a b c] [a d] [b e] [e f] [f]
 

Parameters:

subSelects - the original ordering of expressions

Returns:

the optimized ordering of expressions

selectNextTupleExpr

protected TupleExpr selectNextTupleExpr(List<TupleExpr> expressions,
 Map<TupleExpr,Double> cardinalityMap,
 Map<TupleExpr,List<Var>> varsMap,
 Map<Var,Integer> varFreqMap)

Selects from a list of tuple expressions the next tuple expression that should be evaluated. This method selects the tuple expression with highest number of bound variables, preferring variables that have been bound in other tuple expressions over variables with a fixed value.

getTupleExprCost

protected double getTupleExprCost(TupleExpr tupleExpr,
 Map<TupleExpr,Double> cardinalityMap,
 Map<TupleExpr,List<Var>> varsMap,
 Map<Var,Integer> varFreqMap)

getUnboundVars

protected List<Var> getUnboundVars(List<Var> vars)

getForeignVarFreq

protected int getForeignVarFreq(List<Var> ownUnboundVars,
 Map<Var,Integer> varFreqMap)