org.modeshape.graph.query.optimize
Class RewriteAsRangeCriteria

java.lang.Object
  org.modeshape.graph.query.optimize.RewriteAsRangeCriteria

All Implemented Interfaces:

OptimizerRule

@Immutable
public class RewriteAsRangeCriteria
extends Object
implements OptimizerRule

An optimizer rule that rewrites two AND-ed Constraints that constraint a dynamic operand to a range of values as a single Between constraint. This rule also collapses and removes any constraints that are unnecessary because other constraints are more restrictive or because they cancel out other constraints.

Field Summary

protected static Constraint	CONFLICTING_CONSTRAINT
static RewriteAsRangeCriteria	INSTANCE

Constructor Summary

RewriteAsRangeCriteria()

Method Summary

protected int	compareStaticOperands(QueryContext context, Comparison comparison1, Comparison comparison2) Compare the values used in the two comparisons
PlanNode	execute(QueryContext context, PlanNode plan, LinkedList<OptimizerRule> ruleStack) Optimize the supplied plan using the supplied context, hints, and yet-to-be-run rules.
protected Comparison	getComparison(QueryContext context, Comparison comparison1, Comparison comparison2, boolean smallest) Get the comparison with the smallest (or largest) value.
protected Object	getValue(QueryContext context, StaticOperand operand) Get the value associated with the static operand of the comparison.
protected void	nullReference(List<Comparison> comparisons, Comparison comparisonToNull) Find all occurrences of the comparison object in the supplied list and null the list's reference to it.
protected void	nullReference(List<Comparison> comparisons, Iterable<Comparison> comparisonsToNull) Find all references in the supplied list that match those supplied and set them to null.
protected Constraint	rewrite(QueryContext context, List<Comparison> comparisons) Rewrite the supplied comparisons, returning the new constraint and nulling in the supplied list those comparisons that were rewritten (and leaving those that were not rewritten)
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

CONFLICTING_CONSTRAINT

protected static final Constraint CONFLICTING_CONSTRAINT

INSTANCE

public static final RewriteAsRangeCriteria INSTANCE

Constructor Detail

RewriteAsRangeCriteria

public RewriteAsRangeCriteria()

Method Detail

execute

public PlanNode execute(QueryContext context,
                        PlanNode plan,
                        LinkedList<OptimizerRule> ruleStack)

Optimize the supplied plan using the supplied context, hints, and yet-to-be-run rules.

Specified by:

execute in interface OptimizerRule

Parameters:

context - the context in which the query is being optimized; never null

plan - the plan to be optimized; never null

ruleStack - the stack of rules that will be run after this rule; never null

Returns:

the optimized plan; never null

See Also:

OptimizerRule.execute(org.modeshape.graph.query.QueryContext, org.modeshape.graph.query.plan.PlanNode, java.util.LinkedList)

toString

public String toString()

Overrides:

toString in class Object

See Also:

Object.toString()

rewrite

protected Constraint rewrite(QueryContext context,
                             List<Comparison> comparisons)

Rewrite the supplied comparisons, returning the new constraint and nulling in the supplied list those comparisons that were rewritten (and leaving those that were not rewritten)

Parameters:

context - the query context

comparisons - the list of comparisons that sould be rewritten if possible; never null

Returns:

the rewritten constraint, or null if no comparisons were rewritten

nullReference

protected void nullReference(List<Comparison> comparisons,
                             Comparison comparisonToNull)

Find all occurrences of the comparison object in the supplied list and null the list's reference to it.

Parameters:

comparisons - the collection in which null references are to be placed

comparisonToNull - the comparison that is to be found and nulled in the collection

nullReference

protected void nullReference(List<Comparison> comparisons,
                             Iterable<Comparison> comparisonsToNull)

Find all references in the supplied list that match those supplied and set them to null.

Parameters:

comparisons - the collection in which null references are to be placed

comparisonsToNull - the comparisons that are to be found and nulled in the collection

compareStaticOperands

protected int compareStaticOperands(QueryContext context,
                                    Comparison comparison1,
                                    Comparison comparison2)

Compare the values used in the two comparisons

Parameters:

context - the query context; may not be null

comparison1 - the first comparison object; may not be null

comparison2 - the second comparison object; may not be null

Returns:

0 if the values are the same, less than 0 if the first comparison's value is less than the second's, or greater than 0 if the first comparison's value is greater than the second's

getComparison

protected Comparison getComparison(QueryContext context,
                                   Comparison comparison1,
                                   Comparison comparison2,
                                   boolean smallest)

Get the comparison with the smallest (or largest) value.

Parameters:

context - the query context; may not be null

comparison1 - the first comparison object; may not be null

comparison2 - the second comparison object; may not be null

smallest - true if the comparison with the smallest value should be returned, or false otherwise

Returns:

the comparison with the smallest (or largest) value

getValue

protected Object getValue(QueryContext context,
                          StaticOperand operand)

Get the value associated with the static operand of the comparison. If the operand is a variable name, the variable value is returned.

Parameters:

context - the query context; may not be null

operand - the static operand; may not be null

Returns:

the value of the static operand