com.bigdata.rdf.sparql.ast

Class FunctionRegistry.ExistsFactory

java.lang.Object

com.bigdata.rdf.sparql.ast.FunctionRegistry.ExistsFactory

All Implemented Interfaces:

FunctionRegistry.Factory

Enclosing class:

FunctionRegistry

public static class FunctionRegistry.ExistsFactory
extends Object
implements FunctionRegistry.Factory

Factory for EXISTS() and NOT EXISTS(). The EXISTS() node in the AST must be marked with the group graph pattern as an annotation. The FunctionNode will be a simple test of an anonymous variable. EXISTS tests the variable for true. Not exists tests the variable for false. The name of that anonymous variable is the sole ValueExpressionNode passed into this factory.

The "guts" of the EXISTS logic is translated by an IASTOptimizer into an ASK subquery (an instance of SubqueryRoot). This will be executed as a special BOp that bind the success or failure of that ASK subquery on the anonymous variable. The "ASK" subquery does not fail, it just binds the truth state of the ASK subquery on the anonymous variable. The IValueExpression returned by this factory just tests the truth state of that anonymous variable.

Constructor Summary

Constructors

Constructor and Description
FunctionRegistry.ExistsFactory(boolean exists)

Method Summary

Methods

Modifier and Type	Method and Description
IValueExpression<? extends IV>	create(BOpContextBase context, GlobalAnnotations globals, Map<String,Object> scalarValues, ValueExpressionNode... args) Create an IValueExpression instance.

Methods inherited from class java.lang.Object

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

Constructor Detail

FunctionRegistry.ExistsFactory

public FunctionRegistry.ExistsFactory(boolean exists)

Method Detail

create

public IValueExpression<? extends IV> create(BOpContextBase context,
                                    GlobalAnnotations globals,
                                    Map<String,Object> scalarValues,
                                    ValueExpressionNode... args)

Description copied from interface: FunctionRegistry.Factory

Create an IValueExpression instance.

Specified by:

create in interface FunctionRegistry.Factory

Parameters:

context - The BOpContextBase required to evaluate IValueExpressions. This is used if we need to statically evaluate an IValueExpression during query optimization. During query execution the ContextBindingSet will convey this information.

globals - The global annotations, including the lexicon namespace.

scalarValues - The scalar arguments (used by some IAggregates).

args - The function arguments.

Returns:

The IValueExpression.

See Also:

create() was refactored to pass in the {@link BOpContextBase} to allow correct resolution of the {@link LexiconRelation} and {@link ILexiconConfiguration} in order to properly evaluate {@link IValueExpression}s during query optimization.