SingletonSet.java

/*******************************************************************************
 * Copyright (c) 2015 Eclipse RDF4J contributors, Aduna, and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Distribution License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *******************************************************************************/
package org.eclipse.rdf4j.query.algebra;

import java.util.Collections;
import java.util.Set;

import org.eclipse.rdf4j.common.order.AvailableStatementOrder;

/**
 * A tuple expression that contains exactly one solution with zero bindings.
 */
public class SingletonSet extends AbstractQueryModelNode implements TupleExpr {

	@Override
	public Set<String> getBindingNames() {
		return getAssuredBindingNames();
	}

	@Override
	public Set<String> getAssuredBindingNames() {
		return Collections.emptySet();
	}

	@Override
	public <X extends Exception> void visit(QueryModelVisitor<X> visitor) throws X {
		visitor.meet(this);
	}

	@Override
	public <X extends Exception> void visitChildren(QueryModelVisitor<X> visitor) throws X {
		// no-op
	}

	@Override
	public void replaceChildNode(QueryModelNode current, QueryModelNode replacement) {
		throw new IllegalArgumentException("Node is not a child node: " + current);
	}

	@Override
	public boolean equals(Object other) {
		return other instanceof SingletonSet;
	}

	@Override
	public int hashCode() {
		return "SingletonSet".hashCode();
	}

	@Override
	public SingletonSet clone() {
		return (SingletonSet) super.clone();
	}

	@Override
	public Set<Var> getSupportedOrders(AvailableStatementOrder tripleSource) {
		return Set.of();
	}

	@Override
	public void setOrder(Var var) {
		throw new UnsupportedOperationException("This TupleExpr does not support ordering");
	}

	@Override
	public Var getOrder() {
		throw new UnsupportedOperationException("This TupleExpr does not support ordering");
	}
}