com.bigdata.relation.rule.eval.Solution Maven / Gradle / Ivy

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/*

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     [email protected]

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

*/
/*
 * Created on Jun 24, 2008
 */

package com.bigdata.relation.rule.eval;

import java.io.Serializable;

import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IPredicate;
import com.bigdata.relation.IRelation;
import com.bigdata.relation.rule.IRule;

/**
 * Flyweight implementation.
 * 
 * @author Bryan Thompson
 * @version $Id$
 */
public class Solution implements ISolution, Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 5477431033714540993L;
    
    private final E e;
    private final IRule rule;
    private final IBindingSet bindingSet;
    
    /**
     * Constructs the element iff requested, saves the rule reference iff
     * requested, and clones and saves the bindingSet iff requested. The
     * requested behavior depends on {@link IJoinNexus#solutionFlags()}. When
     * requested, the element is created using
     * {@link IRelation#newElement(IPredicate, IBindingSet)} for the
     * {@link IRelation} that is named by the head of the rule.
     * 
     * @param e
     *            The element.
     * @param rule
     *            The rule.
     * @param bindingSet
     *            The binding set for this solution. If
     *            {@link IJoinNexus#BINDINGS} was specified, then the binding
     *            set will be cloned by this ctor.
     * 
     * @throws IllegalArgumentException
     *             if any parameter is null.
     */
    @SuppressWarnings("unchecked")
    public Solution(final IJoinNexus joinNexus, final IRule rule,
            final IBindingSet bindingSet) {
        
        if (joinNexus == null)
            throw new IllegalArgumentException();
        
        if (rule == null)
            throw new IllegalArgumentException();
        
        if (bindingSet == null)
            throw new IllegalArgumentException();

        final int flags = joinNexus.solutionFlags();

        if ((flags & IJoinNexus.ELEMENT) != 0) {

            /*
             * The relation is responsible for how the elements are materialized
             * from the bindings.
             * 
             * Note: Caching for this relation is very important!
             */

            // the head of the rule.
            final IPredicate head = rule.getHead();

            // the relation for the head of the rule.
            final IRelation relation = joinNexus.getHeadRelationView(head);

            // use the relation's element factory.
            this.e = (E) relation.newElement(head.args(), bindingSet); // TODO BOp.args() is not efficient!
            
//            // use the relation's element factory.
//            this.e = (E) relation.newElement(head, bindingSet);

        } else {

            this.e = null;

        }

        if ((flags & IJoinNexus.BINDINGS) != 0) {

            this.bindingSet = bindingSet.clone();

        } else {

            this.bindingSet = null;

        }

        if ((flags & IJoinNexus.RULE) != 0) {

            this.rule = rule;

        } else {

            this.rule = null;

        }

    }
    
    public E get() {
        
        return e;
        
    }

    public IRule getRule() {

        return rule;
        
    }

    public IBindingSet getBindingSet() {

        return bindingSet;
        
    }
    
    public String toString() {

        final StringBuilder sb = new StringBuilder();

        sb.append("Solution");

        sb.append("{ element=" + e);

        sb.append(", rule=" + rule);

        sb.append(", bindingSet=" + bindingSet);

        sb.append("}");

        return sb.toString();
        
    }
    
}