com.bigdata.rdf.internal.constraints.SPARQLConstraint 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

*/
package com.bigdata.rdf.internal.constraints;

import java.util.Map;

import org.apache.log4j.Logger;

import com.bigdata.bop.BOp;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IValueExpression;
import com.bigdata.rdf.error.SparqlTypeErrorException;
import com.bigdata.rdf.internal.IV;
import com.bigdata.rdf.internal.impl.literal.XSDBooleanIV;
import com.bigdata.rdf.sparql.ast.FilterNode;
import com.bigdata.util.InnerCause;

/**
 * BOpConstraint that wraps a {@link EBVBOp}, which itself computes the 
 * effective boolean value of an {@link IValueExpression}.
 */
@SuppressWarnings("rawtypes")
public class SPARQLConstraint extends
        com.bigdata.bop.constraint.Constraint {

	/**
	 * 
	 */
	private static final long serialVersionUID = -5796492538735372727L;
	
    private static final transient Logger log = Logger
            .getLogger(SPARQLConstraint.class);

	/**
	 * The operand of this operator must evaluate to a boolean. If the operand
	 * is not known to evaluate to a boolean, wrap it with an {@link EBVBOp}.
	 */
	private static XSDBooleanIVValueExpression wrap(
			final IValueExpression ve) {
		
        return ve instanceof XSDBooleanIVValueExpression ? 
        		(XSDBooleanIVValueExpression) ve : new EBVBOp(ve);

	}
	
	/**
	 * Construct a SPARQL constraint using the specified value expression.
	 * The value expression will be automatically wrapped inside an
	 * {@link EBVBOp} if it does not itself evaluate to a boolean.
	 */
    public SPARQLConstraint(final IValueExpression x) {

		this(new BOp[] { wrap(x) }, null/*annocations*/);
		
    }

    /**
     * Required shallow copy constructor.
     */
    public SPARQLConstraint(final BOp[] args, final Map anns) {

        super(args, anns);

        if (args.length != 1 || args[0] == null)
            throw new IllegalArgumentException();
        
    }

    /**
     * Constructor required for {@link com.bigdata.bop.BOpUtility#deepCopy(FilterNode)}.
     */
    public SPARQLConstraint(final SPARQLConstraint op) {

        super(op);

    }

    @SuppressWarnings("unchecked")
    @Override
    public IValueExpression get(final int i) {

        return (IValueExpression) super.get(i);
        
    }
    
//    public IValueExpression getValueExpression() {
//        return (IValueExpression) get(0);
//    }
    	
    @Override
	public boolean accept(final IBindingSet bs) {

		try {

			// evaluate the EBV operator
            final XSDBooleanIV iv = get(0).get(bs);
			
			return iv.booleanValue();

		} catch (Throwable t) {

			if (InnerCause.isInnerCause(t, SparqlTypeErrorException.class)) {

				// trap the type error and filter out the solution
				if (log.isInfoEnabled())
					log.info("discarding solution due to type error: " + bs
							+ " : " + t);

				return false;

			}

			throw new RuntimeException(t);

		}

	}

    /**
     * Overridden to provide a little bit of information about the attached
     * constraint.
     */
    @Override
    public String toShortString() {

        return super.toShortString() + "{condition="
                + getValueExpression().toShortString() + "}";

    }

}