/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
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.sail;
import info.aduna.iteration.CloseableIteration;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import org.apache.log4j.Logger;
import org.openrdf.query.Binding;
import org.openrdf.query.BindingSet;
import org.openrdf.query.QueryEvaluationException;
import org.openrdf.query.QueryInterruptedException;
import org.openrdf.query.impl.MapBindingSet;
import com.bigdata.bop.IBindingSet;
import com.bigdata.bop.IConstant;
import com.bigdata.bop.IVariable;
import com.bigdata.bop.engine.QueryTimeoutException;
import com.bigdata.rdf.internal.IV;
import com.bigdata.rdf.model.BigdataValue;
import com.bigdata.util.InnerCause;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Converts a bigdata {@link ICloseableIterator} {@link IBindingSet}s containing
* either (a) {@link BigdataValue}s or (b) {@link IV}s having cached
* {@link BigdataValue}s into a Sesame 2 {@link CloseableIteration} visiting
* Sesame 2 {@link BindingSet}s containing {@link BigdataValue}s.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id: Bigdata2Sesame2BindingSetIterator.java 5021 2011-08-04
* 15:44:21Z thompsonbry $
* @param <E>
* The generic type of the thrown exception.
*/
public class Bigdata2Sesame2BindingSetIterator implements
CloseableIteration<BindingSet, QueryEvaluationException> {
final protected static Logger log = Logger
.getLogger(Bigdata2Sesame2BindingSetIterator.class);
/**
* The source iterator (will be closed when this iterator is closed).
*/
private final ICloseableIterator<IBindingSet> src;
private final BindingSet constants;
private volatile boolean open = true;
/** Pre-fetched result for {@link #next()}. */
private BindingSet next = null;
/**
*
* @param src
* The source iterator (will be closed when this iterator is
* closed). All bound values in the visited {@link IBindingSet}s
* MUST be either (a) {@link BigdataValue}s -or- (b) {@link IV}s
* having a cached {@link BigdataValue}.
*/
public Bigdata2Sesame2BindingSetIterator(
final ICloseableIterator<IBindingSet> src) {
this(src, null);
}
/**
*
* @param src
* The source iterator (will be closed when this iterator is
* closed). All bound values in the visited {@link IBindingSet}s
* MUST be {@link IV}s and those {@link IV}s MUST have their
* {@link BigdataValue}s cached.
* @param constants
* Optional constants to be united with the output solutions.
*/
public Bigdata2Sesame2BindingSetIterator(
final ICloseableIterator<IBindingSet> src,
final BindingSet constants) {
if (src == null)
throw new IllegalArgumentException();
this.src = src;
this.constants = constants;
}
/**
* {@inheritDoc}
*
* @see <a href="https://sourceforge.net/apps/trac/bigdata/ticket/503">
* Bigdata2Sesame2BindingSetIterator throws QueryEvaluationException
* were it should throw NoSuchElementException. </a>
*/
public boolean hasNext() throws QueryEvaluationException {
try {
if (!open) {
return false;
}
if (next != null) {
// already fetched.
return true;
}
if (!src.hasNext()) {
// Exhausted.
close();
return false;
}
final IBindingSet bset = src.next(); // fetch
next = getBindingSet(bset); // resolve.
return true;
} catch (Throwable t) {
if (!open) {
/**
* The iterator was concurrently closed. This often means that
* the connection guarding the query was concurrently closed, in
* which case it is possible for a concurrent writer to have
* triggered recycling (on the RWStore). Therefore, we want to
* ignore any thrown exception after the iterator was closed
* since a wide variety of problems could be triggered by
* reading against a commit point that had since been recycled.
* <p>
* Note: The logic to fetch the next result was moved into
* hasNext() in order to avoid doing any work in next(). Thus,
* if there is any problem resolving the next chunk of
* solutions, hasNext() will report [false] if the iterator was
* concurrently closed and otherwise will throw out the
* exception.
*
* @see <a
* href="https://sourceforge.net/apps/trac/bigdata/ticket/644"
* > Bigdata2Sesame2BindingSetIterator can fail to notice
* asynchronous close() </a>
*/
return false;
}
// Ensure closed.
try {
close();
} catch (Throwable t2) {
// Ignore.
}
// Wrap and rethrow.
if (InnerCause.isInnerCause(t, QueryTimeoutException.class)) {
/*
* Align with the openrdf API.
*/
throw new QueryInterruptedException(t);
} else {
throw new QueryEvaluationException(t);
}
}
}
public BindingSet next() throws QueryEvaluationException {
try {
if (!hasNext())
throw new NoSuchElementException();
final BindingSet tmp = next;
next = null;
return tmp;
} catch (NoSuchElementException t) {
/*
* Note: This exception should not be wrapped per the ticket above.
*/
throw t;
}
// } catch (Throwable t) {
//
// if (!open) {
// /**
// * The iterator was concurrently closed. This often means that
// * the connection guarding the query was concurrently closed, in
// * which case it is possible for a concurrent writer to have
// * triggered recycling (on the RWStore). Therefore, we want to
// * ignore any thrown exception after the iterator was closed
// * since a wide variety of problems could be triggered by
// * reading against a commit point that had since been recycled.
// *
// * @see <a
// * href="https://sourceforge.net/apps/trac/bigdata/ticket/644"
// * > Bigdata2Sesame2BindingSetIterator can fail to notice
// * asynchronous close() </a>
// */
// throw new NoSuchElementException();
// }
//
// if (InnerCause.isInnerCause(t, QueryTimeoutException.class)) {
//
// /*
// * Align with the openrdf API.
// */
//
// throw new QueryInterruptedException(t);
//
// } else {
//
// throw new QueryEvaluationException(t);
//
// }
//
// }
}
/**
* Aligns a bigdata {@link IBindingSet} with the Sesame 2 {@link BindingSet}.
*
* @param src
* A bigdata {@link IBindingSet} containing only
* {@link BigdataValue}s.
*
* @return The corresponding Sesame 2 {@link BindingSet}.
*
* @throws IllegalArgumentException
* if the argument is <code>null</code>.
* @throws ClassCastException
* if a bound value is not a {@link BigdataValue}.
*/
@SuppressWarnings("rawtypes")
private BindingSet getBindingSet(final IBindingSet src) {
if (src == null)
throw new IllegalArgumentException();
final int n = src.size();
final MapBindingSet bindingSet = new MapBindingSet(n /* capacity */);
final Iterator<Map.Entry<IVariable,IConstant>> itr = src.iterator();
while (itr.hasNext()) {
final Map.Entry<IVariable, IConstant> entry = itr.next();
final IVariable<?> v = entry.getKey();
final IConstant<?> c = entry.getValue();
final Object val = c.get();
final BigdataValue value;
if (val instanceof IV) {
/*
* The bound value is an IV. The IV MUST have the BigdataValue
* cached.
*/
value = ((IV) val).getValue();
} else {
// Otherwise the bound value must be a BigdataValue.
value = (BigdataValue) val;
}
bindingSet.addBinding(v.getName(), value);
}
if (constants != null) {
final Iterator<Binding> it = constants.iterator();
while (it.hasNext()) {
final Binding b = it.next();
bindingSet.addBinding(b.getName(), b.getValue());
}
}
return bindingSet;
}
/**
* @throws UnsupportedOperationException
*/
public void remove() throws QueryEvaluationException {
throw new UnsupportedOperationException();
}
public void close() throws QueryEvaluationException {
if (open) {
open = false;
src.close();
}
}
}