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ARQ is a SPARQL 1.1 query engine for Apache Jena
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.sparql.engine;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import org.apache.jena.atlas.lib.Alarm ;
import org.apache.jena.atlas.lib.AlarmClock;
import org.apache.jena.atlas.logging.Log;
import org.apache.jena.graph.Node;
import org.apache.jena.graph.Triple;
import org.apache.jena.query.* ;
import org.apache.jena.rdf.model.* ;
import org.apache.jena.riot.system.IRIResolver;
import org.apache.jena.shared.PrefixMapping;
import org.apache.jena.sparql.ARQConstants;
import org.apache.jena.sparql.core.DatasetGraph;
import org.apache.jena.sparql.core.Quad;
import org.apache.jena.sparql.core.describe.DescribeHandler;
import org.apache.jena.sparql.core.describe.DescribeHandlerRegistry;
import org.apache.jena.sparql.engine.binding.Binding;
import org.apache.jena.sparql.engine.binding.BindingRoot;
import org.apache.jena.sparql.engine.binding.BindingUtils;
import org.apache.jena.sparql.engine.iterator.QueryIteratorWrapper;
import org.apache.jena.sparql.graph.GraphFactory;
import org.apache.jena.sparql.modify.TemplateLib;
import org.apache.jena.sparql.syntax.ElementGroup;
import org.apache.jena.sparql.syntax.Template;
import org.apache.jena.sparql.util.Context;
import org.apache.jena.sparql.util.DatasetUtils;
import org.apache.jena.sparql.util.ModelUtils;
/** All the SPARQL query result forms made from a graph-level execution object */
public class QueryExecutionBase implements QueryExecution
{
private Query query;
private Dataset dataset;
private QueryEngineFactory qeFactory;
private QueryIterator queryIterator = null;
private Plan plan = null;
private Context context;
private QuerySolution initialBinding = null;
// Set if QueryIterator.cancel has been called
private volatile boolean isCancelled = false;
private boolean closed;
private volatile TimeoutCallback expectedCallback = null;
private Alarm timeout1Alarm = null;
private Alarm timeout2Alarm = null;
// synchronization.
private final Object lockTimeout = new Object();
private static final long TIMEOUT_UNSET = -1;
private static final long TIMEOUT_INF = -2;
private long timeout1 = TIMEOUT_UNSET;
private long timeout2 = TIMEOUT_UNSET;
private final AlarmClock alarmClock = AlarmClock.get();
public QueryExecutionBase(Query query, Dataset dataset,
Context context, QueryEngineFactory qeFactory) {
this.query = query;
this.dataset = dataset ;
this.context = context ;
this.qeFactory = qeFactory ;
init() ;
}
private void init() {
DatasetGraph dsg = (dataset == null) ? null : dataset.asDatasetGraph() ;
context = Context.setupContext(context, dsg) ;
if ( query != null )
context.put(ARQConstants.sysCurrentQuery, query) ;
// NB: Setting timeouts via the context after creating a QueryExecutionBase
// will not work. But we can't move it until the point the execution starts because of
// get and set timeout operations on this object.
setAnyTimeouts() ;
}
private void setAnyTimeouts() {
if ( context.isDefined(ARQ.queryTimeout) ) {
Object obj = context.get(ARQ.queryTimeout);
if ( obj instanceof Number ) {
long x = ((Number)obj).longValue();
setTimeout(x);
} else if ( obj instanceof String ) {
try {
String str = obj.toString();
if ( str.contains(",") ) {
String[] a = str.split(",");
long x1 = Long.parseLong(a[0]);
long x2 = Long.parseLong(a[1]);
setTimeout(x1, x2);
} else {
long x = Long.parseLong(str);
setTimeout(x);
}
}
catch (RuntimeException ex) {
Log.warn(this, "Can't interpret string for timeout: " + obj);
}
} else
Log.warn(this, "Can't interpret timeout: " + obj);
}
}
@Override
public void close() {
closed = true;
if ( queryIterator != null )
queryIterator.close() ;
if ( plan != null )
plan.close() ;
if ( timeout1Alarm != null )
alarmClock.cancel(timeout1Alarm) ;
if ( timeout2Alarm != null )
alarmClock.cancel(timeout2Alarm) ;
}
@Override
public boolean isClosed() {
return closed ;
}
private void checkNotClosed() {
if ( closed )
throw new QueryExecException("HTTP QueryExecution has been closed") ;
}
@Override
public void abort() {
synchronized (lockTimeout) {
// This is called asynchronously to the execution.
// synchronized is for coordination with other calls of
// .abort and with the timeout2 reset code.
if ( queryIterator != null )
// we notify the chain of iterators,
// however, we do *not* close the
// iterators.
// That happens after the cancellation
// is properly over.
queryIterator.cancel();
isCancelled = true;
}
}
@Override
public ResultSet execSelect() {
checkNotClosed();
if ( !query.isSelectType() )
throw new QueryExecException("Attempt to have ResultSet from a " + labelForQuery(query) + " query");
ResultSet rs = execResultSet();
return new ResultSetCheckCondition(rs, this);
}
// Construct
@Override
public Model execConstruct() {
return execConstruct(GraphFactory.makeJenaDefaultModel());
}
@Override
public Model execConstruct(Model model) {
checkNotClosed();
try {
Iterator it = execConstructTriples();
// Prefixes for result
insertPrefixesInto(model);
while (it.hasNext()) {
Triple t = it.next();
Statement stmt = ModelUtils.tripleToStatement(model, t);
if ( stmt != null )
model.add(stmt);
}
}
finally {
this.close();
}
return model;
}
@Override
public Iterator execConstructTriples() {
checkNotClosed();
if ( ! query.isConstructType() )
throw new QueryExecException("Attempt to get a CONSTRUCT model from a "+labelForQuery(query)+" query") ;
// This causes there to be no PROJECT around the pattern.
// That in turn, exposes the initial bindings.
query.setQueryResultStar(true) ;
startQueryIterator() ;
Template template = query.getConstructTemplate() ;
return TemplateLib.calcTriples(template.getTriples(), queryIterator);
}
@Override
public Iterator execConstructQuads() {
checkNotClosed();
if ( ! query.isConstructType() )
throw new QueryExecException("Attempt to get a CONSTRUCT model from a "+labelForQuery(query)+" query") ;
// This causes there to be no PROJECT around the pattern.
// That in turn, exposes the initial bindings.
query.setQueryResultStar(true) ;
startQueryIterator() ;
Template template = query.getConstructTemplate() ;
return TemplateLib.calcQuads(template.getQuads(), queryIterator);
}
@Override
public Dataset execConstructDataset(){
return execConstructDataset(DatasetFactory.create()) ;
}
@Override
public Dataset execConstructDataset(Dataset dataset) {
DatasetGraph dsg = dataset.asDatasetGraph() ;
try {
execConstructQuads().forEachRemaining(dsg::add);
insertPrefixesInto(dataset);
} finally {
this.close();
}
return dataset ;
}
@Override
public Model execDescribe()
{ return execDescribe(GraphFactory.makeJenaDefaultModel()) ; }
@Override
public Model execDescribe(Model model) {
checkNotClosed() ;
if ( ! query.isDescribeType() )
throw new QueryExecException("Attempt to get a DESCRIBE result from a "+labelForQuery(query)+" query") ;
//Was: query.setQueryResultStar(true) ; but why?
query.setResultVars() ;
// If there was no WhereClause, use an empty pattern (one solution, no columns).
if ( query.getQueryPattern() == null )
query.setQueryPattern(new ElementGroup()) ;
Set set = new HashSet<>() ;
//May return null (no query pattern)
ResultSet qRes = execResultSet() ;
// Prefixes for result (after initialization)
insertPrefixesInto(model) ;
if ( qRes != null ) {
for ( ; qRes.hasNext() ; ) {
QuerySolution rb = qRes.nextSolution();
for ( String varName : query.getResultVars() ) {
RDFNode n = rb.get(varName);
set.add(n);
}
}
}
if ( query.getResultURIs() != null ) {
// Any URIs in the DESCRIBE
for ( Node n : query.getResultURIs() ) {
// Need to make dataset available to describe handlers.
RDFNode rNode = ModelUtils.convertGraphNodeToRDFNode(n, dataset.getDefaultModel());
set.add(rNode);
}
}
// Create new handlers for this process.
List dhList = DescribeHandlerRegistry.get().newHandlerList() ;
getContext().put(ARQConstants.sysCurrentDataset, getDataset()) ;
// Notify start of describe phase
for (DescribeHandler dh : dhList)
dh.start(model, getContext()) ;
// Do describe for each resource found.
for ( RDFNode n : set ) {
if ( n instanceof Resource ) {
for ( DescribeHandler dh : dhList ) {
dh.describe((Resource)n);
}
} else {
// Can't describe literals
continue;
}
}
for ( DescribeHandler dh : dhList )
dh.finish();
this.close();
return model;
}
// TODO not memory efficient
@Override
public Iterator execDescribeTriples() {
return ModelUtils.statementsToTriples(execDescribe().listStatements());
}
@Override
public boolean execAsk() {
checkNotClosed();
if ( !query.isAskType() )
throw new QueryExecException("Attempt to have boolean from a " + labelForQuery(query) + " query");
startQueryIterator();
boolean r = queryIterator.hasNext();
this.close();
return r;
}
@Override
public void setTimeout(long timeout, TimeUnit timeUnit) {
// Overall timeout - recorded as (UNSET,N)
long x = asMillis(timeout, timeUnit);
this.timeout1 = TIMEOUT_UNSET;
this.timeout2 = x;
}
@Override
public void setTimeout(long timeout) {
setTimeout(timeout, TimeUnit.MILLISECONDS);
}
@Override
public void setTimeout(long timeout1, TimeUnit timeUnit1, long timeout2, TimeUnit timeUnit2) {
// Two timeouts.
long x1 = asMillis(timeout1, timeUnit1);
long x2 = asMillis(timeout2, timeUnit2);
this.timeout1 = x1;
if ( timeout2 < 0 )
this.timeout2 = TIMEOUT_UNSET;
else
this.timeout2 = x2;
}
@Override
public void setTimeout(long timeout1, long timeout2) {
setTimeout(timeout1, TimeUnit.MILLISECONDS, timeout2, TimeUnit.MILLISECONDS);
}
private static long asMillis(long duration, TimeUnit timeUnit) {
return (duration < 0) ? duration : timeUnit.toMillis(duration);
}
@Override
public long getTimeout1() { return timeout1 ; }
@Override
public long getTimeout2() { return timeout2 ; }
private static boolean isTimeoutSet(long x) {
return x >= 0;
}
class TimeoutCallback implements Runnable {
@Override
public void run() {
synchronized (lockTimeout) {
// Abort query if and only if we are the expected callback.
// If the first row has appeared, and we are removing timeout1
// callback,
// it still may go off so it needs to check here it's still
// wanted.
if ( expectedCallback == this )
QueryExecutionBase.this.abort();
}
}
}
private class QueryIteratorTimer2 extends QueryIteratorWrapper {
public QueryIteratorTimer2(QueryIterator qIter) {
super(qIter);
}
long yieldCount = 0 ;
boolean resetDone = false ;
@Override
protected Binding moveToNextBinding()
{
Binding b = super.moveToNextBinding() ;
yieldCount++ ;
if ( ! resetDone )
{
// Sync on calls of .abort.
// So nearly not needed.
synchronized(lockTimeout)
{
TimeoutCallback callback = new TimeoutCallback() ;
expectedCallback = callback ;
// Lock against calls of .abort() or of timeout1Callback.
// Update/check the volatiles in a careful order.
// This cause timeout1 not to call .abort and hence not set isCancelled
// But if timeout1 went off after moveToNextBinding, before expectedCallback is set,
// then formget the row and cacnel the query.
if ( isCancelled )
// timeout1 went off after the binding was yielded but
// before we got here.
throw new QueryCancelledException() ;
if ( timeout1Alarm != null ) {
alarmClock.cancel(timeout1Alarm) ;
timeout1Alarm = null ;
}
// Now arm the second timeout, if any.
if ( timeout2 > 0 ) {
// Not first timeout - finite second timeout.
timeout2Alarm = alarmClock.add(callback, timeout2) ;
}
resetDone = true ;
}
}
return b ;
}
}
protected void execInit() { }
private ResultSet asResultSet(QueryIterator qIter) {
Model model = null ;
if ( dataset != null )
model = dataset.getDefaultModel() ;
else
model = ModelFactory.createDefaultModel() ;
ResultSetStream rStream = new ResultSetStream(query.getResultVars(), model, qIter) ;
return rStream ;
}
/** Start the query iterator, setting timeouts as needed. */
private void startQueryIterator() {
execInit() ;
if ( queryIterator != null )
Log.warn(this, "Query iterator has already been started") ;
/* Timeouts:
* -1,-1 No timeouts
* N, same as -1,N Overall timeout only. No wrapper needed.
* N,-1 Timeout on first row only. Need to cancel on first row.
* N,M First/overall timeout. Need to reset on first row.
*/
if ( !isTimeoutSet(timeout1) && !isTimeoutSet(timeout2) ) {
// Case -1,-1
queryIterator = getPlan().iterator();
return;
}
if ( !isTimeoutSet(timeout1) && isTimeoutSet(timeout2) ) {
// Single overall timeout.
TimeoutCallback callback = new TimeoutCallback() ;
expectedCallback = callback ;
timeout2Alarm = alarmClock.add(callback, timeout2) ;
// Start the query.
queryIterator = getPlan().iterator() ;
// But don't add resetter.
return ;
}
// Case isTimeoutSet(timeout1)
// Whether timeout2 is set is determined by QueryIteratorTimer2
// Subcase 2: ! isTimeoutSet(timeout2)
// Add timeout to first row.
TimeoutCallback callback = new TimeoutCallback() ;
timeout1Alarm = alarmClock.add(callback, timeout1) ;
expectedCallback = callback ;
// We don't know if getPlan().iterator() does a lot of work or not
// (ideally it shouldn't start executing the query but in some sub-systems
// it might be necessary)
queryIterator = getPlan().iterator() ;
// Add the timeout1 resetter wrapper.
queryIterator = new QueryIteratorTimer2(queryIterator) ;
// Minor optimization - the first call of hasNext() or next() will
// throw QueryCancelledExcetion anyway. This just makes it a bit earlier
// in the case when the timeout (timoeut1) is so short it's gone off already.
if ( isCancelled ) queryIterator.cancel() ;
}
private ResultSet execResultSet() {
startQueryIterator();
return asResultSet(queryIterator);
}
public Plan getPlan() {
if ( plan == null ) {
DatasetGraph dsg = prepareDataset(dataset, query);
Binding inputBinding = null;
if ( initialBinding != null )
inputBinding = BindingUtils.asBinding(initialBinding);
if ( inputBinding == null )
inputBinding = BindingRoot.create();
plan = qeFactory.create(query, dsg, inputBinding, getContext());
}
return plan;
}
private void insertPrefixesInto(Model model) {
try {
if ( dataset != null ) {
// Load the models prefixes first
PrefixMapping m = dataset.getDefaultModel();
model.setNsPrefixes(m);
}
// Then add the queries (just the declared mappings)
// so the query declarations override the data sources.
model.setNsPrefixes(query.getPrefixMapping());
}
catch (Exception ex) {
Log.warn(this, "Exception in insertPrefixes: " + ex.getMessage(), ex);
}
}
private void insertPrefixesInto(Dataset ds) {
insertPrefixesInto(ds.getDefaultModel()) ;
}
static private String labelForQuery(Query q) {
if ( q.isSelectType() ) return "SELECT" ;
if ( q.isConstructType() ) return "CONSTRUCT" ;
if ( q.isDescribeType() ) return "DESCRIBE" ;
if ( q.isAskType() ) return "ASK" ;
return "<>" ;
}
@Override
public Context getContext() { return context ; }
@Override
public Dataset getDataset() { return dataset ; }
@Override
public Query getQuery() { return query ; }
private static DatasetGraph prepareDataset(Dataset dataset, Query query) {
if ( dataset != null )
return dataset.asDatasetGraph();
if ( ! query.hasDatasetDescription() )
//Query.Log.warn(this, "No data for query (no URL, no model)");
throw new QueryExecException("No dataset description for query");
String baseURI = query.getBaseURI() ;
if ( baseURI == null )
baseURI = IRIResolver.chooseBaseURI().toString() ;
DatasetGraph dsg = DatasetUtils.createDatasetGraph(query.getDatasetDescription(), baseURI ) ;
return dsg ;
}
@Override
public void setInitialBinding(QuerySolution startSolution) {
initialBinding = startSolution ;
}
//protected QuerySolution getInputBindings() { return initialBinding ; }
public void setInitialBindings(ResultSet table)
{ throw new UnsupportedOperationException("setInitialBindings(ResultSet)") ; }
}
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