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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 org.apache.jena.atlas.lib.Closeable ;
import org.apache.jena.atlas.logging.Log ;
import org.apache.jena.query.Query ;
import org.apache.jena.query.QueryExecException;
import org.apache.jena.riot.system.IRIResolver;
import org.apache.jena.sparql.ARQConstants ;
import org.apache.jena.sparql.algebra.Algebra ;
import org.apache.jena.sparql.algebra.Op ;
import org.apache.jena.sparql.core.DatasetDescription;
import org.apache.jena.sparql.core.DatasetGraph ;
import org.apache.jena.sparql.core.DynamicDatasets;
import org.apache.jena.sparql.core.Substitute ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.binding.BindingRoot ;
import org.apache.jena.sparql.mgt.Explain ;
import org.apache.jena.sparql.mgt.QueryEngineInfo ;
import org.apache.jena.sparql.util.Context ;
import org.apache.jena.sparql.util.DatasetUtils;
/** Main part of a QueryEngine - something that takes responsibility for a complete query execution */
public abstract class QueryEngineBase implements OpEval, Closeable
{
public final static QueryEngineInfo queryEngineInfo = new QueryEngineInfo() ;
// See also ExecutionContext.getDataset()
protected final DatasetGraph originalDataset ;
protected DatasetGraph dataset = null ;
protected Context context ;
private Binding startBinding ;
private Query query = null ;
private Op queryOp = null ;
private Plan plan = null ;
protected QueryEngineBase(Query query, DatasetGraph dsg, Binding input, Context cxt) {
this(dsg, input, cxt) ;
this.query = query ;
query.setResultVars() ;
// Unoptimized so far.
setOp(createOp(query)) ;
dataset = prepareDataset(dsg, query);
}
private DatasetGraph prepareDataset(DatasetGraph originalDataset, Query query) {
DatasetDescription dsDesc = DatasetDescription.create(query, context) ;
DatasetGraph dsg = originalDataset;
if ( dsg != null ) {
if ( dsDesc != null ) {
if ( query.hasDatasetDescription() )
dsg = dynamicDataset(dsDesc, dsg, false);
}
return dsg;
}
// No DatasetGraph
if ( ! query.hasDatasetDescription() )
throw new QueryExecException("No dataset and no dataset description for query");
// DatasetDescription : Build it.
String baseURI = query.getBaseURI() ;
if ( baseURI == null )
baseURI = IRIResolver.chooseBaseURI().toString() ;
dsg = DatasetUtils.createDatasetGraph(dsDesc, baseURI ) ;
return dsg ;
}
protected QueryEngineBase(Op op, DatasetGraph dataset, Binding input, Context cxt) {
this(dataset, input, cxt) ;
// Ensure context setup - usually done in QueryExecutionBase
// so it can be changed after initialization.
if ( context == null )
context = Context.setupContextForDataset(context, dataset) ;
Context.setCurrentDateTime(context) ;
this.query = null ;
setOp(op) ;
}
private QueryEngineBase(DatasetGraph dataset, Binding input, Context context) {
this.context = context ;
this.originalDataset = dataset ;
this.dataset = dataset ;
if ( input == null ) {
Log.warn(this, "Null initial input") ;
input = BindingRoot.create() ;
}
this.startBinding = input ;
}
public Plan getPlan()
{
if ( plan == null )
plan = createPlan() ;
return plan ;
}
protected Plan createPlan()
{
// Decide the algebra to actually execute.
Op op = queryOp ;
if ( ! startBinding.isEmpty() ) {
op = Substitute.substitute(op, startBinding) ;
context.put(ARQConstants.sysCurrentAlgebra, op) ;
// Don't reset the startBinding because it also is
// needed in the output.
}
op = modifyOp(op) ;
QueryIterator queryIterator = null ;
if ( dataset != null )
// Null means setting up but not executing a query.
queryIterator = evaluate(op, dataset, startBinding, context) ;
else
// Bypass management interface
queryIterator = evaluateNoMgt(op, dataset, startBinding, context) ;
// This could be an automagic iterator to catch close.
return new PlanOp(getOp(), this, queryIterator) ;
}
protected Op modifyOp(Op op)
{ return op ; }
protected Op createOp(Query query)
{
Op op = Algebra.compile(query) ;
return op ;
}
/** Calculate a dataset based on FROM and FROM NAMED in the query */
protected DatasetGraph dynamicDataset(DatasetDescription dsDesc, DatasetGraph dataset, boolean unionDftGraph) {
return DynamicDatasets.dynamicDataset(dsDesc, dataset, unionDftGraph) ;
}
/**
* Return whether the dataset to execute against is the original one, or a
* DatasetDescription modified one (including one for provided then the dataset was
* null).
*/
protected boolean isDynamicDataset() {
return originalDataset != dataset;
}
// Record the query operation as it goes pass and call the actual worker
@Override
final
public QueryIterator evaluate(Op op, DatasetGraph dsg, Binding binding, Context context)
{
if ( query != null )
Explain.explain("QUERY", query, context) ;
Explain.explain("ALGEBRA", op, context) ;
queryEngineInfo.incQueryCount() ;
queryEngineInfo.setLastQueryExecAt() ;
//queryEngineInfo.setLastQueryExecTime(-1) ;
queryEngineInfo.setLastQueryString((Query)context.get(ARQConstants.sysCurrentQuery)) ;
queryEngineInfo.setLastOp(op) ;
return eval(op, dsg, binding, context) ;
}
private QueryIterator evaluateNoMgt(Op op, DatasetGraph dsg, Binding binding, Context context)
{
return eval(op, dsg, binding, context) ;
}
abstract protected
QueryIterator eval(Op op, DatasetGraph dsg, Binding binding, Context context) ;
/** Algebra expression (including any optimization) */
public Op getOp() { return queryOp ; }
protected Binding getStartBinding() { return startBinding ; }
@Override
public void close()
{ }
protected void setOp(Op op)
{
queryOp = op ;
context.put(ARQConstants.sysCurrentAlgebra, op) ;
}
}