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* 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.main;
import org.apache.jena.atlas.lib.Lib ;
import org.apache.jena.atlas.logging.Log ;
import org.apache.jena.graph.Graph ;
import org.apache.jena.sparql.core.BasicPattern ;
import org.apache.jena.sparql.core.Substitute ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.iterator.QueryIterBlockTriples ;
import org.apache.jena.sparql.engine.iterator.QueryIterPeek ;
import org.apache.jena.sparql.engine.iterator.QueryIterRoot ;
import org.apache.jena.sparql.engine.optimizer.reorder.ReorderLib ;
import org.apache.jena.sparql.engine.optimizer.reorder.ReorderProc ;
import org.apache.jena.sparql.engine.optimizer.reorder.ReorderTransformation ;
import org.apache.jena.sparql.mgt.Explain ;
/** Generic - always works - StageGenerator */
public class StageGeneratorGeneric implements StageGenerator {
public StageGeneratorGeneric() {}
private static final ReorderTransformation reorderFixed = ReorderLib.fixed() ;
@Override
public QueryIterator execute(BasicPattern pattern, QueryIterator input, ExecutionContext execCxt) {
if ( input == null )
Log.fatal(this, "Null input to " + Lib.classShortName(this.getClass())) ;
Graph graph = execCxt.getActiveGraph() ;
// Choose reorder transformation and execution strategy.
ReorderTransformation reorder = reorderFixed ;
StageGenerator executor = StageBuilder.executeInline ;
return execute(pattern, reorder, executor, input, execCxt) ;
}
protected QueryIterator execute(BasicPattern pattern, ReorderTransformation reorder, StageGenerator execution,
QueryIterator input, ExecutionContext execCxt)
{
Explain.explain(pattern, execCxt.getContext()) ;
if ( ! input.hasNext() )
return input ;
if ( reorder != null && pattern.size() >= 2 ) {
// If pattern size is 0 or one, nothing to do.
BasicPattern bgp2 = pattern ;
// Try to ground the pattern
if ( ! ( input instanceof QueryIterRoot ) ) {
QueryIterPeek peek = QueryIterPeek.create(input, execCxt) ;
Binding b = peek.peek() ;
// And use this one
input = peek ;
bgp2 = Substitute.substitute(pattern, b) ;
// ---- common
ReorderProc reorderProc = reorder.reorderIndexes(bgp2) ;
pattern = reorderProc.reorder(pattern) ;
}
}
Explain.explain("Reorder/generic", pattern, execCxt.getContext()) ;
return QueryIterBlockTriples.create(input, pattern, execCxt) ;
}
}