| /** |
| * 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.join; |
| |
| import org.apache.jena.atlas.logging.Log ; |
| 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.QueryIterNullIterator ; |
| import org.apache.jena.sparql.expr.ExprList ; |
| |
| /** |
| * Hash left join. |
| * |
| * This code materializes the right hand side into a probe table then hash joins |
| * from the left. |
| * |
| * See {@link QueryIterHashLeftJoin_Left} for one that uses the right hand side |
| * to make the probe table. |
| */ |
| |
| //* This code materializes the left into a probe table |
| //* then hash joins from the right. |
| |
| public class QueryIterHashLeftJoin_Right extends AbstractIterHashJoin { |
| // Left join conditions |
| private final ExprList conditions; |
| |
| /** |
| * Create a hashjoin QueryIterator. |
| * @param joinKey Join key - if null, one is guessed by snooping the input QueryIterators |
| * @param left |
| * @param right |
| * @param conditions |
| * @param execCxt |
| * @return QueryIterator |
| */ |
| public static QueryIterator create(JoinKey joinKey, QueryIterator left, QueryIterator right, ExprList conditions, ExecutionContext execCxt) { |
| // Easy cases. |
| if ( ! left.hasNext() ) { |
| left.close() ; |
| right.close() ; |
| return QueryIterNullIterator.create(execCxt) ; |
| } |
| if ( ! right.hasNext() ) { |
| right.close() ; |
| return left ; |
| } |
| |
| if ( joinKey != null && joinKey.length() > 1 ) |
| Log.warn(QueryIterHashLeftJoin_Right.class, "Multivariable join key") ; |
| |
| return new QueryIterHashLeftJoin_Right(joinKey, left, right, conditions, execCxt) ; |
| } |
| |
| /** |
| * Create a hashjoin QueryIterator. |
| * @param left |
| * @param right |
| * @param execCxt |
| * @return QueryIterator |
| */ |
| public static QueryIterator create(QueryIterator left, QueryIterator right, ExprList conditions, ExecutionContext execCxt) { |
| return create(null, left, right, conditions, execCxt) ; |
| } |
| |
| private QueryIterHashLeftJoin_Right(JoinKey joinKey, QueryIterator left, QueryIterator right, ExprList conditions, ExecutionContext execCxt) { |
| // NB Right. Left |
| super(joinKey, right, left, execCxt) ; |
| this.conditions = conditions ; |
| } |
| |
| @Override |
| protected Binding yieldOneResult(Binding rowCurrentProbe, Binding rowStream, Binding rowResult) { |
| if ( conditions != null && ! conditions.isSatisfied(rowResult, getExecContext()) ) |
| return null ; |
| return rowResult ; |
| } |
| |
| @Override |
| protected Binding noYieldedRows(Binding rowCurrentProbe) { |
| return rowCurrentProbe; |
| } |
| |
| @Override |
| protected QueryIterator joinFinished() { |
| return null ; |
| } |
| } |
| |
| |