| package org.apache.rya.rdftriplestore.evaluation; |
| |
| /* |
| * 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. |
| */ |
| |
| |
| |
| import org.openrdf.query.algebra.Join; |
| import org.openrdf.query.algebra.StatementPattern; |
| import org.openrdf.query.algebra.TupleExpr; |
| import org.openrdf.query.algebra.helpers.QueryModelVisitorBase; |
| |
| /** |
| * Class ReorderJoinVisitor |
| * Date: Apr 11, 2011 |
| * Time: 10:16:15 PM |
| */ |
| public class ReorderJoinVisitor extends QueryModelVisitorBase<Exception> { |
| @Override |
| public void meet(final Join node) throws Exception { |
| super.meet(node); |
| |
| final TupleExpr leftArg = node.getLeftArg(); |
| final TupleExpr rightArg = node.getRightArg(); |
| |
| /** |
| * if join(stmtPattern1, join(stmtPattern2, anything) |
| * Should be |
| * join(join(stmtPattern1, stmtPattern2), anything) |
| */ |
| if (leftArg instanceof StatementPattern && rightArg instanceof Join) { |
| final Join rightJoin = (Join) rightArg; |
| //find the stmtPattern in the right side |
| final TupleExpr right_LeftArg = rightJoin.getLeftArg(); |
| final TupleExpr right_rightArg = rightJoin.getRightArg(); |
| if (right_LeftArg instanceof StatementPattern || right_rightArg instanceof StatementPattern) { |
| StatementPattern stmtPattern = null; |
| TupleExpr anything = null; |
| if (right_LeftArg instanceof StatementPattern) { |
| stmtPattern = (StatementPattern) right_LeftArg; |
| anything = right_rightArg; |
| } else { |
| stmtPattern = (StatementPattern) right_rightArg; |
| anything = right_LeftArg; |
| } |
| |
| final Join inner = new Join(leftArg, stmtPattern); |
| final Join outer = new Join(inner, anything); |
| node.replaceWith(outer); |
| } |
| } |
| |
| } |
| } |