| /* |
| * 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.algebra; |
| |
| import java.util.ArrayDeque ; |
| import java.util.Deque ; |
| |
| import org.apache.jena.graph.Node ; |
| import org.apache.jena.sparql.ARQInternalErrorException ; |
| import org.apache.jena.sparql.algebra.op.OpBGP ; |
| import org.apache.jena.sparql.algebra.op.OpDistinct ; |
| import org.apache.jena.sparql.algebra.op.OpGraph ; |
| import org.apache.jena.sparql.algebra.op.OpQuadPattern ; |
| import org.apache.jena.sparql.core.Quad ; |
| import org.apache.jena.sparql.core.Var ; |
| |
| /** Convert query in algebra form so that the default graph of the query is the union of named graphs */ |
| public class TransformUnionQuery extends TransformCopy |
| { |
| public static Op transform(Op op) |
| { |
| TransformUnionQuery t = new TransformUnionQuery() ; |
| Op op2 = Transformer.transform(t, op, new Pusher(t.currentGraph), new Popper(t.currentGraph)) ; |
| return op2 ; |
| } |
| |
| // ** SEE AlgebraQuad : Pusher and Popper :share. |
| Deque<Node> currentGraph = new ArrayDeque<>() ; |
| |
| public TransformUnionQuery() |
| { |
| currentGraph.push(Quad.defaultGraphNodeGenerated) ; |
| } |
| |
| @Override |
| public Op transform(OpQuadPattern quadPattern) |
| { |
| if ( quadPattern.isDefaultGraph() || quadPattern.isUnionGraph() ) |
| { |
| OpBGP opBGP = new OpBGP(quadPattern.getBasicPattern()) ; |
| return union(opBGP) ; |
| } |
| |
| // Leave alone. |
| // if ( quadPattern.isExplicitDefaultGraph() ) {} |
| return super.transform(quadPattern) ; |
| } |
| |
| @Override |
| public Op transform(OpBGP opBGP) |
| { |
| Node current = currentGraph.peek(); |
| if ( current == Quad.defaultGraphNodeGenerated || current == Quad.unionGraph ) |
| return union(opBGP) ; |
| // // Turn into a quad pattern. |
| // // Not perfect - see AlgebraQuad |
| // return new OpQuadPattern(currentGraph.peek(), opBGP.getPattern()) ; |
| // BGP over a named graph. |
| // Leave as-is. |
| return super.transform(opBGP) ; |
| } |
| |
| private Op union(OpBGP opBGP) |
| { |
| // By using the unbinding Var.ANON, the distinct works. |
| // Else, we get duplicates from projection out of the graph var. |
| Var v = Var.ANON ; //varAlloc.allocVar() ; |
| Op op = new OpGraph(v, opBGP) ; |
| op = OpDistinct.create(op) ; |
| return op ; |
| } |
| |
| @Override |
| public Op transform(OpGraph opGraph, Op x) |
| { |
| // Remove any Quad.unionGraph - OpBGPs will be rewritten. |
| return super.transform(opGraph, x) ; |
| } |
| |
| static class Pusher extends OpVisitorBase |
| { |
| private Deque<Node> stack ; |
| Pusher(Deque<Node> stack) { this.stack = stack ; } |
| @Override |
| public void visit(OpGraph opGraph) |
| { |
| stack.push(opGraph.getNode()) ; |
| } |
| } |
| |
| static class Popper extends OpVisitorBase |
| { |
| private Deque<Node> stack ; |
| Popper(Deque<Node> stack) { this.stack = stack ; } |
| @Override |
| public void visit(OpGraph opGraph) |
| { |
| Node n = stack.pop() ; |
| if ( ! opGraph.getNode().equals(n)) |
| throw new ARQInternalErrorException() ; |
| } |
| } |
| } |