| /* |
| * 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 com.hp.hpl.jena.sparql.algebra.optimize; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| import com.hp.hpl.jena.sparql.algebra.Op; |
| import com.hp.hpl.jena.sparql.algebra.TransformCopy; |
| import com.hp.hpl.jena.sparql.algebra.op.OpAssign; |
| import com.hp.hpl.jena.sparql.algebra.op.OpExtend; |
| import com.hp.hpl.jena.sparql.algebra.op.OpExtendAssign; |
| import com.hp.hpl.jena.sparql.algebra.op.OpProject; |
| import com.hp.hpl.jena.sparql.core.Var; |
| import com.hp.hpl.jena.sparql.core.VarExprList; |
| import com.hp.hpl.jena.sparql.expr.Expr; |
| |
| /** |
| * A transform capable of removing assignments from the algebra tree |
| * |
| */ |
| public class TransformRemoveAssignment extends TransformCopy { |
| |
| private Var var; |
| private Expr expr; |
| private boolean topmostOnly = true; |
| private boolean aboveExtend = false; |
| |
| public TransformRemoveAssignment(Var var, Expr expr, boolean topmostOnly) { |
| this.var = var; |
| this.expr = expr; |
| this.topmostOnly = topmostOnly; |
| } |
| |
| public TransformRemoveAssignment(Var var, Expr expr) { |
| this(var, expr, true); |
| } |
| |
| @Override |
| public Op transform(OpAssign opAssign, Op subOp) { |
| VarExprList assignments = processAssignments(opAssign); |
| if (assignments == null) |
| return super.transform(opAssign, subOp); |
| |
| // Rewrite appropriately |
| if (this.topmostOnly) { |
| // If topmost only ignore any transformations lower down the tree |
| // hence call getSubOp() rather than using the provided subOp |
| if (assignments.size() > 0) { |
| return OpAssign.assign(opAssign.getSubOp(), assignments); |
| } else { |
| return opAssign.getSubOp(); |
| } |
| } else { |
| // Otherwise preserve any transformations from lower down the tree |
| if (assignments.size() > 0) { |
| return OpAssign.assign(subOp, assignments); |
| } else { |
| return subOp; |
| } |
| } |
| } |
| |
| private VarExprList processAssignments(OpExtendAssign opAssign) { |
| VarExprList orig = opAssign.getVarExprList(); |
| if (!orig.contains(this.var)) |
| return null; |
| if (!orig.getExpr(this.var).equals(this.expr)) |
| return null; |
| |
| VarExprList modified = new VarExprList(); |
| for (Var v : orig.getVars()) { |
| if (!v.equals(this.var)) { |
| modified.add(v, orig.getExpr(v)); |
| } |
| } |
| if (modified.size() > 0 && modified.size() == orig.size()) |
| return null; |
| |
| return modified; |
| } |
| |
| @Override |
| public Op transform(OpExtend opExtend, Op subOp) { |
| VarExprList assignments = processAssignments(opExtend); |
| if (assignments == null) |
| return super.transform(opExtend, subOp); |
| |
| this.aboveExtend = true; |
| |
| // Rewrite appropriately |
| if (this.topmostOnly) { |
| // If topmost only ignore any transformations lower down the tree |
| // hence call getSubOp() rather than using the provided subOp |
| if (assignments.size() > 0) { |
| return OpExtend.create(opExtend.getSubOp(), assignments); |
| } else { |
| return opExtend.getSubOp(); |
| } |
| } else { |
| // Otherwise preserve any transformations from lower down the tree |
| if (assignments.size() > 0) { |
| return OpExtend.create(subOp, assignments); |
| } else { |
| return subOp; |
| } |
| } |
| |
| } |
| |
| public Op transform(OpProject opProject, Op subOp) { |
| if (!opProject.getVars().contains(this.var)) |
| return super.transform(opProject, subOp); |
| |
| List<Var> newVars = new ArrayList<Var>(opProject.getVars()); |
| newVars.remove(this.var); |
| if (this.topmostOnly) { |
| if (this.aboveExtend) { |
| return new OpProject(subOp, newVars); |
| } else { |
| return opProject; |
| } |
| } else { |
| return new OpProject(subOp, newVars); |
| } |
| } |
| } |