    001/*
    002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
    003 *
    004 * Project and contact information: http://www.cascading.org/
    005 *
    006 * This file is part of the Cascading project.
    007 *
    008 * Licensed under the Apache License, Version 2.0 (the "License");
    009 * you may not use this file except in compliance with the License.
    010 * You may obtain a copy of the License at
    011 *
    012 *     http://www.apache.org/licenses/LICENSE-2.0
    013 *
    014 * Unless required by applicable law or agreed to in writing, software
    015 * distributed under the License is distributed on an "AS IS" BASIS,
    016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017 * See the License for the specific language governing permissions and
    018 * limitations under the License.
    019 */
    020
    021package cascading.flow.hadoop.planner.rule.scopeexpression;
    022
    023import java.net.URI;
    024
    025import cascading.flow.FlowElement;
    026import cascading.flow.hadoop.planner.HadoopPlanner;
    027import cascading.flow.planner.PlannerContext;
    028import cascading.flow.planner.Scope;
    029import cascading.flow.planner.graph.ElementGraph;
    030import cascading.flow.planner.iso.expression.ScopeExpression;
    031import cascading.tap.hadoop.Hfs;
    032
    033/**
    034 *
    035 */
    036public class EquivalentTapsScopeExpression extends ScopeExpression
    037  {
    038  @Override
    039  public boolean applies( PlannerContext plannerContext, ElementGraph elementGraph, Scope scope )
    040    {
    041    FlowElement edgeSource = elementGraph.getEdgeSource( scope );
    042    FlowElement edgeTarget = elementGraph.getEdgeTarget( scope );
    043
    044    if( !( edgeSource instanceof Hfs ) || !( edgeTarget instanceof Hfs ) )
    045      throw new IllegalStateException( "non Hfs Taps matched" );
    046
    047    Hfs predecessor = (Hfs) edgeSource;
    048    Hfs successor = (Hfs) edgeTarget;
    049
    050    // does this scheme source what it sinks
    051    if( !successor.getScheme().isSymmetrical() )
    052      return false;
    053
    054    HadoopPlanner flowPlanner = (HadoopPlanner) plannerContext.getFlowPlanner();
    055
    056    URI tempURIScheme = flowPlanner.getDefaultURIScheme( predecessor ); // temp uses default fs
    057    URI successorURIScheme = flowPlanner.getURIScheme( successor );
    058
    059    if( !tempURIScheme.equals( successorURIScheme ) )
    060      return false;
    061
    062    // safe, both are symmetrical
    063    // should be called after fields are resolved
    064    if( !predecessor.getSourceFields().equals( successor.getSourceFields() ) )
    065      return true;
    066
    067    return true;
    068    }
    069  }