/*
* 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.pig.newplan.optimizer;
import org.apache.pig.classification.InterfaceAudience;
import org.apache.pig.classification.InterfaceStability;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.newplan.OperatorPlan;
/**
* An interface to describe listeners that are notified when a plan is
* modified. The purpose of these listeners is to make modifications to
* annotations on the plan after the plan is modified. For example, if there
* is a plan that has ... -> Join -> Filter -> ... which is transformed
* by pushing the filter before the join, then the input schema of the filter
* will mostly likely change. A schema listener can be used to make these
* changes.
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public interface PlanTransformListener {
/**
* Notification that a plan has been transformed. The listener is free in
* this method to make changes to the annotations on the plan now that it
* has been transformed.
* @param fp the full plan that has been transformed
* @param tp a plan containing only the operators that have been transformed
* @throws FrontendException
*/
public void transformed(OperatorPlan fp, OperatorPlan tp) throws FrontendException;
}