/*
* 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.logical.relational;
import java.util.List;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.newplan.Operator;
import org.apache.pig.newplan.OperatorPlan;
import org.apache.pig.newplan.PlanVisitor;
/**
* We can <b>optionally</b> cache intermediate relations into some caching service.
* The default implementation can be a simple no-op.
*/
public class LOCache extends LogicalRelationalOperator {
public LOCache(OperatorPlan plan) {
super("LOCache", plan);
}
@Override
public LogicalSchema getSchema() throws FrontendException {
if (schema == null) {
schema = getPredecessor().getSchema();
}
return schema;
}
@Override
public void accept(PlanVisitor v) throws FrontendException {
if (!(v instanceof LogicalRelationalNodesVisitor)) {
throw new FrontendException("Expected LogicalPlanVisitor", 2223);
}
((LogicalRelationalNodesVisitor)v).visit(this);
}
@Override
public boolean isEqual(Operator operator) throws FrontendException {
return operator instanceof LOCache &&
((LOCache) operator).getPredecessor().isEqual(getPredecessor());
}
public LogicalRelationalOperator getPredecessor() throws FrontendException {
List<Operator> preds = plan.getPredecessors(this);
if (preds != null && preds.size() == 1) {
return (LogicalRelationalOperator) preds.get(0);
} else {
throw new FrontendException("LOCache expects exactly 1 predecessor. Saw " + preds.size());
}
}
}