org.apache.pig.StreamToPig Maven / Gradle / Ivy
/*
* 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;
import java.io.IOException;
import org.apache.pig.classification.InterfaceAudience;
import org.apache.pig.classification.InterfaceStability;
import org.apache.pig.data.Tuple;
/**
* The interface is used for the custom mapping of a byte array, received from
* the stdout of the streaming process, to a {@link Tuple}.
*
* This interface, together with {@link PigToStream}, is designed to provide
* a common protocol for data exchange between Pig runtime and streaming
* executables.
*
* The method getLoadCaster is called by Pig to convert the
* fields in the byte array to typed fields of the Tuple based on a given
* schema.
*
* Typically, user implements this interface for a particular type of
* stream command and specifies the implementation class in the Pig DEFINE
* statement.
* @since Pig 0.7
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public interface StreamToPig {
/**
* Given a byte array from a streaming executable, produce a tuple.
* @param bytes to deserialize.
* @return Data as a Pig Tuple.
*/
public Tuple deserialize(byte[] bytes) throws IOException;
/**
* This will be called on the front end during planning and not on the back
* end during execution.
*
* @return the {@link LoadCaster} associated with this object, or null if
* there is no such LoadCaster.
* @throws IOException if there is an exception during LoadCaster
*/
public LoadCaster getLoadCaster() throws IOException;
}