/*
* 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.backend.datastorage.DataStorage;
/**
* Produces independent slices of data from a given location to be processed in
* parallel by Pig.
* <p>
* If a class implementing this interface is given as the LoadFunc in a Pig
* script, it will be used to make slices for that load statement.
*/
public interface Slicer {
/**
* Checks that <code>location</code> is parsable by this Slicer, and that
* if the DataStorage is used by the Slicer, it's readable from there. If it
* isn't, an IOException with a message explaining why will be thrown.
* <p>
* This does not ensure that all the data in <code>location</code> is
* valid. It's a preflight check that there's some chance of the Slicer
* working before actual Slices are created and sent off for processing.
*/
void validate(DataStorage store, String location) throws IOException;
/**
* Creates slices of data from <code>store</code> at <code>location</code>.
*
* @return the Slices to be serialized and sent out to nodes for processing.
*/
Slice[] slice(DataStorage store, String location) throws IOException;
}