/**
* Copyright 2013 Cloudera Inc.
*
* Licensed 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 com.cloudera.cdk.examples.data;
import com.cloudera.cdk.data.Dataset;
import com.cloudera.cdk.data.DatasetReader;
import com.cloudera.cdk.data.DatasetRepositories;
import com.cloudera.cdk.data.DatasetRepository;
import com.cloudera.cdk.data.PartitionKey;
import com.cloudera.cdk.data.PartitionStrategy;
import org.apache.avro.generic.GenericRecord;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
/**
* Read one partition of user objects from the users dataset using Avro generic records.
*/
public class ReadUserDatasetGenericOnePartition extends Configured implements Tool {
@Override
public int run(String[] args) throws Exception {
// Construct a filesystem dataset repository rooted at /tmp/data
DatasetRepository repo = DatasetRepositories.open("repo:hdfs:/tmp/data");
// Load the users dataset
Dataset<GenericRecord> users = repo.load("users");
// Get the partition strategy and use it to construct a partition key for
// hash(username)=0
PartitionStrategy partitionStrategy = users.getDescriptor().getPartitionStrategy();
PartitionKey partitionKey = partitionStrategy.partitionKey(0);
// Get the dataset partition for the partition key
Dataset<GenericRecord> partition = users.getPartition(partitionKey, false);
// Get a reader for the partition and read all the users
DatasetReader<GenericRecord> reader = partition.newReader();
try {
reader.open();
for (GenericRecord user : reader) {
System.out.println(user);
}
} finally {
reader.close();
}
return 0;
}
public static void main(String... args) throws Exception {
int rc = ToolRunner.run(new ReadUserDatasetGenericOnePartition(), args);
System.exit(rc);
}
}