Apache Parquet is capable of effectively storing nested data storage column format.
Parquet file consists of a file header (header), followed by one or more file block (block), and a file trailer (footer) for the end configuration. Header contains only
Parquet files for each file block is responsible for storing a group of lines, blocks row by the column group, and a column block is responsible for storing a data. Each column of data in block units of a page.
Parquet Map reduce
Parquet files into text files
import java.io.IOException;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericRecord;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import parquet.avro.AvroParquetOutputFormat;
import parquet.example.data.Group;
/**
* Convert text files to Parquet files using Parquet's {@code AvroParquetOutputFormat}.
*/
public class TextToParquetWithAvro extends Configured implements Tool {
private static final Schema SCHEMA = new Schema.Parser().parse(
"{\n" +
" \"type\": \"record\",\n" +
" \"name\": \"Line\",\n" +
" \"fields\": [\n" +
" {\"name\": \"offset\", \"type\": \"long\"},\n" +
" {\"name\": \"line\", \"type\": \"string\"}\n" +
" ]\n" +
"}");
public static class TextToParquetMapper
extends Mapper<LongWritable, Text, Void, GenericRecord> {
private GenericRecord record = new GenericData.Record(SCHEMA);
@Override
protected void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
record.put("offset", key.get());
record.put("line", value.toString());
context.write(null, record);
}
}
@Override
public int run(String[] args) throws Exception {
if (args.length != 2) {
System.err.printf("Usage: %s [generic options] <input> <output>\n",
getClass().getSimpleName());
ToolRunner.printGenericCommandUsage(System.err);
return -1;
}
Job job = new Job(getConf(), "Text to Parquet");
job.setJarByClass(getClass());
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.setMapperClass(TextToParquetMapper.class);
job.setNumReduceTasks(0);
job.setOutputFormatClass(AvroParquetOutputFormat.class);
AvroParquetOutputFormat.setSchema(job, SCHEMA);
job.setOutputKeyClass(Void.class);
job.setOutputValueClass(Group.class);
return job.waitForCompletion(true) ? 0 : 1;
}
public static void main(String[] args) throws Exception {
int exitCode = ToolRunner.run(new TextToParquetWithAvro(), args);
System.exit(exitCode);
}
}