MapReduce读写ORC文件

灰太狼 2022-05-22 05:37 262阅读 0赞

**MapReduce读写ORC文件**

ORC的全称是Optimized Row Columnar。ORC文件格式是hadoop生态圈中的一种列式存储格式，最早来自于Apache Hive， 有着非常高的压缩比和读取效率，成为Hive中常用的一种文件格式。

**1、读ORC文件**

OrcFileReadMapper.java
    ---------------------------------------
    import org.apache.hadoop.io.NullWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Mapper;
    import org.apache.orc.mapred.OrcStruct;
    
    import java.io.IOException;
    
    /**
    * @author lyf
    * @since 2018/06/16
    */
    public class OrcFileReadMapper extends Mapper<NullWritable, OrcStruct, Text, NullWritable> {
    
        private Text outputKey = new Text();
    
        @Override
        protected void map(NullWritable key, OrcStruct value, Context context) throws IOException, InterruptedException {
            StringBuffer sb= new StringBuffer();
    
            sb.append(value.getFieldValue(0));      //通过下标索引获取数据
            sb.append(value.getFieldValue(1));
            sb.append(value.getFieldValue(2));
            sb.append(value.getFieldValue("age"));      //也可以通过字段名获取数据
    
            // 打印输出获取到的数据
            System.out.println(sb.toString());
            outputKey = new Text(sb.toString());
    
            context.write(outputKey, NullWritable.get());
        }
    }

OrcFileReadJob.java
    ------------------------------
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.conf.Configured;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.NullWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Job;
    import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
    import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
    import org.apache.hadoop.util.Tool;
    import org.apache.hadoop.util.ToolRunner;
    import org.apache.orc.mapreduce.OrcInputFormat;
    
    import java.io.IOException;
    
    /**
    * @author lyf
    * @since 2018/06/16
    */
    public class OrcFileReadJob extends Configured implements Tool {
    
        @Override
        public int run(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
    
            Configuration conf = getConf();
    
            String input = "input";
            String output = "output";
    
            Job job = Job.getInstance(conf);
    
            job.setJarByClass(OrcFileReadJob.class);
            job.setMapperClass(OrcFileReadMapper.class);
    
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(NullWritable.class);
            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(NullWritable.class);
    
            job.setInputFormatClass(OrcInputFormat.class);      //设置输入格式为Orc格式
            job.setOutputFormatClass(TextOutputFormat.class);       //输出格式为文本格式
    
            OrcInputFormat.addInputPath(job, new Path(input));      //以Orc的方式加载输入路径
            FileOutputFormat.setOutputPath(job, new Path(output));
    
            boolean rt = job.waitForCompletion(true);
            return rt?0:1;
        }
    
        public static void main(String[] args) throws Exception {
            Configuration conf = new Configuration();
            int retnum = ToolRunner.run(conf,new OrcFileReadJob(),args);
        }
    }

**2、写ORC文件**

OrcFileWriteMapper.java
    ----------------------------------------------------------------
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.LongWritable;
    import org.apache.hadoop.io.NullWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Mapper;
    import org.apache.hadoop.mapreduce.lib.input.FileSplit;
    
    import java.io.IOException;
    
    /**
    * @author lyf
    * @since 2018/06/16
    */
    public class OrcFileWriteMapper extends Mapper<LongWritable,Text,Text,IntWritable> {
    
        Text outputKey = new Text();
        IntWritable outputValue = new IntWritable(1);
    
    /*    @Override
        protected void setup(Context context) {
            String filePath = ((FileSplit) context.getInputSplit()).getPath().toString();
            System.out.println("filePath:" + filePath);
        }*/
    
        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            outputKey = value;
            context.write(outputKey,outputValue);
        }
    }

OrcFileWriteReducer.java
    ----------------------------------------------------------------------
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.LongWritable;
    import org.apache.hadoop.io.NullWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Reducer;
    import org.apache.orc.TypeDescription;
    import org.apache.orc.mapred.OrcStruct;
    
    import java.io.IOException;
    
    /**
    * @author lyf
    * @since 2018/06/16
    */
    public class OrcFileWriteReducer extends Reducer<Text,IntWritable,NullWritable,OrcStruct> {
    
      //要创建的ORC文件中的字段类型
        private TypeDescription schema = TypeDescription.fromString(
                "struct<id:string," +
                        "name:string," +
                        "sex:string," +
                        "age:int>"
        );
    
        private OrcStruct pair = (OrcStruct)OrcStruct.createValue(schema);
    
        @Override
        protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
            String line = key.toString();
            String[] lineSplit = line.trim().split(" ");
    
            pair.setFieldValue(0,new Text(lineSplit[0]));
            pair.setFieldValue(1,new LongWritable(Long.parseLong(lineSplit[1])));
            pair.setFieldValue(2,new Text(lineSplit[2]));
            pair.setFieldValue(3,new Text(lineSplit[3]));
            pair.setFieldValue(4,new Text(lineSplit[4]));
    
            context.write(NullWritable.get(),pair);
        }
    }

OrcFileWriteJob.java
    ------------------------------------------------------------------------------
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.conf.Configured;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.NullWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Job;
    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 org.apache.orc.mapred.OrcStruct;
    import org.apache.orc.mapreduce.OrcOutputFormat;
    
    import java.io.IOException;
    
    /**
    * @author lyf
    * @since 2018/06/16
    */
    public class OrcFileWriteJob extends Configured implements Tool {
        @Override
        public int run(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
            Configuration conf = getConf();
    
            conf.set("orc.mapred.output.schema","struct<id:string,name:string,sex:string,age:int>");
            String input = "input";
            String output = "output";
    
            Job job = Job.getInstance(conf);
    
            job.setJarByClass(OrcFileWriteJob.class);
            job.setMapperClass(OrcFileWriteMapper.class);
            job.setReducerClass(OrcFileWriteReducer.class);
    
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(IntWritable.class);
            job.setOutputKeyClass(NullWritable.class);
            job.setOutputValueClass(OrcStruct.class);
    
            job.setOutputFormatClass(OrcOutputFormat.class);
            FileInputFormat.addInputPath(job,new Path(input));
            FileOutputFormat.setOutputPath(job,new Path(output));
    
            boolean rt = job.waitForCompletion(true);
            return rt?0:1;
        }
    
        public static void main(String[] args) throws Exception {
            Configuration conf = new Configuration();
            int retnum = ToolRunner.run(conf,new OrcFileWriteJob(),args);
        }
    }