apache pig - Merging multiple files into one within Hadoop

Question

I get multiple small files into my input directory which I want to merge into a single file without using the local file system or writing mapreds. Is there a way I could do it using hadoof fs commands or Pig?

Thanks!

Answer 1

In order to keep everything on the grid use hadoop streaming with a single reducer and cat as the mapper and reducer (basically a noop) - add compression using MR flags.

hadoop jar 
    $HADOOP_PREFIX/share/hadoop/tools/lib/hadoop-streaming.jar <br>
    -Dmapred.reduce.tasks=1 
    -Dmapred.job.queue.name=$QUEUE 
    -input "$INPUT" 
    -output "$OUTPUT" 
    -mapper cat 
    -reducer cat

If you want compression add
-Dmapred.output.compress=true -Dmapred.output.compression.codec=org.apache.hadoop.io.compress.GzipCodec