Take the output of “select” in hive as the input of Hadoop jar input file

Question

I am experimenting with a machine learning package called vowpal wabbit. To run vowpal wabbit on our hadoop cluster, it recommends to do:

hadoop jar /usr/lib/hadoop-0.20-mapreduce/contrib/streaming/hadoop-streaming-2.0.0-mr1-cdh4.3.0.jar \
    -Dmapred.job.name="vw allreduce $in_directory" \
    -Dmapred.map.tasks.speculative.execution=true \
    -Dmapred.reduce.tasks=0 \
    -Dmapred.child.java.opts="-Xmx100m" \
    -Dmapred.task.timeout=600000000 \
    -Dmapred.job.map.memory.mb=1000 \
    -input <in_directory> \
    -output <out_directory> \
    -file /home/produser/vowpal_wabbit/vowpalwabbit/vw \
    -file /usr/lib64/libboost_program_options.so.5 \
    -file /lib64/libz.so.1 \
    -file /home/produser/vowpal_wabbit/cluster/runvw-yarn.sh \
    -mapper /home/produser/vowpal_wabbit/cluster/runvw-yarn.sh \
    -reducer NONE

where runvw-yarn.sh, as a mapper, will call vowpal wabbit's command on each machine with the piece of data that's stored on it

I have to reformat the data before I pass it in. I tried to use hive query to select the data from the grid, reformat it and then pass it to the "hadoop jar" command. But I don't want to store the reformated data on our cluster to waste the space. So I don't know what to put after the "-input" option in the "hadoop jar" command.

So my question is, is there a way to put something like "stdin" after the "-input" command? And also where should I put that "hadoop jar" command in my hive query after I select the data?

PS I found "hive --service jar" and it looks similar like hadoop jar, is this helpful here?

Thank you! I just started to learn hadoop and hive a couple of weeks ago, so if you have a better design or solution, feel free to let me know. I can rewrite every thing.

Answer 1

It seems that you are gonna run two rounds of Mapreduce: 1st is a Hive query and 2nd is MapReduce stream. As far as I am concerned, to use multi-round Mapreduce jobs, we always need to write/read to/from hdfs between the rounds. That's why MapReduce is always called batch operation.

So, the answer to your question is NO.