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From Sanjay Subramanian <Sanjay.Subraman...@wizecommerce.com>
Subject Re: Hive and Lzo Compression
Date Thu, 08 Aug 2013 19:30:49 GMT
Please refer this documentation here
Let me know if u need more clarifications so that we can make this document better and complete

Thanks

sanjay

From: w00t w00t <w00tel@yahoo.de<mailto:w00tel@yahoo.de>>
Reply-To: "user@hive.apache.org<mailto:user@hive.apache.org>" <user@hive.apache.org<mailto:user@hive.apache.org>>,
w00t w00t <w00tel@yahoo.de<mailto:w00tel@yahoo.de>>
Date: Thursday, August 8, 2013 2:02 AM
To: "user@hive.apache.org<mailto:user@hive.apache.org>" <user@hive.apache.org<mailto:user@hive.apache.org>>
Subject: Hive and Lzo Compression


Hello,

I am started to run Hive with Lzo compression on Hortonworks 1.2

I have managed to install/configure Lzo and  hive -e "set io.compression.codecs" shows me
the Lzo Codecs:
io.compression.codecs=
org.apache.hadoop.io.compress.GzipCodec,
org.apache.hadoop.io.compress.DefaultCodec,
com.hadoop.compression.lzo.LzoCodec,
com.hadoop.compression.lzo.LzopCodec,
org.apache.hadoop.io.compress.BZip2Codec

However, I have some questions where I would be happy if you could help me.

(1) CREATE TABLE statement

I read in different postings, that in the CREATE TABLE statement, I have to use the following
STORAGE clause:

CREATE EXTERNAL TABLE txt_table_lzo (
   txt_line STRING
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY '||||'
STORED AS INPUTFORMAT 'com.hadoop.mapred.DeprecatedLzoTextInputFormat' OUTPUTFORMAT 'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
LOCATION '/user/myuser/data/in/lzo_compressed';

It works withouth any problems now to execute SELECT statements on this table with Lzo data.

However I also created a table on the same data without this STORAGE clause:

CREATE EXTERNAL TABLE txt_table_lzo_tst (
   txt_line STRING
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY '||||'
LOCATION '/user/myuser/data/in/lzo_compressed';

The interesting thing is, it works as well, when I execute a SELECT statement and this table.

Can you help, why the second CREATE TABLE statement works as well?
What should I use in DDLs?
Is it best practice to use the STORED AS clause with a "deprecatedLzoTextInputFormat"? Or
should I remove it?


(2) Output and Intermediate Compression Settings

I want to use output compression .

In "Programming Hive" from Capriolo, Wampler, Rutherglen the following commands are recommended:
SET hive.exec.compress.output=true;
SET mapred.output.compression.codec=com.hadoop.compression.lzo.LzopCodec;

          However, in some other places in forums, I found the following recommended settings:
SET hive.exec.compress.output=true
SET mapreduce.output.fileoutputformat.compress=true
SET mapreduce.output.fileoutputformat.compress.codec=com.hadoop.compression.lzo.LzopCodec

Am I right, that the first settings are for Hadoop versions prior 0.23?
Or is there any other reason why the settings are different?

I am using Hadoop 1.1.2 with Hive 0.10.0.
Which settings would you recommend to use?

--------------
          I also want to compress intermediate results.

         Again, in  "Programming Hive" the following settings are recommended:
         SET hive.exec.compress.intermediate=true;
         SET mapred.map.output.compression.codec=com.hadoop.compression.lzo.LzopCodec;

          Is this the right setting?

          Or should I again use the settings (which look more valid for Hadoop 0.23 and greater)?:
          SET hive.exec.compress.intermediate=true;
          SET mapreduce.map.output.compression.codec=com.hadoop.compression.lzo.LzopCodec;

Thanks




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