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Hive, mail # user - Noob question on creating tables


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Re: Noob question on creating tables
Sanjay Subramanian 2013-03-29, 19:45
I agree. BASH is super easy for things like this

I have a daily alter partition script I call thru a java-action in Oozie (that Java class calls a HiveClient interface implementation)
Example script that I run for us where date and server are partitions
for r in $(hdfs dfs -ls  /path/to/directory/in/hdfs |awk '{print $8}')
  do
    datestr=$(echo $r|cut -d "/" -f 10)
    serverstr=$(echo $r|cut -d "/" -f 11)
    $HIVE_HOME/bin/hive -hiveconf hive.root.logger=INFO,console -e "ALTER TABLE my_table ADD PARTITION (header_date='$datestr' , header_servername='$serverstr') LOCATION '$r';"
done

From: Dean Wampler <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Reply-To: "[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>" <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Date: Friday, March 29, 2013 11:37 AM
To: "[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>" <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>
Subject: Re: Noob question on creating tables

That's a drawback of external tables, but it's actually not as difficult as it sounds. It's easy to write a nightly "cron" job that creates the partition for the next day (or a job per month...), if someone on your team has some bash experience. Other job scheduling tools should support this too. Here's an example. First, a hive script that uses parameters for the date (Hive v0.8 or newer):

-- addlogpartition.hql
ALTER TABLE log ADD IF NOT EXISTS PARTITION (year = ${YEAR}, month = ${MONTH}, day = ${DAY});

Then, run this bash script AFTER MIDNIGHT:

#!/bin/bash
YEAR=$(date +%Y)       # returns the string "2013" today.
MONTH=$(date +%m)   # returns the string "03" today, with the leading zero.
DAY=$(date +%d)          # returns the string "29" today. Will prefix with 0 for dates < 10.

# Assumes /path/to/2013/03/29 is the correct directory name:
/path/to/hive -f /path/to/addlogpartition.hql -d YEAR=$YEAR -d MON=$MONTH -d DAY=$DAY
(Of course, all the /path/to will be different...)

So, be careful of how how "03" vs. "3" is handled in both the ALTER TABLE statement and the path. Off hand, I don't know if Hive will complain if you use 03 as an integer value in the ALTER TABLE statement.
On Fri, Mar 29, 2013 at 1:16 PM, Mark <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:
Thanks

Does this mean I need to create a partition for each day manually? There is no way to have infer that from my directory structure?

On Mar 29, 2013, at 10:40 AM, Sanjay Subramanian <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:

> Hi
>
> CREATE EXTERNAL TABLE IF NOT EXISTS log_data(col1 datatype1, col2
> datatype2, . . . colN datatypeN) PARTITIONED BY (YEAR INT, MONTH INT, DAY
> INT) ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t';
>
>
> ALTER table log_data ADD PARTITION (YEAR=2013 , MONTH=2, DAY=27) LOCATION
> '/path/to/YEAR/MONTH/DAY/directory/ON/HDFS';"
>
> Hive will read gzip and bz2 files out of the box.(so suppose you had
> hourly log files in gzip format in your /YEAR/MONTH/DAY directory then it
> will be read)
> Snappy and LZO will need some jar installs and configs
> https://github.com/toddlipcon/hadoop-lzo
>
> https://code.google.com/p/snappy/
>
>
> Note that for example - gzip format is not splittable..so huge gzip files
> without splits are not recommended as input to maps
>
> Hope this helps
>
> sanjay
>
>
> On 3/29/13 10:19 AM, "Mark" <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:
>
>> We have existing log data in directories in the format of YEAR/MONTH/DAY.
>>
>> - How can we create a table over this table without hive modifying and/or
>> moving it?
>> - How can we tell Hive to partition this data so it knows about each day
>> of logs?
>> - Does hive out of the box work with reading compressed files?
>>
>> Thanks
>
>
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Dean Wampler, Ph.D.
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