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From bejo...@gmail.com
Subject Re: denormalize data during import
Date Sun, 21 Aug 2011 19:33:46 GMT
Hi Srivathsan
          I did get your requirement and if you are in for developing a map reduce program,
may be you can achieve the same in two steps.
1. SQOOP Import data into HDFS
2. Use a custom map reduce to de normalize the same.
     In your map reduce join the two data sets using the foreign key. For this

In Mapper
-Use Multiple Input Format to parse the two different inputs
-project the data in each mapper with key as the foreign key and the value as the combination
of required column values in each case
-prefix an identifier to identify the source of the values in the reducer

In Reducer
- the identifier helps to know the source of data(which table the data is from)
- Append the data from different sources as required(choose output key value as required)

The solution is a crude one and has its flaws. Just scribbled a possible solution from my
limited expertise.
 
Experts, please share some sophisticated approach which you feel is optimal in handling such
requirements.

Regards
Bejoy K S

-----Original Message-----
From: Srivathsan Srinivas <periya.data@gmail.com>
Date: Sat, 20 Aug 2011 23:06:06 
To: <sqoop-user@incubator.apache.org>
Reply-To: sqoop-user@incubator.apache.org
Subject: denormalize data during import

Hi,
   I am looking for a way to denormalize my tables when I am importing from
MySQL to HDFS/HIVE. What is the best approach? Is there a way to add columns
dynamically when using Sqoop or any other means?

For eg., an RDBMS table of students might have student name and address(es).
This may be a normalized form in different tables. What I want during my
import process is a single row for each student where there will be multiple
columns for all the addresses for a given student (like addr_1, addr_2,
...etc). I can write UDFs for it, but, do not know how to attach it to
sqoop. I undertand that sqoop can add SQL queries (such as join) before
importing. But, that will add more rows. I want a single row with multiple
columns.

Should I have UDFs in Sqoop or Oozie in my workflow and denormalize them on
the fly? I have not tried it. Is there any suggested approach? I am
beginning to look at Solr's DataImportHandler...perhaps that could solve
this.

Suggestions are appreciated.

Thanks,
PD.

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