What is Modeling data in Hadoop and how to do it

0 votes
Currently I am bringing into Hadoop around 10 tables from an EDW (Enterprise Data Warehouse), these tables are closely related to a Star Schema model. I'm using Sqoop to bring all these tables across, resulting in 10 directories containing csv files.

I'm looking at what are some better ways to store these files before striking off MR jobs. Should I follow some kind of model or build an aggregate before working on MR jobs? I'm basically looking at how might be some ways of storing related data together.

Most things I have found by searching are storing trivial csv files and reading them with opencsv. I'm looking for something a bit more involved and not just for csv files. If moving towards another format works better than csv, then that is no problem.

Boils down to: How best to store a bunch of related data in HDFS to have a good experience with MR.
Sep 19, 2018 in Big Data Hadoop by Neha
• 6,300 points
1,561 views

1 answer to this question.

0 votes
I suggest spending some time with Apache Avro.

With Sqoop v1.3 and beyond you can import data from your relational data sources as Avro files using a schema of your own design. What's nice about Avro is that it provides a lot of features in addition to being a serialization format...

It gives you data+schema in the same file but is compact and efficient for fast serialization. It gives you versioning facilities which are useful when bringing in updated data with a different schema. Hive supports it in both reading and writing and Map Reduce can use it seamlessly.

It can be used as a generic interchange format between applications (not just for Hadoop) making it an interesting option for a standard, cross-platform format for data exchange in your broader architecture.

Even this way it works fine..

Storing these files in csv is fine. Since you will be able to process these files using text output format and could also read it through hive using specific delimiter. You could change the delimiter if you do not like comma to pipe("|") that's what I do most of the time. Also you generally need to have large files in hadoop but if its large enough that you can partition these files and each file partition is in the size of few 100 gigs then it would be a good to partition these files into separate directory based on your partition column.

Also it would be better idea to have most of the columns in single table than having many normalized small tables. But that varies depending on your data size. Also make sure whenever you copy , move or create data you do all the constraint check on your applications as it will be difficult to make small changes in the table later on, you will need to modify the complete file for even small change.
answered Sep 19, 2018 by Frankie
• 9,830 points

Related Questions In Big Data Hadoop

0 votes
1 answer

I have to ingest in hadoop cluster large number of files for testing , what is the best way to do it?

Hi@sonali, It depends on what kind of testing ...READ MORE

answered Jul 8, 2020 in Big Data Hadoop by MD
• 95,440 points
938 views
0 votes
11 answers
0 votes
1 answer

What is -cp command in hadoop? How it works?

/user/cloudera/data1 is not a directory, it is ...READ MORE

answered Oct 17, 2018 in Big Data Hadoop by Frankie
• 9,830 points
3,825 views
+1 vote
1 answer

Hadoop Mapreduce word count Program

Firstly you need to understand the concept ...READ MORE

answered Mar 16, 2018 in Data Analytics by nitinrawat895
• 11,380 points
10,560 views
+2 votes
11 answers

hadoop fs -put command?

Hi, You can create one directory in HDFS ...READ MORE

answered Mar 16, 2018 in Big Data Hadoop by nitinrawat895
• 11,380 points
104,218 views
–1 vote
1 answer

Hadoop dfs -ls command?

In your case there is no difference ...READ MORE

answered Mar 16, 2018 in Big Data Hadoop by kurt_cobain
• 9,390 points
4,261 views
0 votes
1 answer
0 votes
1 answer

What is the Data format and database choices in Hadoop and Spark?

Use Parquet. I'm not sure about CSV ...READ MORE

answered Sep 4, 2018 in Big Data Hadoop by Frankie
• 9,830 points
716 views
0 votes
1 answer

What is Custom partitioner in Hadoop? How to write partition function ?

Don't think that in Hadoop the same ...READ MORE

answered Sep 18, 2018 in Big Data Hadoop by Frankie
• 9,830 points
1,356 views
webinar REGISTER FOR FREE WEBINAR X
REGISTER NOW
webinar_success Thank you for registering Join Edureka Meetup community for 100+ Free Webinars each month JOIN MEETUP GROUP