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Subject: Re: HBase (BigTable) many to many with students and courses
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From: Michel Segel <michael_segel@hotmail.com>
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Date: Tue, 29 May 2012 05:39:39 -0500
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Depends...
Try looking at a hierarchical model rather than a relational model...

One thing to remember is that joins are expensive in HBase.


Sent from a remote device. Please excuse any typos...

Mike Segel

On May 28, 2012, at 12:50 PM, Em <mailformailinglists@yahoo.de> wrote:

> Hello list,
> 
> I have some time now to try out HBase and want to use it for a private
> project.
> 
> Questions like "How to I transfer one-to-many or many-to-many relations
> from my RDBMS's schema to HBase?" seem to be common.
> 
> I hope we can throw all the best practices that are out there in this
> thread.
> 
> As the wiki states:
> One should create two tables.
> One for students, another for courses.
> 
> Within the students' table, one should add one column per selected
> course with the course_id besides some columns for the student itself
> (name, birthday, sex etc.).
> 
> On the other hand one fills the courses table with one column per
> student_id besides some columns which describe the course itself (name,
> teacher, begin, end, year, location etc.).
> 
> So far, so good.
> 
> How do I access these tables efficiently?
> 
> A common case would be to show all courses per student.
> 
> To do so, one has to access the student-table and get all the student's
> courses-columns.
> Let's say their names are prefixed ids. One has to remove the prefix and
> then one accesses the courses-table to get all the courses and their
> metadata (name, teacher, location etc.).
> 
> How do I do this kind of operation efficiently?
> The naive and brute force approach seems to be using a Get-object per
> course and fetch the neccessary data.
> Another approach seems to be using the HTable-class and unleash the
> power of "multigets" by using the batch()-method.
> 
> All of the information above is theoretically, since I did not used it
> in code (I currently learn more about the fundamentals of HBase).
> 
> That's why I give the question to you: How do you do this kind of
> operation by using HBase?
> 
> Kind regards,
> Em
>