Database Reference
In-Depth Information
Now you've retrieved the two rows using an efficient range scan, but how do you compute
the average? In the HBase shell, it's not possible; using the HBase Java APIs, you can extract
the values, but there is no built-in row aggregation function for average or sum, so you
would need to do this in your Java code.
The choice of the row key is critical in HBase. If you want to find the average rating of all
the movies Kevin has reviewed, you would need to do a full table scan, potentially a very te-
dious task with a very large dataset. You might want to have two versions of the table, one
with the row key given by reviewer-film and another with film-reviewer. Then you would
have the problem of ensuring they're in sync.
Accumulo
License
Apache License, Version 2.0
Activity
High
Purpose
Name-value database with cell-level security
Official Page
Hadoop Integration Fully Integrated
You have an application that could use a good column/name-value store, like HBase (de-
scribed
here
), but you have an additional security issue; you must carefully control which
users can see which cells in your data. For example, you could have a multitenancy data
store in which you are storing data from different divisions in your enterprise in a single
table and want to ensure that users from one division cannot see the data from another, but
that senior management can see across the whole enterprise. For internal security reasons, the
U.S. National Security Agency (NSA) developed Accumulo and then donated the code to the
Apache foundation.
