HBase: The Definitive Guide

Chapter 5. Client API: Administrative Features

Apart from the client API used to deal with data manipulation features, HBase also exposes a data definition-like API. This is similar to the separation into DDL and DML found in RDBMSes. First we will look at the classes required to define the data schemas and subsequently see the API that makes use of it to, for example, create a new HBase table.

Schema Definition

Creating a table in HBase implicitly involves the definition of a table schema, as well as the schemas for all contained column families. They define the pertinent characteristics of how—and when—the data inside the table and columns is ultimately stored.

Tables

Everything stored in HBase is ultimately grouped into one or more tables. The primary reason to have tables is to be able to control certain features that all columns in this table share. The typical things you will want to define for a table are column families. The constructor of the table descriptor in Java looks like the following:

HTableDescriptor();
HTableDescriptor(String name);
HTableDescriptor(byte[] name);
HTableDescriptor(HTableDescriptor desc);

Writable and the Parameterless Constructor

You will find that most classes provided by the API and discussed throughout this chapter do possess a special constructor, one that does not take any parameters. This is attributed to these classes implementing the Hadoop Writable interface.

Every communication between remote disjoint systems—for example, the client talking to ...