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[appendix]
[[faq]]
== FAQ
:doctype: book
:numbered:
:toc: left
:icons: font
:experimental:

=== General
When should I use HBase?::
  See <<arch.overview>> in the Architecture chapter.

Are there other HBase FAQs?::
  See the FAQ that is up on the wiki, link:https://wiki.apache.org/hadoop/Hbase/FAQ[HBase Wiki FAQ].

Does HBase support SQL?::
  Not really. SQL-ish support for HBase via link:https://hive.apache.org/[Hive] is in development, however Hive is based on MapReduce which is not generally suitable for low-latency requests. See the <<datamodel>> section for examples on the HBase client.

How can I find examples of NoSQL/HBase?::
  See the link to the BigTable paper in <<other.info>>, as well as the other papers.

What is the history of HBase?::
  See <<hbase.history,hbase.history>>.

Why are the cells above 10MB not recommended for HBase?::
  Large cells don't fit well into HBase's approach to buffering data. First, the large cells bypass the MemStoreLAB when they are written. Then, they cannot be cached in the L2 block cache during read operations. Instead, HBase has to allocate on-heap memory for them each time. This can have a significant impact on the garbage collector within the RegionServer process.

=== Upgrading
How do I upgrade Maven-managed projects from HBase 0.94 to HBase 0.96+?::
  In HBase 0.96, the project moved to a modular structure. Adjust your project's dependencies to rely upon the `hbase-client` module or another module as appropriate, rather than a single JAR. You can model your Maven dependency after one of the following, depending on your targeted version of HBase. See Section 3.5, “Upgrading from 0.94.x to 0.96.x” or Section 3.3, “Upgrading from 0.96.x to 0.98.x” for more information.
+
.Maven Dependency for HBase 0.98
[source,xml]
----
<dependency>
  <groupId>org.apache.hbase</groupId>
  <artifactId>hbase-client</artifactId>
  <version>0.98.5-hadoop2</version>
</dependency>
----
+
.Maven Dependency for HBase 0.96
[source,xml]
----
<dependency>
  <groupId>org.apache.hbase</groupId>
  <artifactId>hbase-client</artifactId>
  <version>0.96.2-hadoop2</version>
</dependency>
----
+
.Maven Dependency for HBase 0.94
[source,xml]
----
<dependency>
  <groupId>org.apache.hbase</groupId>
  <artifactId>hbase</artifactId>
  <version>0.94.3</version>
</dependency>
----


=== Architecture
How does HBase handle Region-RegionServer assignment and locality?::
  See <<regions.arch>>.

=== Configuration
How can I get started with my first cluster?::
  See <<quickstart>>.

Where can I learn about the rest of the configuration options?::
  See <<configuration>>.

=== Schema Design / Data Access

How should I design my schema in HBase?::
  See <<datamodel>> and <<schema>>.

How can I store (fill in the blank) in HBase?::
  See <<supported.datatypes>>.

How can I handle secondary indexes in HBase?::
  See <<secondary.indexes>>.

Can I change a table's rowkeys?::
  This is a very common question. You can't. See <<changing.rowkeys>>.

What APIs does HBase support?::
  See <<datamodel>>, <<architecture.client>>, and <<external_apis>>.

=== MapReduce

How can I use MapReduce with HBase?::
  See <<mapreduce>>.

=== Performance and Troubleshooting

How can I improve HBase cluster performance?::
  See <<performance>>.

How can I troubleshoot my HBase cluster?::
  See <<trouble>>.

=== Amazon EC2

I am running HBase on Amazon EC2 and...::
  EC2 issues are a special case. See <<trouble.ec2>> and <<perf.ec2>>.

=== Operations

How do I manage my HBase cluster?::
  See <<ops_mgt>>.

How do I back up my HBase cluster?::
  See <<ops.backup>>.

=== HBase in Action

Where can I find interesting videos and presentations on HBase?::
  See <<other.info>>.

:numbered:
