Drizzle (database server)
|This article relies on references to primary sources. (February 2011)|
|Developer(s)||Brian Aker and others|
|Stable release||7.1.36 / May 23, 2012|
|Operating system||Cross-platform POSIX|
|Available in||English, with GNU Gettext translations into 43 other languages|
|Type||Database management system|
|License||Primarily GNU General Public License version 2 and 3, with some BSD components|
Like MySQL, Drizzle has a client/server architecture and uses SQL as its primary command language. Drizzle is distributed under version 2 and 3 of the GNU General Public License (GPL) with portions, including the protocol drivers and replication messaging under the BSD license.
Early work on the fork was done mid-2008 by Brian Aker. Ongoing development is handled by a team of contributors that includes staff members from Canonical Ltd., Google, Six Apart, Sun Microsystems, Rackspace, Data Differential, Blue Gecko, Intel, Percona, Hewlett-Packard, Red Hat, and others. Drizzle source code, along with instructions on compiling it, are available via the project's Launchpad website.
In October 2010, Drizzle had 13,478 total contributions, 96 total contributors, and 37 active contributors. It was also announced that Drizzle had entered Beta,. The first GA version was released in March 2011. Drizzle has actively participated in the Google Summer of Code Project in 2010, in 2011 , in 2012 , and in 2013 
Platforms and interfaces 
Drizzle is written in the C++ programming language, and stores its string data in the UTF-8 format. It is being developed for modern Unix-like operating systems, including Linux, FreeBSD, Mac OS X, and Solaris – in general, any OS that conforms to POSIX and has a working implementation of the GNU Autotools. Microsoft Windows is not supported at this time, mainly for lack of Autotools support, but there has been discussion of how to accomplish this in a sensible manner.
Drizzle is a re-designed version of the MySQL v6.0 codebase and is designed around a central concept of having a microkernel architecture. Features such as the query cache and authentication system are now plugins to the database, which follow the general theme of "pluggable storage engines" that were introduced in MySQL 5.1. It supports PAM, LDAP, and HTTP AUTH for authentication via plugins it ships. Via its plugin system it currently supports logging to files, syslog, and remote services such as RabbitMQ and Gearman. Drizzle is an ACID-compliant relational database that supports transactions via an MVCC design.
Like MySQL, Drizzle supports concurrent multiple engines. Via this, Drizzle includes built-in support for B+ tree and Hash indexes. Drizzle's query planner is capable of using multiple indexes, from multiple engines to satisfy complex queries, using temporary in-memory bitmap index operations.
Database triggers in Drizzle are supported for DML, DDL, and a number of additional event-based operations in the server. The PrimeBase BLOB streaming system, which allows Drizzle to stream binary large objects (BLOBs) via HTTP, makes use of this system. All triggers for Drizzle currently must be written in C++.
Query rewrite 
Any query can be matched and rewritten dynamically that is sent to the server. This action is done before parsing occurs.
Data types 
A wide variety of native data types are supported, including:
- Variable-length arrays (including text and composite types) up to 4 GB in total storage size
- Arbitrary precision numerics
- An enumerated type (enum) that supports current 10,000 types
Dynamic SQL 
Through support of the EXECUTE command Drizzle can operate dynamic multi-statement SQL. Via the keyword CONCURRENT it can operate these statements in parallel.
Replication in Drizzle is done by generating "messages" using the Google Protocol Buffers library. These messages are then stored and executed on remote servers. The message format is a non-SQL neutral format which has allowed Drizzle to have replication appliers to RabbitMQ, Memcached, MySQL, Voldemort, and Apache Cassandra.
Support and licensing 
Drizzle is licensed under version two and three of the GPL, with some parts, such as libdrizzle client library, under the BSD license.
See also 
- Drizzle History[dead link]
- List of Drizzle Contributors
- How Many Contributors does Drizzle Have?
- Drizzle7 Beta Released
- Drizzle Documentation
- Official website
- Brian Aker's "What If?" article on Drizzle
- Michael Widenius's "What If" article on Drizzle
- FLOSS interview with Brian on the future direction of Drizzle
- Drizzle (database server) at Freecode