Cleaned up docs/databases.txt
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Adrian Holovaty
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===============================
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Notes About Supported Databases
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Notes about supported databases
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===============================
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Django attempts to support as many features as possible on all databases.
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However, since not all database servers are identical, there is obviously
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going to be some variations. This file describes some of the
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features that might relevant to Django usage. It is not intended as a
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replacement for server-specific documentation or reference manuals.
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Django attempts to support as many features as possible on all database
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backends. However, not all database backends are alike, and we've had to make
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design decisions on which features to support and which assumptions we can make
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safely.
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MySQL Notes
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This file describes some of the features that might be relevant to Django
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usage. Of course, it is not intended as a replacement for server-specific
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documentation or reference manuals.
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MySQL notes
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===========
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Django expects the database to support transactions, referential integrity,
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and Unicode support (UTF-8 encoding). Fortunately MySQL_ has all these
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and Unicode support (UTF-8 encoding). Fortunately, MySQL_ has all these
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features as available as far back as 3.23. While it may be possible to use
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3.23 or 4.0, you will probably have less trouble if you use 4.1 or 5.0.
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3.23 or 4.0, you'll probably have less trouble if you use 4.1 or 5.0.
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MySQL-4.1
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MySQL 4.1
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---------
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MySQL-4.1_ has greatly improved support for character sets. It is possible to
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`MySQL 4.1`_ has greatly improved support for character sets. It is possible to
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set different default character sets on the database, table, and column.
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Previous versions have only a server-wide character set setting. It's also the
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first version where the character set can be changed on the fly. 4.1 also has
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support for views, but these are not currently used by Django.
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support for views, but Django currently doesn't use views.
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MySQL-5.0
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MySQL 5.0
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---------
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MySQL-5.0_ adds the ``information_schema`` database, which contains detailed
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data on all database schema. This is used for Django's ``inspectdb`` feature,
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when it is available. 5.0 also has support for stored procedures, but these
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are not currently used by Django.
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`MySQL 5.0`_ adds the ``information_schema`` database, which contains detailed
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data on all database schema. Django's ``inspectdb`` feature uses this
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``information_schema`` if it's available. 5.0 also has support for stored
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procedures, but Django currently doesn't use stored procedures.
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.. _MySQL: http://www.mysql.com/
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.. _MySQL-4.1: http://dev.mysql.com/doc/refman/4.1/en/index.html
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.. _MySQL-5.0: http://dev.mysql.com/doc/refman/5.0/en/index.html
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.. _MySQL 4.1: http://dev.mysql.com/doc/refman/4.1/en/index.html
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.. _MySQL 5.0: http://dev.mysql.com/doc/refman/5.0/en/index.html
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Storage Engines
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Storage engines
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---------------
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MySQL has several `storage engines`_ (previously called table types). You can
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change the default storage engine in the server configuration.
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The default one is MyISAM_. The main drawback of MyISAM is that it does not
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currently have support for transactions or foreign keys. On the plus side, it
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is currently the only engine that supports full-text indexing and searching.
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The default engine is MyISAM_. The main drawback of MyISAM is that it doesn't
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currently support transactions or foreign keys. On the plus side, it's
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currently the only engine that supports full-text indexing and searching.
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The InnoDB_ engine is fully transactional and supports foreign key references.
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The BDB_ engine, like InnoDB, is also fully transactional and supports foreign
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key references. However, it's use seems to be somewhat deprecated.
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key references. However, its use seems to be deprecated.
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`Other storage engines`_, including SolidDB_ and Falcon_, are on the horizon.
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For now, InnoDB is probably your best choice.
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@ -66,25 +69,25 @@ For now, InnoDB is probably your best choice.
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MySQLdb
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-------
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`MySQLdb`_ is the Python interface to MySQL. 1.2.1 is the first version which
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has support for MySQL-4.1 and newer. If you are trying to use an older version
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of MySQL, then 1.2.0 *may* work for you.
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`MySQLdb`_ is the Python interface to MySQL. 1.2.1 is the first version that
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has support for MySQL 4.1 and newer. If you are trying to use an older version
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of MySQL, then 1.2.0 *might* work for you.
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.. _MySQLdb: http://sourceforge.net/projects/mysql-python
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Creating your database
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~~~~~~~~~~~~~~~~~~~~~~
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----------------------
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You can `create your database`_ using the command-line tools and this SQL::
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CREATE DATABASE <dbname> CHARACTER SET utf8;
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This ensures all tables and columns will use utf8 by default.
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This ensures all tables and columns will use UTF-8 by default.
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.. _create your database: http://dev.mysql.com/doc/refman/5.0/en/create-database.html
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Connecting to the database
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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--------------------------
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Refer to the `settings documentation`_.
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@ -114,8 +117,8 @@ Here's a sample configuration which uses a MySQL option file::
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passwd = DATABASE_PASSWORD
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default-character-set = utf8
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There are several other MySQLdb connection options which may be useful, such
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as ``ssl``, ``use_unicode``, ``init_command``, and ``sql_mode``; consult the
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Several other MySQLdb connection options may be useful, such as ``ssl``,
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``use_unicode``, ``init_command``, and ``sql_mode``. Consult the
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`MySQLdb documentation`_ for more details.
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.. _settings documentation: http://www.djangoproject.com/documentation/settings/#database-engine
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@ -123,40 +126,37 @@ as ``ssl``, ``use_unicode``, ``init_command``, and ``sql_mode``; consult the
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.. _MySQLdb documentation: http://mysql-python.sourceforge.net/
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Creating your tables
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~~~~~~~~~~~~~~~~~~~~
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--------------------
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When Django generates the schema, it doesn't specify a storage engine, so they
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will be created with whatever default `storage engine`__ your database server
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is configured for. The easiest solution is to set your database server's default
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storage engine to the desired engine.
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When Django generates the schema, it doesn't specify a storage engine, so
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tables will be created with whatever default storage engine your database
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server is configured for. The easiest solution is to set your database server's
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default storage engine to the desired engine.
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__ `storage engines`_
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If you are using a hosting service and can't change your server's default
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If you're using a hosting service and can't change your server's default
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storage engine, you have a couple of options.
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After the tables is created, all that is needed to convert it to a new storage
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engine (such as InnoDB) is::
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* After the tables are created, execute an ``ALTER TABLE`` statement to
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convert a table to a new storage engine (such as InnoDB)::
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ALTER TABLE <tablename> ENGINE=INNODB;
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ALTER TABLE <tablename> ENGINE=INNODB;
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With a lot of tables, this can be tedious.
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This can be tedious if you have a lot of tables.
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Another option is to use the ``init_command`` option for MySQLdb prior to
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creating your tables::
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* Another option is to use the ``init_command`` option for MySQLdb prior to
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creating your tables::
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DATABASE_OPTIONS = {
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...
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"init_command": "SET storage_engine=INNODB",
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...
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}
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DATABASE_OPTIONS = {
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# ...
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"init_command": "SET storage_engine=INNODB",
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# ...
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}
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This sets the default storage engine upon connecting to the database. After
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your tables are set up and running in production, you should remove this
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option.
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This sets the default storage engine upon connecting to the database.
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After your tables have been created, you should remove this option.
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Another method for changing the storage engine is described in
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AlterModelOnSyncDB_.
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* Another method for changing the storage engine is described in
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AlterModelOnSyncDB_.
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.. _AlterModelOnSyncDB: http://code.djangoproject.com/wiki/AlterModelOnSyncDB
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