More migration docs, and conversion of all easy syncdb references

This commit is contained in:
Andrew Godwin 2013-07-25 16:19:36 +01:00
parent 06103c8ef5
commit f8297f6323
24 changed files with 172 additions and 67 deletions

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@ -81,10 +81,10 @@ access to your precious data on a model by model basis.
Install the core Django tables Install the core Django tables
============================== ==============================
Next, run the :djadmin:`syncdb` command to install any extra needed database Next, run the :djadmin:`migrate` command to install any extra needed database
records such as admin permissions and content types:: records such as admin permissions and content types::
python manage.py syncdb python manage.py migrate
Test and tweak Test and tweak
============== ==============

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@ -165,9 +165,9 @@ __ http://sphinx.pocoo.org/markup/desc.html
* ``django-admin`` commands:: * ``django-admin`` commands::
.. django-admin:: syncdb .. django-admin:: migrate
To link, use ``:djadmin:`syncdb```. To link, use ``:djadmin:`migrate```.
* ``django-admin`` command-line options:: * ``django-admin`` command-line options::

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@ -53,10 +53,11 @@ automatically:
.. code-block:: bash .. code-block:: bash
manage.py syncdb manage.py migrate
The :djadmin:`syncdb` command looks at all your available models and creates The :djadmin:`migrate` command looks at all your available models and creates
tables in your database for whichever tables don't already exist. tables in your database for whichever tables don't already exist, as well as
optionally providing :doc:`much richer schema control </topics/migrations>`.
Enjoy the free API Enjoy the free API
================== ==================

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@ -155,7 +155,7 @@ this. For a small app like polls, this process isn't too difficult.
url(r'^polls/', include('polls.urls')), url(r'^polls/', include('polls.urls')),
3. Run `python manage.py syncdb` to create the polls models. 3. Run `python manage.py migrate` to create the polls models.
4. Start the development server and visit http://127.0.0.1:8000/admin/ 4. Start the development server and visit http://127.0.0.1:8000/admin/
to create a poll (you'll need the Admin app enabled). to create a poll (you'll need the Admin app enabled).

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@ -45,8 +45,7 @@ Outputs to standard output all data in the database associated with the named
application(s). application(s).
.TP .TP
.BI flush .BI flush
Returns the database to the state it was in immediately after syncdb was Removes all data from the database and then re-installs any initial data.
executed.
.TP .TP
.B inspectdb .B inspectdb
Introspects the database tables in the database specified in settings.py and outputs a Django Introspects the database tables in the database specified in settings.py and outputs a Django
@ -114,9 +113,9 @@ the current directory or the optional destination.
Creates a Django project directory structure for the given project name Creates a Django project directory structure for the given project name
in the current directory or the optional destination. in the current directory or the optional destination.
.TP .TP
.BI syncdb .BI migrate
Creates the database tables for all apps in INSTALLED_APPS whose tables Runs migrations for apps containing migrations, and just creates missing tables
haven't already been created. for apps without migrations.
.TP .TP
.BI "test [" "\-\-verbosity" "] [" "\-\-failfast" "] [" "appname ..." "]" .BI "test [" "\-\-verbosity" "] [" "\-\-failfast" "] [" "appname ..." "]"
Runs the test suite for the specified applications, or the entire project if Runs the test suite for the specified applications, or the entire project if

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@ -31,7 +31,7 @@ To get started using the ``comments`` app, follow these steps:
#. Install the comments framework by adding ``'django.contrib.comments'`` to #. Install the comments framework by adding ``'django.contrib.comments'`` to
:setting:`INSTALLED_APPS`. :setting:`INSTALLED_APPS`.
#. Run ``manage.py syncdb`` so that Django will create the comment tables. #. Run ``manage.py migrate`` so that Django will create the comment tables.
#. Add the comment app's URLs to your project's ``urls.py``: #. Add the comment app's URLs to your project's ``urls.py``:

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@ -86,7 +86,7 @@ The ``ContentType`` model
Let's look at an example to see how this works. If you already have Let's look at an example to see how this works. If you already have
the :mod:`~django.contrib.contenttypes` application installed, and then add the :mod:`~django.contrib.contenttypes` application installed, and then add
:mod:`the sites application <django.contrib.sites>` to your :mod:`the sites application <django.contrib.sites>` to your
:setting:`INSTALLED_APPS` setting and run ``manage.py syncdb`` to install it, :setting:`INSTALLED_APPS` setting and run ``manage.py migrate`` to install it,
the model :class:`django.contrib.sites.models.Site` will be installed into the model :class:`django.contrib.sites.models.Site` will be installed into
your database. Along with it a new instance of your database. Along with it a new instance of
:class:`~django.contrib.contenttypes.models.ContentType` will be :class:`~django.contrib.contenttypes.models.ContentType` will be

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@ -55,14 +55,14 @@ or:
3. Add ``'django.contrib.flatpages.middleware.FlatpageFallbackMiddleware'`` 3. Add ``'django.contrib.flatpages.middleware.FlatpageFallbackMiddleware'``
to your :setting:`MIDDLEWARE_CLASSES` setting. to your :setting:`MIDDLEWARE_CLASSES` setting.
4. Run the command :djadmin:`manage.py syncdb <syncdb>`. 4. Run the command :djadmin:`manage.py migrate <migrate>`.
.. currentmodule:: django.contrib.flatpages.middleware .. currentmodule:: django.contrib.flatpages.middleware
How it works How it works
============ ============
``manage.py syncdb`` creates two tables in your database: ``django_flatpage`` ``manage.py migrate`` creates two tables in your database: ``django_flatpage``
and ``django_flatpage_sites``. ``django_flatpage`` is a simple lookup table and ``django_flatpage_sites``. ``django_flatpage`` is a simple lookup table
that simply maps a URL to a title and bunch of text content. that simply maps a URL to a title and bunch of text content.
``django_flatpage_sites`` associates a flatpage with a site. ``django_flatpage_sites`` associates a flatpage with a site.

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@ -15,7 +15,7 @@ those packages have.
For most of these add-ons -- specifically, the add-ons that include either For most of these add-ons -- specifically, the add-ons that include either
models or template tags -- you'll need to add the package name (e.g., models or template tags -- you'll need to add the package name (e.g.,
``'django.contrib.admin'``) to your :setting:`INSTALLED_APPS` setting and ``'django.contrib.admin'``) to your :setting:`INSTALLED_APPS` setting and
re-run ``manage.py syncdb``. re-run ``manage.py migrate``.
.. _"batteries included" philosophy: http://docs.python.org/tutorial/stdlib.html#batteries-included .. _"batteries included" philosophy: http://docs.python.org/tutorial/stdlib.html#batteries-included

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@ -18,12 +18,12 @@ To install the redirects app, follow these steps:
2. Add ``'django.contrib.redirects'`` to your :setting:`INSTALLED_APPS` setting. 2. Add ``'django.contrib.redirects'`` to your :setting:`INSTALLED_APPS` setting.
3. Add ``'django.contrib.redirects.middleware.RedirectFallbackMiddleware'`` 3. Add ``'django.contrib.redirects.middleware.RedirectFallbackMiddleware'``
to your :setting:`MIDDLEWARE_CLASSES` setting. to your :setting:`MIDDLEWARE_CLASSES` setting.
4. Run the command :djadmin:`manage.py syncdb <syncdb>`. 4. Run the command :djadmin:`manage.py migrate <migrate>`.
How it works How it works
============ ============
``manage.py syncdb`` creates a ``django_redirect`` table in your database. This ``manage.py migrate`` creates a ``django_redirect`` table in your database. This
is a simple lookup table with ``site_id``, ``old_path`` and ``new_path`` fields. is a simple lookup table with ``site_id``, ``old_path`` and ``new_path`` fields.
The ``RedirectFallbackMiddleware`` does all of the work. Each time any Django The ``RedirectFallbackMiddleware`` does all of the work. Each time any Django

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@ -264,7 +264,7 @@ To enable the sites framework, follow these steps:
SITE_ID = 1 SITE_ID = 1
3. Run :djadmin:`syncdb`. 3. Run :djadmin:`migrate`.
``django.contrib.sites`` registers a ``django.contrib.sites`` registers a
:data:`~django.db.models.signals.post_syncdb` signal handler which creates a :data:`~django.db.models.signals.post_syncdb` signal handler which creates a

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@ -224,7 +224,7 @@ If you upgrade an existing project to MySQL 5.5.5 and subsequently add some
tables, ensure that your tables are using the same storage engine (i.e. MyISAM tables, ensure that your tables are using the same storage engine (i.e. MyISAM
vs. InnoDB). Specifically, if tables that have a ``ForeignKey`` between them vs. InnoDB). Specifically, if tables that have a ``ForeignKey`` between them
use different storage engines, you may see an error like the following when use different storage engines, you may see an error like the following when
running ``syncdb``:: running ``migrate``::
_mysql_exceptions.OperationalError: ( _mysql_exceptions.OperationalError: (
1005, "Can't create table '\\db_name\\.#sql-4a8_ab' (errno: 150)" 1005, "Can't create table '\\db_name\\.#sql-4a8_ab' (errno: 150)"
@ -663,7 +663,7 @@ required.
.. _`Oracle Database Server`: http://www.oracle.com/ .. _`Oracle Database Server`: http://www.oracle.com/
.. _`cx_Oracle`: http://cx-oracle.sourceforge.net/ .. _`cx_Oracle`: http://cx-oracle.sourceforge.net/
In order for the ``python manage.py syncdb`` command to work, your Oracle In order for the ``python manage.py migrate`` command to work, your Oracle
database user must have privileges to run the following commands: database user must have privileges to run the following commands:
* CREATE TABLE * CREATE TABLE
@ -752,7 +752,7 @@ Oracle imposes a name length limit of 30 characters. To accommodate this, the
backend truncates database identifiers to fit, replacing the final four backend truncates database identifiers to fit, replacing the final four
characters of the truncated name with a repeatable MD5 hash value. characters of the truncated name with a repeatable MD5 hash value.
When running syncdb, an ``ORA-06552`` error may be encountered if When running ``migrate``, an ``ORA-06552`` error may be encountered if
certain Oracle keywords are used as the name of a model field or the certain Oracle keywords are used as the name of a model field or the
value of a ``db_column`` option. Django quotes all identifiers used value of a ``db_column`` option. Django quotes all identifiers used
in queries to prevent most such problems, but this error can still in queries to prevent most such problems, but this error can still

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@ -242,10 +242,8 @@ flush
.. django-admin:: flush .. django-admin:: flush
Returns the database to the state it was in immediately after :djadmin:`syncdb` Removes all data from the database, re-executes any post-synchronization
was executed. This means that all data will be removed from the database, any handlers, and reinstalls any initial data fixtures.
post-synchronization handlers will be re-executed, and the ``initial_data``
fixture will be re-installed.
The :djadminopt:`--noinput` option may be provided to suppress all user The :djadminopt:`--noinput` option may be provided to suppress all user
prompts. prompts.
@ -1293,7 +1291,7 @@ This command is only available if Django's :doc:`authentication system
Creates a superuser account (a user who has all permissions). This is Creates a superuser account (a user who has all permissions). This is
useful if you need to create an initial superuser account but did not useful if you need to create an initial superuser account but did not
do so during ``syncdb``, or if you need to programmatically generate do so during the first ``migrate``, or if you need to programmatically generate
superuser accounts for your site(s). superuser accounts for your site(s).
When run interactively, this command will prompt for a password for When run interactively, this command will prompt for a password for
@ -1379,7 +1377,7 @@ allows for the following options:
Example usage:: Example usage::
django-admin.py syncdb --pythonpath='/home/djangoprojects/myproject' django-admin.py migrate --pythonpath='/home/djangoprojects/myproject'
Adds the given filesystem path to the Python `import search path`_. If this Adds the given filesystem path to the Python `import search path`_. If this
isn't provided, ``django-admin.py`` will use the ``PYTHONPATH`` environment isn't provided, ``django-admin.py`` will use the ``PYTHONPATH`` environment
@ -1394,7 +1392,7 @@ setting the Python path for you.
Example usage:: Example usage::
django-admin.py syncdb --settings=mysite.settings django-admin.py migrate --settings=mysite.settings
Explicitly specifies the settings module to use. The settings module should be Explicitly specifies the settings module to use. The settings module should be
in Python package syntax, e.g. ``mysite.settings``. If this isn't provided, in Python package syntax, e.g. ``mysite.settings``. If this isn't provided,
@ -1408,7 +1406,7 @@ Note that this option is unnecessary in ``manage.py``, because it uses
Example usage:: Example usage::
django-admin.py syncdb --traceback django-admin.py migrate --traceback
By default, ``django-admin.py`` will show a simple error message whenever an By default, ``django-admin.py`` will show a simple error message whenever an
:class:`~django.core.management.CommandError` occurs, but a full stack trace :class:`~django.core.management.CommandError` occurs, but a full stack trace
@ -1424,7 +1422,7 @@ will also output a full stack trace when a ``CommandError`` is raised.
Example usage:: Example usage::
django-admin.py syncdb --verbosity 2 django-admin.py migrate --verbosity 2
Use ``--verbosity`` to specify the amount of notification and debug information Use ``--verbosity`` to specify the amount of notification and debug information
that ``django-admin.py`` should print to the console. that ``django-admin.py`` should print to the console.

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@ -106,9 +106,9 @@ Django quotes column and table names behind the scenes.
.. attribute:: Options.managed .. attribute:: Options.managed
Defaults to ``True``, meaning Django will create the appropriate database Defaults to ``True``, meaning Django will create the appropriate database
tables in :djadmin:`syncdb` and remove them as part of a :djadmin:`flush` tables in :djadmin:`migrate` or as part of migrations and remove them as
management command. That is, Django *manages* the database tables' part of a :djadmin:`flush` management command. That is, Django
lifecycles. *manages* the database tables' lifecycles.
If ``False``, no database table creation or deletion operations will be If ``False``, no database table creation or deletion operations will be
performed for this model. This is useful if the model represents an existing performed for this model. This is useful if the model represents an existing
@ -192,9 +192,9 @@ Django quotes column and table names behind the scenes.
.. admonition:: Changing order_with_respect_to .. admonition:: Changing order_with_respect_to
``order_with_respect_to`` adds an additional field/database column ``order_with_respect_to`` adds an additional field/database column
named ``_order``, so be sure to handle that as you would any other named ``_order``, so be sure to make and apply the appropriate
change to your models if you add or change ``order_with_respect_to`` migrations if you add or change ``order_with_respect_to``
after your initial :djadmin:`syncdb`. after your initial :djadmin:`migrate`.
``ordering`` ``ordering``
------------ ------------

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@ -275,7 +275,7 @@ can or cannot do with Task instances, specific to your application::
) )
The only thing this does is create those extra permissions when you run The only thing this does is create those extra permissions when you run
:djadmin:`manage.py syncdb <syncdb>`. Your code is in charge of checking the :djadmin:`manage.py migrate <migrate>`. Your code is in charge of checking the
value of these permissions when an user is trying to access the functionality value of these permissions when an user is trying to access the functionality
provided by the application (viewing tasks, changing the status of tasks, provided by the application (viewing tasks, changing the status of tasks,
closing tasks.) Continuing the above example, the following checks if a user may closing tasks.) Continuing the above example, the following checks if a user may
@ -380,14 +380,12 @@ use as your User model.
Changing :setting:`AUTH_USER_MODEL` has a big effect on your database Changing :setting:`AUTH_USER_MODEL` has a big effect on your database
structure. It changes the tables that are available, and it will affect the structure. It changes the tables that are available, and it will affect the
construction of foreign keys and many-to-many relationships. If you intend construction of foreign keys and many-to-many relationships. If you intend
to set :setting:`AUTH_USER_MODEL`, you should set it before running to set :setting:`AUTH_USER_MODEL`, you should set it before creating
``manage.py syncdb`` for the first time. any migrations or running ``manage.py migrate`` for the first time.
If you have an existing project and you want to migrate to using a custom Changing this setting after you have tables created is not supported
User model, you may need to look into using a migration tool like South_ by :djadmin:`makemigrations` and will result in you having to manually
to ease the transition. write a set of migrations to fix your schema.
.. _South: http://south.aeracode.org
Referencing the User model Referencing the User model
-------------------------- --------------------------

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@ -65,7 +65,7 @@ interactively <auth-admin>`.
Creating superusers Creating superusers
------------------- -------------------
:djadmin:`manage.py syncdb <syncdb>` prompts you to create a superuser the :djadmin:`manage.py migrate <migrate>` prompts you to create a superuser the
first time you run it with ``'django.contrib.auth'`` in your first time you run it with ``'django.contrib.auth'`` in your
:setting:`INSTALLED_APPS`. If you need to create a superuser at a later date, :setting:`INSTALLED_APPS`. If you need to create a superuser at a later date,
you can use a command line utility:: you can use a command line utility::
@ -190,13 +190,13 @@ setting, it will ensure that three default permissions -- add, change and
delete -- are created for each Django model defined in one of your installed delete -- are created for each Django model defined in one of your installed
applications. applications.
These permissions will be created when you run :djadmin:`manage.py syncdb These permissions will be created when you run :djadmin:`manage.py migrate
<syncdb>`; the first time you run ``syncdb`` after adding <migrate>`; the first time you run ``migrate`` after adding
``django.contrib.auth`` to :setting:`INSTALLED_APPS`, the default permissions ``django.contrib.auth`` to :setting:`INSTALLED_APPS`, the default permissions
will be created for all previously-installed models, as well as for any new will be created for all previously-installed models, as well as for any new
models being installed at that time. Afterward, it will create default models being installed at that time. Afterward, it will create default
permissions for new models each time you run :djadmin:`manage.py syncdb permissions for new models each time you run :djadmin:`manage.py migrate
<syncdb>`. <migrate>`.
Assuming you have an application with an Assuming you have an application with an
:attr:`~django.db.models.Options.app_label` ``foo`` and a model named ``Bar``, :attr:`~django.db.models.Options.app_label` ``foo`` and a model named ``Bar``,

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@ -67,7 +67,7 @@ and two items in your :setting:`MIDDLEWARE_CLASSES` setting:
2. :class:`~django.contrib.auth.middleware.AuthenticationMiddleware` associates 2. :class:`~django.contrib.auth.middleware.AuthenticationMiddleware` associates
users with requests using sessions. users with requests using sessions.
With these settings in place, running the command ``manage.py syncdb`` creates With these settings in place, running the command ``manage.py migrate`` creates
the necessary database tables for auth related models, creates permissions for the necessary database tables for auth related models, creates permissions for
any models defined in your installed apps, and prompts you to create any models defined in your installed apps, and prompts you to create
a superuser account the first time you run it. a superuser account the first time you run it.

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@ -77,7 +77,8 @@ application by the :djadmin:`manage.py startapp <startapp>` script),
) )
When you add new apps to :setting:`INSTALLED_APPS`, be sure to run When you add new apps to :setting:`INSTALLED_APPS`, be sure to run
:djadmin:`manage.py syncdb <syncdb>`. :djadmin:`manage.py migrate <migrate>`, optionally making migrations
for them first with :djadmin:`manage.py makemigrations <makemigrations>`.
Fields Fields
====== ======
@ -956,7 +957,7 @@ The reverse name of the ``common.ChildA.m2m`` field will be
reverse name of the ``rare.ChildB.m2m`` field will be ``rare_childb_related``. reverse name of the ``rare.ChildB.m2m`` field will be ``rare_childb_related``.
It is up to you how you use the ``'%(class)s'`` and ``'%(app_label)s`` portion It is up to you how you use the ``'%(class)s'`` and ``'%(app_label)s`` portion
to construct your related name, but if you forget to use it, Django will raise to construct your related name, but if you forget to use it, Django will raise
errors when you validate your models (or run :djadmin:`syncdb`). errors when you validate your models (or run :djadmin:`migrate`).
If you don't specify a :attr:`~django.db.models.ForeignKey.related_name` If you don't specify a :attr:`~django.db.models.ForeignKey.related_name`
attribute for a field in an abstract base class, the default reverse name will attribute for a field in an abstract base class, the default reverse name will
@ -1049,7 +1050,7 @@ are putting those types of relations on a subclass of another model,
you **must** specify the you **must** specify the
:attr:`~django.db.models.ForeignKey.related_name` attribute on each :attr:`~django.db.models.ForeignKey.related_name` attribute on each
such field. If you forget, Django will raise an error when you run such field. If you forget, Django will raise an error when you run
:djadmin:`validate` or :djadmin:`syncdb`. :djadmin:`validate` or :djadmin:`migrate`.
For example, using the above ``Place`` class again, let's create another For example, using the above ``Place`` class again, let's create another
subclass with a :class:`~django.db.models.ManyToManyField`:: subclass with a :class:`~django.db.models.ManyToManyField`::

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@ -44,7 +44,7 @@ Using database-backed sessions
If you want to use a database-backed session, you need to add If you want to use a database-backed session, you need to add
``'django.contrib.sessions'`` to your :setting:`INSTALLED_APPS` setting. ``'django.contrib.sessions'`` to your :setting:`INSTALLED_APPS` setting.
Once you have configured your installation, run ``manage.py syncdb`` Once you have configured your installation, run ``manage.py migrate``
to install the single database table that stores session data. to install the single database table that stores session data.
.. _cached-sessions-backend: .. _cached-sessions-backend:

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@ -122,14 +122,12 @@ database bindings are installed.
* If you're using an unofficial 3rd party backend, please consult the * If you're using an unofficial 3rd party backend, please consult the
documentation provided for any additional requirements. documentation provided for any additional requirements.
If you plan to use Django's ``manage.py syncdb`` command to automatically If you plan to use Django's ``manage.py migrate`` command to automatically
create database tables for your models (after first installing Django and create database tables for your models (after first installing Django and
creating a project), you'll need to ensure that Django has permission to create creating a project), you'll need to ensure that Django has permission to create
and alter tables in the database you're using; if you plan to manually create and alter tables in the database you're using; if you plan to manually create
the tables, you can simply grant Django ``SELECT``, ``INSERT``, ``UPDATE`` and the tables, you can simply grant Django ``SELECT``, ``INSERT``, ``UPDATE`` and
``DELETE`` permissions. On some databases, Django will need ``ALTER TABLE`` ``DELETE`` permissions. After creating a database user with these
privileges during ``syncdb`` but won't issue ``ALTER TABLE`` statements on a
table once ``syncdb`` has created it. After creating a database user with these
permissions, you'll specify the details in your project's settings file, permissions, you'll specify the details in your project's settings file,
see :setting:`DATABASES` for details. see :setting:`DATABASES` for details.

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@ -111,3 +111,113 @@ production environment unless you are very aware of the risks and
its limitations; the support Django ships with is designed to allow its limitations; the support Django ships with is designed to allow
developers to use SQLite on their local machines to develop less complex developers to use SQLite on their local machines to develop less complex
Django projects without the need for a full database. Django projects without the need for a full database.
Workflow
--------
Working with migrations is simple. Make changes to your models - say, add
a field and remove a model - and then run :djadmin:`makemigrations`::
$ python manage.py makemigrations
Migrations for 'books':
0003_auto.py:
- Alter field author on book
Your models will be scanned and compared to the versions currently
contained in your migration files, and then a new set of migrations
will be written out. Make sure to read the output to see what
``makemigrations`` thinks you have changed - it's not perfect, and for
complex changes it might not be detecting what you expect.
Once you have your new migration files, you should apply them to your
database to make sure they work as expected::
$ python manage.py migrate
Operations to perform:
Synchronize unmigrated apps: sessions, admin, messages, auth, staticfiles, contenttypes
Apply all migrations: books
Synchronizing apps without migrations:
Creating tables...
Installing custom SQL...
Installing indexes...
Installed 0 object(s) from 0 fixture(s)
Running migrations:
Applying books.0003_auto... OK
The command runs in two stages; first, it synchronizes unmigrated apps
(performing the same functionality that ``syncdb`` used to provide), and
then it runs any migrations that have not yet been applied.
Once the migration is applied, commit the migration and the models change
to your version control system as a single commit - that way, when other
developers (or your production servers) check out the code, they'll
get both the changes to your models and the accompanying migration at the
same time.
Dependencies
------------
While migrations are per-app, the tables and relationships implied by
your models are too complex to be created for just one app at a time. When
you make a migration that requires something else to run - for example,
you add a ForeignKey in your ``books`` app to your ``authors`` app - the
resulting migration will contain a dependency on a migration in ``authors``.
This means that when you run the migrations, the ``authors`` migration runs
first and creates the table the ForeignKey references, and then the migration
that makes the ForeignKey column runs afterwards and creates the constraint.
If this didn't happen, the migration would try to create the ForeignKey column
without the table it's referencing existing and your database would
throw an error.
This dependency behaviour affects most migration operations where you
restrict to a single app. Restricting to a single app (either in
``makemigrations`` or ``migrate``) is a best-efforts promise, and not
a guarantee; any other apps that need to be used to get dependencies correct
will be.
Migration files
---------------
Migrations are stored as an on-disk format, referred to here as
"migration files". These files are actually just normal Python files with
an agreed-upon object layout, written in a declarative style.
A basic migration file looks like this::
from django.db import migrations, models
class Migration(migrations.Migration):
dependencies = [("migrations", "0001_initial")]
operations = [
migrations.DeleteModel("Tribble"),
migrations.AddField("Author", "rating", models.IntegerField(default=0)),
]
What Django looks for when it loads a migration file (as a Python module) is
a subclass of ``django.db.migrations.Migration`` called ``Migration``. It then
inspects this object for four attributes, only two of which are used
most of the time:
* ``dependencies``, a list of migrations this one depends on.
* ``operations``, a list of Operation classes that define what this migration
does.
The operations are the key; they are a set of declarative instructions which
tell Django what schema changes need to be made. Django scans them and
builds an in-memory representation of all of the schema changes to all apps,
and uses this to generate the SQL which makes the schema changes.
That in-memory structure is also used to work out what the differences are
between your models and the current state of your migrations; Django runs
through all the changes, in order, on an in-memory set of models to come
up with the state of your models last time you ran ``makemigrations``. It
then uses these models to compare against the ones in your ``models.py`` files
to work out what you have changed.
You should rarely, if ever, need to edit migration files by hand, but
it's entirely possible to write them manually if you need to. Some of the
more complex operations are not autodetectable and are only available via
a hand-written migration, so don't be scared about editing them if you have to.

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@ -296,7 +296,7 @@ serialize an object that refers to a content type, then you need to have a way
to refer to that content type to begin with. Since ``ContentType`` objects are to refer to that content type to begin with. Since ``ContentType`` objects are
automatically created by Django during the database synchronization process, automatically created by Django during the database synchronization process,
the primary key of a given content type isn't easy to predict; it will the primary key of a given content type isn't easy to predict; it will
depend on how and when :djadmin:`syncdb` was executed. This is true for all depend on how and when :djadmin:`migrate` was executed. This is true for all
models which automatically generate objects, notably including models which automatically generate objects, notably including
:class:`~django.contrib.auth.models.Permission`, :class:`~django.contrib.auth.models.Permission`,
:class:`~django.contrib.auth.models.Group`, and :class:`~django.contrib.auth.models.Group`, and

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@ -278,7 +278,7 @@ testing behavior. This behavior involves:
#. Creating the test databases. #. Creating the test databases.
#. Running ``syncdb`` to install models and initial data into the test #. Running ``migrate`` to install models and initial data into the test
databases. databases.
#. Running the tests that were found. #. Running the tests that were found.
@ -469,7 +469,7 @@ can be useful during testing.
.. function:: create_test_db([verbosity=1, autoclobber=False]) .. function:: create_test_db([verbosity=1, autoclobber=False])
Creates a new test database and runs ``syncdb`` against it. Creates a new test database and runs ``migrate`` against it.
``verbosity`` has the same behavior as in ``run_tests()``. ``verbosity`` has the same behavior as in ``run_tests()``.

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@ -1215,9 +1215,9 @@ documentation<dumpdata>` for more details.
.. note:: .. note::
If you've ever run :djadmin:`manage.py syncdb<syncdb>`, you've If you've ever run :djadmin:`manage.py migrate<migrate>`, you've
already used a fixture without even knowing it! When you call already used a fixture without even knowing it! When you call
:djadmin:`syncdb` in the database for the first time, Django :djadmin:`migrate` in the database for the first time, Django
installs a fixture called ``initial_data``. This gives you a way installs a fixture called ``initial_data``. This gives you a way
of populating a new database with any initial data, such as a of populating a new database with any initial data, such as a
default set of categories. default set of categories.