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| author | Liz Lemon <lizlemon@gmail.com> | 2016-08-02 19:55:57 -0400 |
|---|---|---|
| committer | Tim Graham <timograham@gmail.com> | 2016-08-05 12:55:32 -0400 |
| commit | ea65c7cb4819cf18ac66215bc7b4df4af3fbe5ad (patch) | |
| tree | e43c4b884e97c23ad7dd41eb5d32b7ddec508645 /docs | |
| parent | e139ef5741716d8cb715ff17da2b33df08d85309 (diff) | |
Edited multi-db topic guide for grammar and clarity.
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/topics/db/multi-db.txt | 33 |
1 files changed, 24 insertions, 9 deletions
diff --git a/docs/topics/db/multi-db.txt b/docs/topics/db/multi-db.txt index e8d362fff7..b685d3c53e 100644 --- a/docs/topics/db/multi-db.txt +++ b/docs/topics/db/multi-db.txt @@ -45,11 +45,11 @@ If the concept of a ``default`` database doesn't make sense in the context of your project, you need to be careful to always specify the database that you want to use. Django requires that a ``default`` database entry be defined, but the parameters dictionary can be left blank if it will not be -used. You must setup :setting:`DATABASE_ROUTERS` for all of your apps' models, -including those in any contrib and third-party apps you are using, so that no -queries are routed to the default database in order to do this. The following -is an example ``settings.py`` snippet defining two non-default databases, with -the ``default`` entry intentionally left empty:: +used. To do this, you must set up :setting:`DATABASE_ROUTERS` for all of your +apps' models, including those in any contrib and third-party apps you're using, +so that no queries are routed to the default database. The following is an +example ``settings.py`` snippet defining two non-default databases, with the +``default`` entry intentionally left empty:: DATABASES = { 'default': {}, @@ -78,7 +78,7 @@ The :djadmin:`migrate` management command operates on one database at a time. By default, it operates on the ``default`` database, but by providing the :option:`--database <migrate --database>` option, you can tell it to synchronize a different database. So, to synchronize all models onto -all databases in our example, you would need to call:: +all databases in the first example above, you would need to call:: $ ./manage.py migrate $ ./manage.py migrate --database=users @@ -88,6 +88,13 @@ particular database, you can define a :ref:`database router<topics-db-multi-db-routing>` that implements a policy constraining the availability of particular models. +If, as in the second example above, you've left the ``default`` database empty, +you must provide a database name each time you run :djadmin:`migrate`. Omitting +the database name would raise an error. For the second example:: + + $ ./manage.py migrate --database=users + $ ./manage.py migrate --database=customers + Using other management commands ------------------------------- @@ -359,8 +366,8 @@ routers are defined):: DATABASE_ROUTERS = ['path.to.AuthRouter', 'path.to.PrimaryReplicaRouter'] The order in which routers are processed is significant. Routers will -be queried in the order the are listed in the -:setting:`DATABASE_ROUTERS` setting . In this example, the +be queried in the order they are listed in the +:setting:`DATABASE_ROUTERS` setting. In this example, the ``AuthRouter`` is processed before the ``PrimaryReplicaRouter``, and as a result, decisions concerning the models in ``auth`` are processed before any other decision is made. If the :setting:`DATABASE_ROUTERS` @@ -394,6 +401,13 @@ With this setup installed, lets run some Django code:: >>> # ... but if we re-retrieve the object, it will come back on a replica >>> mh = Book.objects.get(title='Mostly Harmless') +This example defined a router to handle interaction with models from the +``auth`` app, and other routers to handle interaction with all other apps. If +you left your ``default`` database empty and don't want to define a catch-all +database router to handle all apps not otherwise specified, your routers must +handle the names of all apps in :setting:`INSTALLED_APPS` before you migrate. +See :ref:`contrib_app_multiple_databases` for information about contrib apps +that must be together in one database. Manually selecting a database ============================= @@ -586,7 +600,8 @@ where all objects of a given type are stored on a specific database usage of multiple databases is more complex, your ``ModelAdmin`` will need to reflect that strategy. -Inlines can be handled in a similar fashion. They require three customized methods:: +:class:`~django.contrib.admin.InlineModelAdmin` objects can be handled in a +similar fashion. They require three customized methods:: class MultiDBTabularInline(admin.TabularInline): using = 'other' |
