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authorLiz Lemon <lizlemon@gmail.com>2016-08-02 19:55:57 -0400
committerTim Graham <timograham@gmail.com>2016-08-05 12:55:32 -0400
commitea65c7cb4819cf18ac66215bc7b4df4af3fbe5ad (patch)
treee43c4b884e97c23ad7dd41eb5d32b7ddec508645 /docs
parente139ef5741716d8cb715ff17da2b33df08d85309 (diff)
Edited multi-db topic guide for grammar and clarity.
Diffstat (limited to 'docs')
-rw-r--r--docs/topics/db/multi-db.txt33
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'