97 lines
3.4 KiB
Plaintext
97 lines
3.4 KiB
Plaintext
=========================================
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Integrating Django with a legacy database
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=========================================
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While Django is best suited for developing new applications, it's quite
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possible to integrate it into legacy databases. Django includes a couple of
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utilities to automate as much of this process as possible.
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This document assumes you know the Django basics, as covered in the
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:doc:`tutorial </intro/tutorial01>`.
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Once you've got Django set up, you'll follow this general process to integrate
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with an existing database.
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Give Django your database parameters
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====================================
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You'll need to tell Django what your database connection parameters are, and
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what the name of the database is. Do that by editing the :setting:`DATABASES`
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setting and assigning values to the following keys for the ``'default'``
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connection:
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* :setting:`NAME`
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* :setting:`ENGINE <DATABASE-ENGINE>`
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* :setting:`USER`
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* :setting:`PASSWORD`
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* :setting:`HOST`
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* :setting:`PORT`
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Auto-generate the models
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========================
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.. highlight:: bash
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Django comes with a utility called :djadmin:`inspectdb` that can create models
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by introspecting an existing database. You can view the output by running this
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command::
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$ python manage.py inspectdb
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Save this as a file by using standard Unix output redirection::
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$ python manage.py inspectdb > models.py
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This feature is meant as a shortcut, not as definitive model generation. See the
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:djadmin:`documentation of inspectdb <inspectdb>` for more information.
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Once you've cleaned up your models, name the file ``models.py`` and put it in
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the Python package that holds your app. Then add the app to your
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:setting:`INSTALLED_APPS` setting.
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If your plan is that your Django application(s) modify data (i.e. edit, remove
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records and create new ones) in the existing database tables corresponding to
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any of the introspected models then one of the manual review and edit steps
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you need to perform on the resulting ``models.py`` file is to change the
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Python declaration of each one of these models to specify it is a
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:attr:`managed <django.db.models.Options.managed>` one. For example, consider
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this generated model definition:
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.. code-block:: python
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:emphasize-lines: 5
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class Person(models.Model):
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id = models.IntegerField(primary_key=True)
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first_name = models.CharField(max_length=70)
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class Meta:
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managed = False
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db_table = 'CENSUS_PERSONS'
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If you wanted to modify existing data on your ``CENSUS_PERSONS`` SQL table
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with Django you'd need to change the ``managed`` option highlighted above to
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``True`` (or simply remove it to let it because ``True`` is its default value).
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This serves as an explicit opt-in to give your nascent Django project write
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access to your precious data on a model by model basis.
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.. versionchanged:: 1.6
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The behavior by which introspected models are created as unmanaged ones is new
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in Django 1.6.
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Install the core Django tables
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==============================
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Next, run the :djadmin:`migrate` command to install any extra needed database
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records such as admin permissions and content types::
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$ python manage.py migrate
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Test and tweak
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==============
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Those are the basic steps -- from here you'll want to tweak the models Django
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generated until they work the way you'd like. Try accessing your data via the
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Django database API, and try editing objects via Django's admin site, and edit
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the models file accordingly.
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