mirror of
https://github.com/django/django.git
synced 2024-11-29 22:56:46 +01:00
Fixed #5627: Added documentation and caveats about using the oracle
backend. git-svn-id: http://code.djangoproject.com/svn/django/trunk@6432 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Ian Kelly
parent
4b4ecb6d66
commit
e70ecc93ff
@ -163,3 +163,118 @@ storage engine, you have a couple of options.
|
||||
|
||||
.. _AlterModelOnSyncDB: http://code.djangoproject.com/wiki/AlterModelOnSyncDB
|
||||
|
||||
|
||||
Oracle Notes
|
||||
============
|
||||
|
||||
Django supports `Oracle Database Server`_ versions 9i and higher. Oracle
|
||||
version 10g or later is required to use Django's ``regex`` and ``iregex`` query
|
||||
operators. You will also need the `cx_Oracle`_ driver, version 4.3.1 or newer.
|
||||
|
||||
.. _`Oracle Database Server`: http://www.oracle.com/
|
||||
.. _`cx_Oracle`: http://cx-oracle.sourceforge.net/
|
||||
|
||||
To run ``python manage.py syncdb``, you'll need to create an Oracle database
|
||||
user with CREATE TABLE, CREATE SEQUENCE, and CREATE PROCEDURE privileges. To
|
||||
run Django's test suite, the user also needs CREATE and DROP DATABASE and
|
||||
CREATE and DROP TABLESPACE privileges.
|
||||
|
||||
Connecting to the Database
|
||||
--------------------------
|
||||
|
||||
Your Django settings.py file should look something like this for Oracle::
|
||||
|
||||
DATABASE_ENGINE = 'oracle'
|
||||
DATABASE_NAME = 'xe'
|
||||
DATABASE_USER = 'a_user'
|
||||
DATABASE_PASSWORD = 'a_password'
|
||||
DATABASE_HOST = ''
|
||||
DATABASE_PORT = ''
|
||||
|
||||
If you don't use a ``tnsnames.ora`` file or a similar naming method that
|
||||
recognizes the SID ("xe" in this example), then fill in both ``DATABASE_HOST``
|
||||
and ``DATABASE_PORT`` like so::
|
||||
|
||||
DATABASE_ENGINE = 'oracle'
|
||||
DATABASE_NAME = 'xe'
|
||||
DATABASE_USER = 'a_user'
|
||||
DATABASE_PASSWORD = 'a_password'
|
||||
DATABASE_HOST = 'dbprod01ned.mycompany.com'
|
||||
DATABASE_PORT = '1540'
|
||||
|
||||
You should supply both ``DATABASE_HOST`` and ``DATABASE_PORT``, or leave both
|
||||
as empty strings.
|
||||
|
||||
Tablespace Options
|
||||
------------------
|
||||
|
||||
A common paradigm for optimizing performance in Oracle-based systems is the
|
||||
use of `tablespaces`_ to organize disk layout. The Oracle backend supports
|
||||
this use case by adding ``db_tablespace`` options to the ``Meta`` and
|
||||
``Field`` classes. (When using a backend that lacks support for tablespaces,
|
||||
these options are ignored.)
|
||||
|
||||
.. _`tablespaces`: http://en.wikipedia.org/wiki/Tablespace
|
||||
|
||||
A tablespace can be specified for the table(s) generated by a model by
|
||||
supplying the ``db_tablespace`` option inside the model's ``Meta`` class.
|
||||
Additionally, the ``db_tablespace`` option can be passed to a ``Field``
|
||||
constructor to specify an alternate tablespace for the ``Field``'s column
|
||||
index. If no index would be created for the column, the ``db_tablespace``
|
||||
option is ignored.
|
||||
|
||||
::
|
||||
|
||||
class TablespaceExample(models.Model):
|
||||
name = models.CharField(maxlength=30, db_index=True, db_tablespace="indexes")
|
||||
data = models.CharField(maxlength=255, db_index=True)
|
||||
edges = models.ManyToManyField(to="self", db_tablespace="indexes")
|
||||
|
||||
class Meta:
|
||||
db_tablespace = "tables"
|
||||
|
||||
In this example, the tables generated by the ``TablespaceExample`` model
|
||||
(i.e., the model table and the many-to-many table) would be stored in the
|
||||
``tables`` tablespace. The index for the name field and the indexes on the
|
||||
many-to-many table would be stored in the ``indexes`` tablespace. The ``data``
|
||||
field would also generate an index, but no tablespace for it is specified, so
|
||||
it would be stored in the model tablespace ``tables`` by default.
|
||||
|
||||
Django does not create the tablespaces for you. Please refer to `Oracle's
|
||||
documentation`_ for details on creating and managing tablespaces.
|
||||
|
||||
.. _`Oracle's documentation`: http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_7003.htm#SQLRF01403
|
||||
|
||||
Naming Issues
|
||||
-------------
|
||||
|
||||
Oracle imposes a name length limit of 30 characters. To accommodate this, the
|
||||
backend truncates database identifiers to fit, replacing the final four
|
||||
characters of the truncated name with a repeatable MD5 hash value.
|
||||
|
||||
NULL and Empty Strings
|
||||
----------------------
|
||||
|
||||
Django generally prefers to use the empty string ('') rather than NULL, but
|
||||
Oracle treats both identically. To get around this, the Oracle backend
|
||||
coerces the ``null=True`` option on fields that permit the empty string as a
|
||||
value. When fetching from the database, it is assumed that a NULL value in
|
||||
one of these fields really means the empty string, and the data is silently
|
||||
converted to reflect this assumption.
|
||||
|
||||
TextField Limitations
|
||||
---------------------
|
||||
|
||||
The Oracle backend stores ``TextFields`` as ``NCLOB`` columns. Oracle imposes
|
||||
some limitations on the usage of such LOB columns in general:
|
||||
|
||||
* LOB columns may not be used as primary keys.
|
||||
|
||||
* LOB columns may not be used in indexes.
|
||||
|
||||
* LOB columns may not be used in a ``SELECT DISTINCT`` list. This means that
|
||||
attempting to use the ``QuerySet.distinct`` method on a model that
|
||||
includes ``TextField`` columns will result in an error when run against
|
||||
Oracle. A workaround to this is to keep ``TextField`` columns out of any
|
||||
models that you foresee performing ``.distinct`` queries on, and to
|
||||
include the ``TextField`` in a related model instead.
|
||||
|
||||
Loading…
Reference in New Issue
Block a user