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Edited docs/databases.txt Oracle changes from [6432] 

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Adrian Holovaty 2007-11-30 05:03:32 +00:00
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@ -172,22 +172,32 @@ storage engine, you have a couple of options.
.. _AlterModelOnSyncDB: http://code.djangoproject.com/wiki/AlterModelOnSyncDB .. _AlterModelOnSyncDB: http://code.djangoproject.com/wiki/AlterModelOnSyncDB
Oracle Notes Oracle notes
============ ============
Django supports `Oracle Database Server`_ versions 9i and higher. Oracle Django supports `Oracle Database Server`_ versions 9i and higher. Oracle
version 10g or later is required to use Django's ``regex`` and ``iregex`` query 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. operators. You will also need the `cx_Oracle`_ driver, version 4.3.1 or newer.
.. _`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/
To run ``python manage.py syncdb``, you'll need to create an Oracle database In order for the ``python manage.py syncdb`` command to work, your Oracle
user with CREATE TABLE, CREATE SEQUENCE, CREATE PROCEDURE, and CREATE TRIGGER database user must have privileges to run the following commands:
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 * CREATE TABLE
* CREATE SEQUENCE
* CREATE PROCEDURE
* CREATE TRIGGER
To run Django's test suite, the user needs these *additional* privileges:
* CREATE DATABASE
* DROP DATABASE
* CREATE TABLESPACE
* DROP TABLESPACE
Connecting to the database
-------------------------- --------------------------
Your Django settings.py file should look something like this for Oracle:: Your Django settings.py file should look something like this for Oracle::
@ -213,29 +223,29 @@ and ``DATABASE_PORT`` like so::
You should supply both ``DATABASE_HOST`` and ``DATABASE_PORT``, or leave both You should supply both ``DATABASE_HOST`` and ``DATABASE_PORT``, or leave both
as empty strings. as empty strings.
Tablespace Options Tablespace options
------------------ ------------------
A common paradigm for optimizing performance in Oracle-based systems is the A common paradigm for optimizing performance in Oracle-based systems is the
use of `tablespaces`_ to organize disk layout. The Oracle backend supports use of `tablespaces`_ to organize disk layout. The Oracle backend supports
this use case by adding ``db_tablespace`` options to the ``Meta`` and this use case by adding ``db_tablespace`` options to the ``Meta`` and
``Field`` classes. (When using a backend that lacks support for tablespaces, ``Field`` classes. (When you use a backend that lacks support for tablespaces,
these options are ignored.) Django ignores these options.)
.. _`tablespaces`: http://en.wikipedia.org/wiki/Tablespace .. _`tablespaces`: http://en.wikipedia.org/wiki/Tablespace
A tablespace can be specified for the table(s) generated by a model by 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. supplying the ``db_tablespace`` option inside the model's ``class Meta``.
Additionally, the ``db_tablespace`` option can be passed to a ``Field`` Additionally, you can pass the ``db_tablespace`` option to a ``Field``
constructor to specify an alternate tablespace for the ``Field``'s column constructor to specify an alternate tablespace for the ``Field``'s column
index. If no index would be created for the column, the ``db_tablespace`` index. If no index would be created for the column, the ``db_tablespace``
option is ignored. option is ignored.
:: ::
class TablespaceExample(models.Model): class TablespaceExample(models.Model):
name = models.CharField(maxlength=30, db_index=True, db_tablespace="indexes") name = models.CharField(max_length=30, db_index=True, db_tablespace="indexes")
data = models.CharField(maxlength=255, db_index=True) data = models.CharField(max_length=255, db_index=True)
edges = models.ManyToManyField(to="self", db_tablespace="indexes") edges = models.ManyToManyField(to="self", db_tablespace="indexes")
class Meta: class Meta:
@ -243,46 +253,46 @@ option is ignored.
In this example, the tables generated by the ``TablespaceExample`` model 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 (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 ``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`` 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 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. it would be stored in the model tablespace ``tables`` by default.
Django does not create the tablespaces for you. Please refer to `Oracle's Django does not create the tablespaces for you. Please refer to `Oracle's
documentation`_ for details on creating and managing tablespaces. 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 .. _`Oracle's documentation`: http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_7003.htm#SQLRF01403
Naming Issues Naming issues
------------- -------------
Oracle imposes a name length limit of 30 characters. To accommodate this, the 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.
NULL and Empty Strings NULL and empty strings
---------------------- ----------------------
Django generally prefers to use the empty string ('') rather than NULL, but Django generally prefers to use the empty string ('') rather than NULL, but
Oracle treats both identically. To get around this, the Oracle backend 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 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 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 one of these fields really means the empty string, and the data is silently
converted to reflect this assumption. converted to reflect this assumption.
TextField Limitations ``TextField`` limitations
--------------------- -------------------------
The Oracle backend stores ``TextFields`` as ``NCLOB`` columns. Oracle imposes The Oracle backend stores ``TextFields`` as ``NCLOB`` columns. Oracle imposes
some limitations on the usage of such LOB columns in general: 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 as primary keys.
* LOB columns may not be used in indexes. * LOB columns may not be used in indexes.
* LOB columns may not be used in a ``SELECT DISTINCT`` list. This means that * 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 attempting to use the ``QuerySet.distinct`` method on a model that
includes ``TextField`` columns will result in an error when run against includes ``TextField`` columns will result in an error when run against
Oracle. A workaround to this is to keep ``TextField`` columns out of any Oracle. A workaround to this is to keep ``TextField`` columns out of any
models that you foresee performing ``.distinct`` queries on, and to models that you foresee performing ``distinct()`` queries on, and to
include the ``TextField`` in a related model instead. include the ``TextField`` in a related model instead.