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75 lines
3 KiB
Text
75 lines
3 KiB
Text
===========
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Tablespaces
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===========
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A common paradigm for optimizing performance in database systems is the use of
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`tablespaces`_ to organize disk layout.
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.. _`tablespaces`: https://en.wikipedia.org/wiki/Tablespace
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.. warning::
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Django does not create the tablespaces for you. Please refer to your
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database engine's documentation for details on creating and managing
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tablespaces.
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Declaring tablespaces for tables
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================================
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A tablespace can be specified for the table generated by a model by supplying
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the :attr:`~django.db.models.Options.db_tablespace` option inside the model's
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``class Meta``. This option also affects tables automatically created for
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:class:`~django.db.models.ManyToManyField`\ s in the model.
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You can use the :setting:`DEFAULT_TABLESPACE` setting to specify a default value
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for :attr:`~django.db.models.Options.db_tablespace`. This is useful for setting
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a tablespace for the built-in Django apps and other applications whose code you
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cannot control.
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Declaring tablespaces for indexes
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=================================
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You can pass the :attr:`~django.db.models.Index.db_tablespace` option to an
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``Index`` constructor to specify the name of a tablespace to use for the index.
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For single field indexes, you can pass the
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:attr:`~django.db.models.Field.db_tablespace` option to a ``Field`` constructor
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to specify an alternate tablespace for the field's column index. If the column
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doesn't have an index, the option is ignored.
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You can use the :setting:`DEFAULT_INDEX_TABLESPACE` setting to specify
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a default value for :attr:`~django.db.models.Field.db_tablespace`.
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If :attr:`~django.db.models.Field.db_tablespace` isn't specified and you didn't
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set :setting:`DEFAULT_INDEX_TABLESPACE`, the index is created in the same
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tablespace as the tables.
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An example
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==========
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.. code-block:: python
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class TablespaceExample(models.Model):
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name = models.CharField(max_length=30, db_index=True, db_tablespace="indexes")
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data = models.CharField(max_length=255, db_index=True)
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shortcut = models.CharField(max_length=7)
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edges = models.ManyToManyField(to="self", db_tablespace="indexes")
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class Meta:
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db_tablespace = "tables"
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indexes = [models.Index(fields=['shortcut'], db_tablespace='other_indexes')]
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In this example, the tables generated by the ``TablespaceExample`` model (i.e.
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the model table and the many-to-many table) would be stored in the ``tables``
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tablespace. The index for the name field and the indexes on the many-to-many
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table would be stored in the ``indexes`` tablespace. The ``data`` field would
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also generate an index, but no tablespace for it is specified, so it would be
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stored in the model tablespace ``tables`` by default. The index for the
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``shortcut`` field would be stored in the ``other_indexes`` tablespace.
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Database support
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================
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PostgreSQL and Oracle support tablespaces. SQLite and MySQL don't.
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When you use a backend that lacks support for tablespaces, Django ignores all
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tablespace-related options.
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