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113 lines
2.2 KiB
Plaintext
113 lines
2.2 KiB
Plaintext
============
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SchemaEditor
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============
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Django's migration system is split into two parts; the logic for calculating
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and storing what operations should be run (``django.db.migrations``), and the
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database abstraction layer that turns things like "create a model" or
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"delete a field" into SQL - which is the job of the ``SchemaEditor``.
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It's unlikely that you will want to interact directly with ``SchemaEditor`` as
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a normal developer using Django, but if you want to write your own migration
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system, or have more advanced needs, it's a lot nicer than writing SQL.
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Each database backend in Django supplies its own version of ``SchemaEditor``,
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and it's always accessible via the ``connection.schema_editor()`` context
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manager::
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with connection.schema_editor() as schema_editor:
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schema_editor.delete_model(MyModel)
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It must be used via the context manager as this allows it to manage things
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like transactions and deferred SQL (like creating ``ForeignKey`` constraints).
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It exposes all possible operations as methods, that should be called in
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the order you wish changes to be applied. Some possible operations or types
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of change are not possible on all databases - for example, MyISAM does not
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support foreign key constraints.
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Methods
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=======
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execute
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-------
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::
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execute(sql, params=[])
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Executes the SQL statement passed in, with parameters if supplied. This
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is a simple wrapper around the normal database cursors that allows
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capture of the SQL to a ``.sql`` file if the user wishes.
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create_model
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------------
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::
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create_model(model)
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delete_model
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------------
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::
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delete_model(model)
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alter_unique_together
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---------------------
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::
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alter_unique_together(model, old_unique_together, new_unique_together)
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alter_index_together
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--------------------
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::
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alter_index_together(model, old_index_together, new_index_together)
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alter_db_table
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--------------
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::
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alter_db_table(model, old_db_table, new_db_table)
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alter_db_tablespace
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-------------------
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::
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alter_db_tablespace(model, old_db_tablespace, new_db_tablespace)
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add_field
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---------
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::
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add_field(model, field)
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remove_field
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------------
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::
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remove_field(model, field)
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alter_field
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------------
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::
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alter_field(model, old_field, new_field, strict=False)
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