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00e3b9a2a9
Changed the migration autodetector to remove models last so that FK and M2M fields will not be left as dangling references. Added a check in the migration state renderer to error out in the presence of dangling references instead of leaving them as strings. Fixed a bug in the sqlite backend to handle the deletion of M2M fields with "through" models properly (i.e., do nothing successfully). Thanks to melinath for report, loic for tests and andrewgodwin and charettes for assistance with architecture.
189 lines
8.2 KiB
Python
189 lines
8.2 KiB
Python
from django.utils import six
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from django.apps.registry import Apps
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from django.db.backends.schema import BaseDatabaseSchemaEditor
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from django.db.models.fields.related import ManyToManyField
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class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
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sql_delete_table = "DROP TABLE %(table)s"
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sql_create_inline_fk = "REFERENCES %(to_table)s (%(to_column)s)"
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def quote_value(self, value):
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# Inner import to allow nice failure for backend if not present
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import _sqlite3
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try:
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value = _sqlite3.adapt(value)
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except _sqlite3.ProgrammingError:
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pass
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# Manual emulation of SQLite parameter quoting
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if isinstance(value, type(True)):
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return str(int(value))
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elif isinstance(value, six.integer_types):
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return str(value)
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elif isinstance(value, six.string_types):
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return '"%s"' % six.text_type(value)
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elif value is None:
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return "NULL"
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else:
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raise ValueError("Cannot quote parameter value %r" % value)
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def _remake_table(self, model, create_fields=[], delete_fields=[], alter_fields=[], rename_fields=[], override_uniques=None):
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"""
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Shortcut to transform a model from old_model into new_model
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"""
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# Work out the new fields dict / mapping
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body = dict((f.name, f) for f in model._meta.local_fields)
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mapping = dict((f.column, f.column) for f in model._meta.local_fields)
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# If any of the new or altered fields is introducing a new PK,
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# remove the old one
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restore_pk_field = None
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if any(f.primary_key for f in create_fields) or any(n.primary_key for o, n in alter_fields):
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for name, field in list(body.items()):
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if field.primary_key:
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field.primary_key = False
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restore_pk_field = field
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if field.auto_created:
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del body[name]
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del mapping[field.column]
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# Add in any created fields
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for field in create_fields:
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body[field.name] = field
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# If there's a default, insert it into the copy map
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if field.has_default():
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mapping[field.column] = self.quote_value(
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field.get_default()
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)
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# Add in any altered fields
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for (old_field, new_field) in alter_fields:
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del body[old_field.name]
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del mapping[old_field.column]
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body[new_field.name] = new_field
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mapping[new_field.column] = old_field.column
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# Remove any deleted fields
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for field in delete_fields:
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del body[field.name]
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del mapping[field.column]
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# Remove any implicit M2M tables
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if isinstance(field, ManyToManyField) and field.rel.through._meta.auto_created:
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return self.delete_model(field.rel.through)
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# Work inside a new app registry
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apps = Apps()
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# Construct a new model for the new state
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meta_contents = {
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'app_label': model._meta.app_label,
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'db_table': model._meta.db_table + "__new",
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'unique_together': model._meta.unique_together if override_uniques is None else override_uniques,
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'apps': apps,
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}
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meta = type("Meta", tuple(), meta_contents)
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body['Meta'] = meta
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body['__module__'] = model.__module__
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temp_model = type(model._meta.object_name, model.__bases__, body)
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# Create a new table with that format
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self.create_model(temp_model)
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# Copy data from the old table
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field_maps = list(mapping.items())
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self.execute("INSERT INTO %s (%s) SELECT %s FROM %s" % (
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self.quote_name(temp_model._meta.db_table),
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', '.join(self.quote_name(x) for x, y in field_maps),
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', '.join(self.quote_name(y) for x, y in field_maps),
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self.quote_name(model._meta.db_table),
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))
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# Delete the old table (not using self.delete_model to avoid deleting
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# all implicit M2M tables)
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self.execute(self.sql_delete_table % {
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"table": self.quote_name(model._meta.db_table),
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})
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# Rename the new to the old
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self.alter_db_table(model, temp_model._meta.db_table, model._meta.db_table)
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# Run deferred SQL on correct table
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for sql in self.deferred_sql:
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self.execute(sql.replace(temp_model._meta.db_table, model._meta.db_table))
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self.deferred_sql = []
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# Fix any PK-removed field
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if restore_pk_field:
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restore_pk_field.primary_key = True
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def add_field(self, model, field):
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"""
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Creates a field on a model.
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Usually involves adding a column, but may involve adding a
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table instead (for M2M fields)
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"""
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# Special-case implicit M2M tables
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if isinstance(field, ManyToManyField) and field.rel.through._meta.auto_created:
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return self.create_model(field.rel.through)
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self._remake_table(model, create_fields=[field])
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def remove_field(self, model, field):
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"""
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Removes a field from a model. Usually involves deleting a column,
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but for M2Ms may involve deleting a table.
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"""
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# M2M fields are a special case
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if isinstance(field, ManyToManyField):
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# For implicit M2M tables, delete the auto-created table
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if field.rel.through._meta.auto_created:
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self.delete_model(field.rel.through)
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# For explicit "through" M2M fields, do nothing
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# For everything else, remake.
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else:
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self._remake_table(model, delete_fields=[field])
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def alter_field(self, model, old_field, new_field, strict=False):
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"""
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Allows a field's type, uniqueness, nullability, default, column,
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constraints etc. to be modified.
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Requires a copy of the old field as well so we can only perform
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changes that are required.
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If strict is true, raises errors if the old column does not match old_field precisely.
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"""
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old_db_params = old_field.db_parameters(connection=self.connection)
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old_type = old_db_params['type']
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new_db_params = new_field.db_parameters(connection=self.connection)
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new_type = new_db_params['type']
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if old_type is None and new_type is None and (old_field.rel.through and new_field.rel.through and old_field.rel.through._meta.auto_created and new_field.rel.through._meta.auto_created):
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return self._alter_many_to_many(model, old_field, new_field, strict)
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elif old_type is None or new_type is None:
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raise ValueError("Cannot alter field %s into %s - they are not compatible types (probably means only one is an M2M with implicit through model)" % (
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old_field,
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new_field,
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))
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# Alter by remaking table
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self._remake_table(model, alter_fields=[(old_field, new_field)])
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def alter_unique_together(self, model, old_unique_together, new_unique_together):
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"""
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Deals with a model changing its unique_together.
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Note: The input unique_togethers must be doubly-nested, not the single-
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nested ["foo", "bar"] format.
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"""
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self._remake_table(model, override_uniques=new_unique_together)
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def _alter_many_to_many(self, model, old_field, new_field, strict):
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"""
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Alters M2Ms to repoint their to= endpoints.
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"""
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if old_field.rel.through._meta.db_table == new_field.rel.through._meta.db_table:
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return
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# Make a new through table
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self.create_model(new_field.rel.through)
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# Copy the data across
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self.execute("INSERT INTO %s (%s) SELECT %s FROM %s" % (
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self.quote_name(new_field.rel.through._meta.db_table),
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', '.join([
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"id",
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new_field.m2m_column_name(),
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new_field.m2m_reverse_name(),
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]),
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', '.join([
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"id",
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old_field.m2m_column_name(),
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old_field.m2m_reverse_name(),
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]),
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self.quote_name(old_field.rel.through._meta.db_table),
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))
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# Delete the old through table
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self.delete_model(old_field.rel.through)
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