256 lines
11 KiB
Python
256 lines
11 KiB
Python
import codecs
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import copy
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from decimal import Decimal
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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, (Decimal, float)):
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return str(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).replace("\'", "\'\'")
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elif value is None:
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return "NULL"
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elif isinstance(value, (bytes, bytearray, six.memoryview)):
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# Bytes are only allowed for BLOB fields, encoded as string
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# literals containing hexadecimal data and preceded by a single "X"
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# character:
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# value = b'\x01\x02' => value_hex = b'0102' => return X'0102'
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value = bytes(value)
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hex_encoder = codecs.getencoder('hex_codec')
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value_hex, _length = hex_encoder(value)
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# Use 'ascii' encoding for b'01' => '01', no need to use force_text here.
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return "X'%s'" % value_hex.decode('ascii')
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else:
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raise ValueError("Cannot quote parameter value %r of type %s" % (value, type(value)))
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def _remake_table(self, model, create_fields=[], delete_fields=[], alter_fields=[], override_uniques=None,
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override_indexes=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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# Since mapping might mix column names and default values,
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# its values must be already quoted.
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mapping = dict((f.column, self.quote_name(f.column)) for f in model._meta.local_fields)
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# This maps field names (not columns) for things like unique_together
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rename_mapping = {}
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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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self.effective_default(field)
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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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body.pop(old_field.name, None)
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mapping.pop(old_field.column, None)
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body[new_field.name] = new_field
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if old_field.null and not new_field.null:
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case_sql = "coalesce(%(col)s, %(default)s)" % {
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'col': self.quote_name(old_field.column),
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'default': self.quote_value(self.effective_default(new_field))
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}
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mapping[new_field.column] = case_sql
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else:
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mapping[new_field.column] = self.quote_name(old_field.column)
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rename_mapping[old_field.name] = new_field.name
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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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# Provide isolated instances of the fields to the new model body
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# Instantiating the new model with an alternate db_table will alter
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# the internal references of some of the provided fields.
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body = copy.deepcopy(body)
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# Work out the new value of unique_together, taking renames into
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# account
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if override_uniques is None:
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override_uniques = [
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[rename_mapping.get(n, n) for n in unique]
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for unique in model._meta.unique_together
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]
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# Work out the new value for index_together, taking renames into
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# account
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if override_indexes is None:
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override_indexes = [
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[rename_mapping.get(n, n) for n in index]
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for index in model._meta.index_together
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]
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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': override_uniques,
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'index_together': override_indexes,
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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. We remove things from the
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# deferred SQL that match our table name, too
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self.deferred_sql = [x for x in self.deferred_sql if model._meta.db_table not in x]
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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(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
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self.delete_model(model, handle_autom2m=False)
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# Rename the new to the old
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self.alter_db_table(temp_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 delete_model(self, model, handle_autom2m=True):
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if handle_autom2m:
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super(DatabaseSchemaEditor, self).delete_model(model)
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else:
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# Delete the table (and only that)
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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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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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# It might not actually have a column behind it
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if field.db_parameters(connection=self.connection)['type'] is None:
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return
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self._remake_table(model, delete_fields=[field])
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def _alter_field(self, model, old_field, new_field, old_type, new_type,
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old_db_params, new_db_params, strict=False):
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"""Actually perform a "physical" (non-ManyToMany) field update."""
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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_index_together(self, model, old_index_together, new_index_together):
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"""
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Deals with a model changing its index_together.
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Note: The input index_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_indexes=new_index_together)
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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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# The field name didn't change, but some options did; we have to propagate this altering.
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self._remake_table(
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old_field.rel.through,
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alter_fields=[(
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# We need the field that points to the target model, so we can tell alter_field to change it -
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# this is m2m_reverse_field_name() (as opposed to m2m_field_name, which points to our model)
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old_field.rel.through._meta.get_field_by_name(old_field.m2m_reverse_field_name())[0],
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new_field.rel.through._meta.get_field_by_name(new_field.m2m_reverse_field_name())[0],
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)],
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override_uniques=(new_field.m2m_field_name(), new_field.m2m_reverse_field_name()),
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)
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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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