Stylistic fixes: triple-quoted docstrings, more comments
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@ -59,21 +59,27 @@ class BaseDatabaseSchemaEditor(object):
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# State-managing methods
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def start(self):
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"Marks the start of a schema-altering run"
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"""
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Marks the start of a schema-altering run.
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"""
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self.deferred_sql = []
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self.connection.commit_unless_managed()
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self.connection.enter_transaction_management()
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self.connection.managed(True)
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def commit(self):
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"Finishes a schema-altering run"
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"""
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Finishes a schema-altering run.
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"""
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for sql in self.deferred_sql:
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self.execute(sql)
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self.connection.commit()
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self.connection.leave_transaction_management()
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def rollback(self):
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"Tries to roll back a schema-altering run. Call instead of commit()"
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"""
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Tries to roll back a schema-altering run. Call instead of commit().
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"""
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if not self.connection.features.can_rollback_ddl:
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raise RuntimeError("Cannot rollback schema changes on this backend")
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self.connection.rollback()
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@ -137,7 +143,9 @@ class BaseDatabaseSchemaEditor(object):
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return sql, params
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def effective_default(self, field):
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"Returns a field's effective database default value"
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"""
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Returns a field's effective database default value
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"""
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if field.has_default():
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default = field.get_default()
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elif not field.null and field.blank and field.empty_strings_allowed:
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@ -580,7 +588,9 @@ class BaseDatabaseSchemaEditor(object):
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)
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def _alter_many_to_many(self, model, old_field, new_field, strict):
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"Alters M2Ms to repoint their to= endpoints."
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"""
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Alters M2Ms to repoint their to= endpoints.
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"""
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# Rename the through table
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self.alter_db_table(old_field.rel.through, old_field.rel.through._meta.db_table, new_field.rel.through._meta.db_table)
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# Repoint the FK to the other side
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@ -591,7 +601,9 @@ class BaseDatabaseSchemaEditor(object):
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)
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def _create_index_name(self, model, column_names, suffix=""):
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"Generates a unique name for an index/unique constraint."
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"""
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Generates a unique name for an index/unique constraint.
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"""
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# If there is just one column in the index, use a default algorithm from Django
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if len(column_names) == 1 and not suffix:
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return truncate_name(
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@ -609,7 +621,9 @@ class BaseDatabaseSchemaEditor(object):
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return index_name
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def _constraint_names(self, model, column_names=None, unique=None, primary_key=None, index=None, foreign_key=None, check=None):
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"Returns all constraint names matching the columns and conditions"
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"""
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Returns all constraint names matching the columns and conditions
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"""
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column_names = set(column_names) if column_names else None
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constraints = self.connection.introspection.get_constraints(self.connection.cursor(), model._meta.db_table)
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result = []
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@ -207,10 +207,13 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
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# Get the PK
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pk_column = self.get_primary_key_column(cursor, table_name)
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if pk_column:
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# SQLite doesn't actually give a name to the PK constraint,
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# so we invent one. This is fine, as the SQLite backend never
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# deletes PK constraints by name.
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constraints["__primary__"] = {
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"columns": set([pk_column]),
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"primary_key": True,
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"unique": False, # It's not actually a unique constraint
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"unique": False, # It's not actually a unique constraint.
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"foreign_key": False,
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"check": False,
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"index": False,
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@ -8,7 +8,9 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
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sql_delete_table = "DROP TABLE %(table)s"
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def _remake_table(self, model, create_fields=[], delete_fields=[], alter_fields=[], rename_fields=[], override_uniques=None):
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"Shortcut to transform a model from old_model into new_model"
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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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@ -98,7 +100,13 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
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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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# Ensure this field is even column-based
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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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@ -114,10 +122,17 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
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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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"Alters M2Ms to repoint their to= endpoints."
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"""
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Alters M2Ms to repoint their to= endpoints.
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"""
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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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