def add_column(
self,
table_class_name: str,
tablename: str,
column_name: str,
column_class_name: str = "",
column_class: t.Optional[t.Type[Column]] = None,
params: t.Dict[str, t.Any] = {},
):
"""
Add a new column to the table.
:param column_class_name:
The column type was traditionally specified as a string, using this
variable. This didn't allow users to define custom column types
though, which is why newer migrations directly reference a
``Column`` subclass using ``column_class``.
:param column_class:
A direct reference to a ``Column`` subclass.
"""
column_class = column_class or getattr(column_types, column_class_name)
if column_class is None:
raise ValueError("Unrecognised column type")
cleaned_params = deserialise_params(params=params)
column = column_class(**cleaned_params)
column._meta.name = column_name
self.add_columns.append(
AddColumnClass(
column=column,
tablename=tablename,
table_class_name=table_class_name,
))
def add_column(
self,
table_class_name: str,
tablename: str,
column_name: str,
column_class_name: str,
params: t.Dict[str, t.Any] = {},
):
column_class = getattr(column_types, column_class_name)
cleaned_params = deserialise_params(params=params)
column = column_class(**cleaned_params)
column._meta.name = column_name
self.add_columns.append(
AddColumnClass(
column=column,
tablename=tablename,
table_class_name=table_class_name,
))
def __sub__(self, value: DiffableTable) -> TableDelta:
if not isinstance(value, DiffableTable):
raise ValueError(
"Can only diff with other DiffableTable instances"
)
if value.class_name != self.class_name:
raise ValueError(
"The two tables don't appear to have the same name."
)
add_columns = [
AddColumn(
table_class_name=self.class_name,
column_name=i._meta.name,
column_class_name=i.__class__.__name__,
params=i._meta.params,
)
for i in (set(self.columns) - set(value.columns))
]
drop_columns = [
DropColumn(
table_class_name=self.class_name,
column_name=i._meta.name,
tablename=value.tablename,
)
for i in (set(value.columns) - set(self.columns))
]
alter_columns: t.List[AlterColumn] = []
for existing_column in value.columns:
column = self.columns_map.get(existing_column._meta.name)
if not column:
# This is a new column - already captured above.
continue
delta = compare_dicts(
serialise_params(column._meta.params).params,
serialise_params(existing_column._meta.params).params,
)
old_params = {
key: existing_column._meta.params.get(key)
for key, _ in delta.items()
}
if delta:
alter_columns.append(
AlterColumn(
table_class_name=self.class_name,
tablename=self.tablename,
column_name=column._meta.name,
params=deserialise_params(delta),
old_params=old_params,
)
)
return TableDelta(
add_columns=add_columns,
drop_columns=drop_columns,
alter_columns=alter_columns,
)
