Source code for squabble.rules.disallow_change_column_type

from pglast.enums import AlterTableType

from squabble.message import Message
from squabble.rules import BaseRule

[docs]class DisallowChangeColumnType(BaseRule): """ Prevent changing the type of an existing column. Configuration: :: { "DisallowChangeColumnType": {} } """
[docs] class ChangeTypeNotAllowed(Message): """ Trying to change the type of an existing column may hold a full table lock while all of the rows are modified. Additionally, changing the type of a column may not be backwards compatible with code that has already been deployed. Instead, try adding a new column with the updated type, and then migrate over. For example, to migrate a column from ``type_a`` to ``type_b``. .. code-block:: sql ALTER TABLE foo ADD COLUMN bar_new type_b; UPDATE foo SET bar_new = cast(bar_old, type_b); -- Deploy server code to point to new column ALTER TABLE foo DROP COLUMN bar_old; """ CODE = 1003 TEMPLATE = 'cannot change type of existing column "{col}"'
def enable(self, ctx, _config): ctx.register('AlterTableCmd', lambda c, n: self._check(c, n)) def _check(self, ctx, node): """ Node is an `AlterTableCmd`: { 'AlterTableCmd': { 'def': { 'ColumnDef': { 'colname': 'bar', 'constraints': [{'Constraint': {'contype': 2, 'location': 35}}] } } } } """ # We only care about changing the type of a column if node.subtype != AlterTableType.AT_AlterColumnType: return ty = node['def'].typeName issue = self.ChangeTypeNotAllowed(, node=ty)