Alembic Generates Incorrect DDL For ALTER COLUMN... SET DEFAULT ...

[waltaskew]

Alembic generates incorrect DDL for ALTER COLUMN... SET DEFAULT ...
It renders the default values without parentheses, e.g.

ALTER TABLE ... ALTER COLUMN .. SET DEFAULT GENERATE_UUID();
rather than
ALTER TABLE ... ALTER COLUMN .. SET DEFAULT (GENERATE_UUID());

This is because the dialect doesn't implement get_column_default_string and wrap the value in parentheses there as alembic expects.

[olavloite]

Fixed in #733