Error parsing generated ALTER COLUMN query #122
Description
The generated query when calling alter_column is using the PostGres syntax:
ALTER TABLE table_id ALTER COLUMN column_id DROP NOT NULL
However, the Spanner way of doing this would be:
ALTER TABLE table_id ALTER COLUMN column_id column_type [null_constraint]
e.g. to remove NOT NULL
ALTER TABLE Venue ALTER COLUMN LastUpdateTime TIMESTAMP
e.g. to add NOT NULL
ALTER TABLE Venue ALTER COLUMN LastUpdateTime TIMESTAMP NOT NULL
See #118 (comment) for original example and error.