[DERBY-6882] Add functionality to ALTER TABLE: switch from GENERATED ALWAYS to GENERATED BY DEFAULT

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 10.12.1.1
• Fix Version/s: 10.12.1.2, 10.13.1.0
• Component/s: SQL
• Labels: features
• Assignee: Richard N. Hillegas
• Reporter: Aleksei Kovura
• Created: 31/Mar/16 08:36
• Updated: 24/Apr/16 14:38
• Resolved: 24/Apr/16 14:38

Description

I'm trying to import data from another Derby database with foreignViews tool because system tables got corrupted somehow (see https://issues.apache.org/jira/browse/DERBY-6876). Tables contain generated ID columns (created as "GENERATED ALWAYS"). Importing data and allowing Derby to generate new IDs in generated columns will break relationships between tables (old tables have counter gaps there due to deletes - IDs won't match).
For a clean import without breaking DDL information in DB version control I would like to be able to switch between generated types as follows:

ALTER TABLE table1 ALTER COLUMN col1 SET GENERATED BY DEFAULT [ AS IDENTITY]
ALTER TABLE table1 ALTER COLUMN col1 SET GENERATED ALWAYS [ AS IDENTITY]

Issue Links

• is related to: DERBY-6883 Document the new SET GENERATED clause of ALTER TABLE introduced by DERBY-6882
• relates to: DERBY-6857 Deprecate support for building Derby under JDKs 6 and 7
• relates to: DERBY-6876 Can't create triggers on a table - error 42X94