[DERBY-5151] Don't leak unused identity/sequence values on abnormal exit.

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: SQL
• Labels: derby_triage10_10
• Urgency: Normal
• Assignee: Unassigned
• Reporter: Mark Holster
• Created: 24/Mar/11 21:20
• Updated: 28/Sep/12 04:45

Description

Currently, a sequence in Derby always uses a pre allocating cache. I'm working on an usecase which requires a number to increase with a fixed value. The usecase fails after a restart because of the pre allocating cache.

I've created a patch that adds the options CACHE | NO CACHE to the create sequence statement. When no cache is provided, the pre allocating cache size will be set to 1, which results in a "no cache sequence".
I've followed the CYCLE | NO CYCLE code as much as possible. Tested it in my own app and it seems to work fine.

RH: Note that part of this issue has been addressed by the work on DERBY-4437. Sequence values will NOT leak now if you perform an orderly shutdown of your database. However, values still leak if the VM exits before the database has been shutdown. I have changed this issue's title to indicate that the remaining work applies to both sequences and identity columns.

Issue Links

• blocks: DERBY-712 Support for sequences
• relates to: DERBY-4437 Concurrent inserts into table with identity column perform poorly