[DERBY-884] allow and use backward scans on indexes.

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 10.1.3.1
• Component/s: SQL, Store
• Labels: derby_triage10_11
• Urgency: Low
• Assignee: Unassigned
• Reporter: Mike Matrigali
• Created: 28/Jan/06 03:12
• Updated: 25/Jun/13 15:03

Description

Improve the access interface to support backward scans, currently only forward scans are supported.

Improve the btree implementation to support backward scans. The structure could support this, the work just has not been done. With
row level locking, concurrent tree splitting, and current assumptions
throughout the access method that scans go top/down, left to right the
work to do a backward scan is harder than doing a forward scan. Also
once the store portion is done, there would be necessary changes to:
optimizer, execution engine, and scan interface to allow the backward
scan. This would be a hard first project.

Improve the optimizer to understand derby indexes now support backward scans.

Improve the execution engine to use the new backward scan interfaces to execute backward scans.

Issue Links

• relates to: DERBY-642 SELECT MAX doesn't use indices optimally