[DERBY-4800] Allow bulk scan of LOB tables with holdable cursors

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 10.7.1.1
• Component/s: SQL
• Labels: derby_triage10_10
• Urgency: Normal
• Bug behavior facts: Performance
• Assignee: Unassigned
• Reporter: Knut Anders Hatlen
• Created: 16/Sep/10 12:55
• Updated: 28/Sep/12 18:28

Description

DERBY-1511 disabled bulk scans for tables with LOBs if the cursor was holdable. This was done to work around a bug, but it had a very negative impact on queries that scanned tables that contained relatively small LOBs. It would be good if we could find a safe way to re-enable bulk scans for these queries.

The problem now is that the lob containers are closed on the transaction boundaries, so the buffered values will be dead on arrival when we call next() after a commit(). If we could find a way to make the containers survive across the transaction boundary, or make it possible to reopen the container, it should be safe to re-enable the bulk scans.

Issue Links

• relates to: DERBY-1511 SELECT clause without a WHERE, causes an Exception when extracting a Blob from a database