[OAK-8002] RDBDocumentStore: add RDB-specific MissingLastRevSeeker

• Type: Technical task
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.12.0, 1.10.3, 1.8.14
• Component/s: rdbmk
• Assignee: Julian Reschke
• Reporter: Julian Reschke
• Created: 24/Jan/19 11:26
• Updated: 16/May/19 11:00
• Resolved: 25/Jan/19 14:12

Description

MissingLastRevSeeker is slow on DB2. This is because the generic MissingLastRevSeeker gets candidates in batches (of 100), but in order to do batching, requires results to be sorted by ID.

For DB2 we by default have indices on both ID and MODIFIED, but contrary to our expection a query that involves both indices does not perform well. Adding a compound index on ID and MODIFIED improves performance, but I'm hesitant to add this just to improve a recovery job.

A more logical approach would be not to require batching/sorting by adopting the approach in MongoMissingLastRevSeeker which doesn't require sorting by ID in the first place.

Issue Links

• is related to: OAK-8311 RDBDocumentStore: allow to turn off RDB-specific MissingLastRevSeeker