[OAK-6867] Enable index hints on UUID lookup query

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.7.14, 1.8.0
• Component/s: query
• Epic Link: indexer resilience
• Sprint: L16
• Assignee: Thomas Mueller
• Reporter: Alex Deparvu
• Created: 25/Oct/17 10:06
• Updated: 08/Oct/19 15:22
• Resolved: 07/Dec/17 10:11

Description

For the UUID lookup query I enabled the (recently added) query hints support where you can specify the index you want to be used and I got an interesting speedup in the benchmarks:

Hint disabled, lookup by query
# UUIDLookupTest                   C     min     10%     50%     90%     max       N 
No of indexes (60) 60, Lookup by (lookupByQuery)[query] 
Oak-Segment-Tar                    1       5       5       6       7      27    9837

Hint enabled, lookup by query
# UUIDLookupTest                   C     min     10%     50%     90%     max       N 
No of indexes (60) 60, Lookup by (lookupByQuery)[query] 
Oak-Segment-Tar                    1       5       5       6       7      13   10128

Hint enabled, lookup by getNode
# UUIDLookupTest                   C     min     10%     50%     90%     max       N 
No of indexes (60) 60, Lookup by (lookupByQuery)[Session#getNodeByIdentifier] 
Oak-Segment-Tar                    1       5       6       6       7      13    9447


Hint disabled, lookup by getNode
# UUIDLookupTest                   C     min     10%     50%     90%     max       N 
No of indexes (60) 60, Lookup by (lookupByQuery)[Session#getNodeByIdentifier] 
Oak-Segment-Tar                    1       3       3       3       4       8   17504

It seems the cost shortcut is reducing the overall time, but cannot say for sure where this change comes from.
The only change I did was to add option(index name uuid) to this query [0]

tmueller, chetanm what do you think?

[0] https://github.com/apache/jackrabbit-oak/blob/trunk/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/identifier/IdentifierManager.java#L356