[
https://issues.apache.org/jira/browse/OAK-6867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16281519#comment-16281519
]
Thomas Mueller commented on OAK-6867:
-------------------------------------
Two options that won't work (in my view):
* If we use "option(index name uuid)", then we can't slowly switch the uuid
index to another index type (eg. Lucene) any longer. Slowly switching means
first create a second index "uuidLucene", then once it's ready set "disabled"
to true in the uuid index. So, hardcoding index names isn't a good idea.
* If we use "option(index tag uuid)", then we require that all uuid indexes
(/oak:index/uuid, /oak:index/uuidLucene once we have that) have the property
"tags" set to ["uuid"]. We could add that flag at repository startup to the
uuid index. However, if this doesn't work for some reason (eg. the repository
is read-only), or happens slightly too late (possibly a race condition), then
the query would fail. So I consider this risky that late in the release cycle.
> Enable index hints on UUID lookup query
> ---------------------------------------
>
> Key: OAK-6867
> URL: https://issues.apache.org/jira/browse/OAK-6867
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: query
> Reporter: Alex Deparvu
> Assignee: Thomas Mueller
> Fix For: 1.8
>
>
> 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:
> {noformat}
> 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
> {noformat}
> 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
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
