Jukka Zitting created OAK-1866:
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Summary: SegmentMK: Inefficient flat node comparisons
Key: OAK-1866
URL: https://issues.apache.org/jira/browse/OAK-1866
Project: Jackrabbit Oak
Issue Type: Bug
Components: core, segmentmk
Affects Versions: 1.0
Reporter: Jukka Zitting
Assignee: Jukka Zitting
Fix For: 1.0.1
The SegmentMK has an optimization for the common case where only a single child
node among many has been updated. For the most part this code works very well,
but there's one code path where this optimization is currently not applied and
as a result a node comparison ends up traversing the full list of child nodes.
The troublesome code path gets triggered when a single child node is updated in
one commit and then another commit does some more complex changes (adds or
removes a node and/or modifies more than a single node).
Usually this isn't too big an issue since traversing even thousands of child
node entries is very fast with the SegmentMK, but things slow down a lot when
there are millions of children. Unfortunately that is exactly what happens with
the UUID index in a large repository with millions of referenceable nodes...
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