Chetan Mehrotra created OAK-4404:
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Summary: DocumentNodeState.childNodeEntries perform more fetches
than required
Key: OAK-4404
URL: https://issues.apache.org/jira/browse/OAK-4404
Project: Jackrabbit Oak
Issue Type: Improvement
Components: documentmk
Reporter: Chetan Mehrotra
Assignee: Chetan Mehrotra
Priority: Minor
{{DocumentNodeState}} lazily fetches the child node entries in batches of
increasing fetchSize starting at 100. Now we have a commit where we add 200
child nodes under /a. This list of child node entries would be cached (all 200
entries).
Now if the code later tries to read all these recently added child nodes then
DocumentNodeState would perform a fetch for initial 100. The iterator that is
returned though is not limited to 100 and returns all 200 entries. As the
iterator proceeds {{currentRemaining}} moves to -100 (it starts at 100 the
expected fetchSize).
This causes hasMore to perform one more fetch which then results in a remote
call as its a cache miss (cache key inlcudes the base name from where the list
should start).
This extra call can be avoided if the {{DocumentNodeStore}} can convey the
information that the returned iterator is complete and in such a case
DocumentNodeState does not have to rely on its internal bookkeeping.
This change would also be required for secondary node store based persistent
cache to work. In those case the cache would be able to provide complete
iterator but DocumentNodeState would not be able to make best use of this if it
sticks to the fetch based approach
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