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https://issues.apache.org/jira/browse/SLING-8407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16836946#comment-16836946
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Thomas Mueller commented on SLING-8407:
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[~jebailey] I'm afraid I'm not familiar with the specific requirements of the
job manager. But looking at the code, it seems it makes a lot of sense to run a
query. There are potentially many filter conditions, and running a query allows
to use an index. Assuming the index definition is correct, using an index
reduces the reads from O\(n\) (where n is the number of jobs in the repository)
to roughly O\(1\), assuming the consumer only iterates over a constant number
of entries of the result (which I hope is the case). So in fact you do
sacrifice a lot of speed and efficiency if you traverse and filter yourself.
> which utilizes a tree traversal, which is not the same as an oak traversal
I assume with "oak traversal" you mean "tree traversal within the query
engine", and with "tree traversal" you mean traversing a tree using the JCR API
(getNodes,...). Speed-wise, there is no difference. It's just that running a
query logs a warning in case you traverse a lot, while using the JCR API does
not. (Unfortunately we can't easily implement a warning in this case - the JCR
API is very fine-grained, making this hard.)
> JobManagerImpl.findJobs should prevent traversal
> ------------------------------------------------
>
> Key: SLING-8407
> URL: https://issues.apache.org/jira/browse/SLING-8407
> Project: Sling
> Issue Type: Improvement
> Components: Event
> Reporter: Thomas Mueller
> Priority: Major
>
> The method
> [JobManagerImpl.findJobs|https://github.com/apache/sling-org-apache-sling-event/blob/master/src/main/java/org/apache/sling/event/impl/jobs/JobManagerImpl.java#L373]
> runs a JCR query to find all jobs for a topic.
> It is possible that such a query is running while the repository isn't
> initialized yet, meaning while the index isn't available yet. What is
> happening in this case is that the query is traversing all nodes below that
> path, triggering a warning that the query doesn't use an index. It is
> sometimes happening when a health check is running before the repository is
> initialized (ReplicationQueueHealthCheck and DistributionQueueHealthCheck).
> It doesn't make sense that the query traverses the nodes. It should use an
> index. If the index isn't available yet, it should fail. Therefore, the query
> should use "option(traversal fail)". That would result in an exception that
> can be caught. I will log a related issue to change the health checks to
> process this exception and return HEALTH_CHECK_ERROR for this case.
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