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https://issues.apache.org/jira/browse/OAK-5208?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15712181#comment-15712181
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Stefan Egli commented on OAK-5208:
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Added this to the documentation in
http://svn.apache.org/viewvc?rev=1772220&view=rev
> Improve observation filter switching while events are queued
> ------------------------------------------------------------
>
> Key: OAK-5208
> URL: https://issues.apache.org/jira/browse/OAK-5208
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: jcr
> Affects Versions: 1.5.14
> Reporter: Stefan Egli
>
> OAK-4796 changed the model how commits are filtered for processing by the
> individual observation listeners. Each BackgroundObserver has a queue of
> content changes (ie commits) that are ready for being filtered, converted to
> events and then delivered to listeners.
> Prior to OAK-4796 the filtering of those observation events happened at the
> _head_ of the queue, ie at dequeue time. Thus when switching the filter for
> an observation listener it would be applied to all still queued changes as
> they are being processed.
> With OAK-4796 and its introduction of prefiltering, this filtering now
> happens at the _tail_ of the queue, ie at enqueue time first with the
> _prefilter_, and later on with the _normal_ filter at dequeue time. In
> essense there are now 2 filtering steps. Thus when switching the filter for
> an observation listener and that listener had changes in its queue, the
> effect would be that still enqueued changes would have been gone through the
> prefilter based on the old filter and of the normal filter based on the new
> filter.
> An improvement is to pass the filter applied in the prefilter along in the
> queue and use the same later on for doing the normal filtering. And the
> filter change would then be applied on the prefilter alone.
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