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https://issues.apache.org/jira/browse/JCR-1213?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ard Schrijvers updated JCR-1213:
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Attachment: JCR-1213.patch
This is a patch solving the WeakReferences and improving the ChildAxisQuery and
DescendantSelfAxisQuery queries speed bu properly caching parent nodex/
hierarchy.
Obviously, I do not really like the dependency in DocId.UUIDDocId on
SingleTermDocs with this patch, and dependency on MultiIndexReader. Perhaps we
can change this later.
For now, perhaps somebody likes to test the patch (specifically on large
repositories with ChildAxisQuery or DescendantSelfAxisQuery ). Test results
for me show an enormous performance gain after the initial queries which are
executed with empty caches.
Hopefully somebody can test it.
> UUIDDocId cache does not work properly because of weakReferences in
> combination with new instance for combined indexreader
> ---------------------------------------------------------------------------------------------------------------------------
>
> Key: JCR-1213
> URL: https://issues.apache.org/jira/browse/JCR-1213
> Project: Jackrabbit
> Issue Type: Improvement
> Components: query
> Affects Versions: 1.3.3
> Reporter: Ard Schrijvers
> Fix For: 1.4
>
> Attachments: JCR-1213.patch
>
>
> Queries that use ChildAxisQuery or DescendantSelfAxisQuery make use of
> getParent() functions to know wether the parents are correct and if the
> result is allowed. The getParent() is called recursively for every hit, and
> can become very expensive. Hence, in DocId.UUIDDocId, the parents are cached.
> Currently, docId.UUIDDocId's are cached by having a WeakRefence to the
> CombinedIndexReader, but, this CombinedIndexReader is recreated all the time,
> implying that a gc() is allowed to remove the 'expensive' cache.
> A much better solution is to not have a weakReference to the
> CombinedIndexReader, but to a reference of each indexreader segment. This
> means, that in getParent(int n) in SearchIndex the return
> return id.getDocumentNumber(this) needs to be replaced by return
> id.getDocumentNumber(subReaders[i]); and something similar in
> CachingMultiReader.
> That is all. Obviously, when a node/property is added/removed/changed, some
> parts of the cached DocId.UUIDDocId will be invalid, but mainly small indexes
> are updated frequently, which obviously are less expensive to recompute.
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