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https://issues.apache.org/jira/browse/JCR-1213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12541821
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Ard Schrijvers commented on JCR-1213:
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"return id.getDocumentNumber(this) needs to be replaced by return
id.getDocumentNumber(subReaders[i]); and something similar in
CachingMultiReader."
The above does solve the problem.
In SearchIndex it is more complicated than this. In SearchIndex
public int getParent(int n) throws IOException {
int i = readerIndex(n);
DocId id = subReaders[i].getParentDocId(n - starts[i]);
id = id.applyOffset(starts[i]);
return id.getDocumentNumber(subReaders[i]);
//return id.getDocumentNumber(this);
}
replacing the last line by the subReaders[i] is not enough, because I missed
the part that subReaders[i] returns a CachingMultiReader, keeping the problem
of a cache which will be cleared to often (when a single index changes). This
is also logical, because I did not understand how a parent document number
could be found if the parent would be in a different lucene index.
So, in the id.getDocumentNumber(subReaders[i]) I think I need to check in which
indexReader the parent is found, and use this indexReader instance for the
WeakReference. I'll try to implement this.
> 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
>
>
> 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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