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https://issues.apache.org/jira/browse/JCR-1213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12543374
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Ard Schrijvers commented on JCR-1213:
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ATM I have been able to change some parts to store in UUIDDocId a reference to
the segmentIndexReader the documentNumber was found in. This means that not
the entire cache is lost when the multi Index changes, but only those parts
that involve a segment change.
Now, I am looking at a clean way to recompute the docNumber, because even if
the segment index reader did not change, the docNumber might (quite likely)
because the multiIndexReader has changed, hence the individual reader offsets
as well.
I'll try to find time next week for it. Perhaps somebody has an idea how to
implement it 'clean', because I do not really like the way I am heading with
changing the SingleTermDocs to store the docNumber with offset, and also store
the docNumber without, to have the doc number available in the segment. This
implies, in DocId I have to cast to SingleTermDocsetc etc which is not
nice.
WDOT? Any ideas? Or should we refactor a few parts, to be able to recompute
the docNumber?
UUIDDocId cache does not work properly because of weakReferences in
combination with new instance for combined indexreader
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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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