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From "Ard Schrijvers (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-1213) UUIDDocId cache does not work properly because of weakReferences in combination with new instance for combined indexreader
Date Sun, 18 Nov 2007 13:58:43 GMT

    [ https://issues.apache.org/jira/browse/JCR-1213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12543374

Ard Schrijvers commented on JCR-1213:

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 SingleTermDocs....etc 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 
> ---------------------------------------------------------------------------------------------------------------------------
>                 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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