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From "Ard Schrijvers (JIRA)" <j...@apache.org>
Subject [jira] Updated: (JCR-1213) UUIDDocId cache does not work properly because of weakReferences in combination with new instance for combined indexreader
Date Fri, 23 Nov 2007 15:38:43 GMT

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

Ard Schrijvers updated JCR-1213:
--------------------------------

    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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