jackrabbit-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
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 Mon, 12 Nov 2007 16:21:50 GMT

    [ https://issues.apache.org/jira/browse/JCR-1213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12541821
] 

Ard Schrijvers commented on JCR-1213:
-------------------------------------

"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.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message