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https://issues.apache.org/jira/browse/LUCENE-2135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12787599#action_12787599
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Christian Kohlschütter commented on LUCENE-2135:
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I haven't followed the aforementioned discussion on the mailing list, but I
think this issue covers a few things that are not mentioned explicitly here.
Maybe it is a good idea to summarize the actual problems/challenges/benefits in
a few sentences?
What I understand is that you plan to add arbitrary (cacheable) attributes to
IndexReader. I suggest to move these features to the IndexCache proposed in
LUCENE-2133. Especially when using decorating IndexReaders (things like
"ReadOnlyIndexReader") you would not want to store attributes separately from
the decorated IndexReader. The same probably applies to SegmentReader with all
its clones.
IndexCache would provide a common base for the extensions you mentioned. (i.e.
you are welcome to apply your patches on top of LUCENE-2133).
> IndexReader.close should forcefully evict entries from FieldCache
> -----------------------------------------------------------------
>
> Key: LUCENE-2135
> URL: https://issues.apache.org/jira/browse/LUCENE-2135
> Project: Lucene - Java
> Issue Type: Bug
> Components: Index
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Fix For: 3.1
>
>
> Spinoff of java-user thread "heap memory issues when sorting by a string
> field".
> We rely on WeakHashMap to hold our FieldCache, keyed by reader. But this
> lacks immediacy on releasing the reference, after a reader is closed.
> WeakHashMap can't free the key until the reader is no longer referenced by
> the app. And, apparently, WeakHashMap has a further impl detail that requires
> invoking one of its methods for it to notice that a key has just become only
> weakly reachable.
> To fix this, I think on IR.close we should evict entries from the FieldCache,
> as long as the sub-readers are truly closed (refCount dropped to 0).
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