[jira] Commented: (LUCENE-651) Poor performance race condition in FieldCacheImpl

["Yonik Seeley (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/LUCENE-651?page=comments#action_12449037 ] 
            
Yonik Seeley commented on LUCENE-651:
-------------------------------------

> Wouldn't synchronizing on readerCache be sufficient here?

That would be deadly, esp to something like Solr.  It would kill any ability to warm in the background as *any* index reader filling an entry would block all other readers from using the cache.

> Poor performance race condition in FieldCacheImpl
> -------------------------------------------------
>
>                 Key: LUCENE-651
>                 URL: http://issues.apache.org/jira/browse/LUCENE-651
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>    Affects Versions: 2.0.0
>            Reporter: Oliver Hutchison
>         Assigned To: Otis Gospodnetic
>            Priority: Minor
>         Attachments: LUCENE-651.patch
>
>
> A race condition exists in FieldCacheImpl that causes a significant performance degradation if multiple threads concurrently request a value that is not yet cached. The degradation is particularly noticable in large indexes and when there a many concurent requests for the cached value.
> For the full discussion see the mailing list thread 'Poor performance "race condition" in FieldSortedHitQueue' (http://www.gossamer-threads.com/lists/lucene/java-user/38717).

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