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From Doug Cutting <cutt...@lucene.com>
Subject Re: Caching filter wrapper (was Re: RE : DateFilter.Before/After)
Date Mon, 15 Sep 2003 23:25:40 GMT
Bruce Ritchie wrote:
> One thing I saw while tracing back the clone() call is that 
> InputStream.clone() has this remark:
> 
> Expert: Subclasses must ensure that clones may be positioned at
> different points in the input from each other and from the stream they
> were cloned from.
> 
> I'm not actually certain if that's the case for FSInputStream. As I see 
> it I don't think the file variable in the FSInputStream class will be 
> cloned correctly and will cause issues when cloned InputStreams are used.

FSInputStream.file is shared between all clones of an open file.  Access 
to it is synchronized.  This works correctly.  Cloned input streams are 
already used extensively.

> The solution I think is to recreate the FSInputStream.file object 
> whenever a FSInputStream is cloned. I've attached what I think is a fix 
> for the issue below.

This would cause lots more file handles to be opened, and would also 
fail once a file has been deleted.  On UNIX, an open file handle may be 
used after it is deleted, and Lucene leverages this so that updates can 
occur while an index is still being searched.  I don't think there's a 
bug here to be fixed.

Doug


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