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List:       lucene-dev
Subject:    Re: svn commit: r164695 - in /lucene/java/trunk: CHANGES.txt src/java/org/apache/lucene/search/Hit.j
From:       Otis Gospodnetic <otis_gospodnetic () yahoo ! com>
Date:       2005-04-27 5:03:49
Message-ID: 20050427050350.83708.qmail () web31105 ! mail ! mud ! yahoo ! com
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Thanks for the Future pointers.  I actually used it, but didn't know it
by name.

Otis

--- Jeremy Rayner <jeremy.rayner@gmail.com> wrote:
> On 4/26/05, Otis Gospodnetic <otis_gospodnetic@yahoo.com> wrote:
> > Also, is "a future for a hit" a typo, or does that actually mean
> > something?  This makes me think of Python's "future", but I'm not
> sure
> > what this means in this context.
> 
> My feeling originally was that as the obtaining of the document 
> was expensive, a Hit should be a bit like the 'Future Value' pattern,
> where a Hit is just a promise to delve into Hits with a certain index
> at some point in the future.
> ( see http://c2.com/cgi/wiki?FutureValue )  
> Which interestingly enough now seems to be implemented in Doug Lea's
> changes for Java 5
> (
>
http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/Future.html
> )
> 
> Although without the asynchronous element, I guess it is just lazy
> initialization.
> 
> An alternative implementation of Hit could be a 'Virtual
> Proxy(GOF:207)' that stores
> a delegate FutureHit or ActualHit, the FutureHit could be the
> starting
> position, but after any call the delegates reference is swapped over
> to ActualHit.  This would eliminate the check of 'resolved' at the
> start
> of each method, and therefore increase perfomance.  However a memory
> overhead would be incurred for the overhead of having three classes
> instead of one.
> So it's a better perfomance vs less memory usage tradeoff.
> 
> Thanks for allowing this change, it has now turned my previous Groovy
> example
> ( http://javanicus.com/blog2/items/178-index.html ) from
> 
> for ( i in 0 ..< hits.length() ) {
>     println(hits.doc(i)["filename"])
> }
> 
> into
> 
> hits.each{
>     println(it.filename)
> }
> 
> which has far less chances for making typos :-)
> 
> jez.
> -- 
> http://javanicus.com/blog2
> 
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