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From Erik Hatcher <e...@ehatchersolutions.com>
Subject Re: Keep hits in results
Date Wed, 06 Sep 2006 08:15:18 GMT

On Sep 6, 2006, at 12:56 AM, jacky wrote:

> hi,
>   The following words are quoted from "lucene in action":
>   "There are a couple of implementation approaches:
>  1. Keep the original Hits and IndexSearcher instances available  
> while the
> user is navigating the search results.
>  2. Requery each time the user navigates to a new page.
> It turns out that requerying is most often the best solution.  
> Requerying eliminates
> the need to store per-user state. In a web application, staying  
> stateless (no
> HTTP session) is often desirable. Requerying at first glance seems  
> a waste, but
> Lucene’s blazing speed more than compensates. "
>
>    I am confused about this paragraph. Since Hits is just a simple  
> container of pointers
> to ranked search results, it doesn't load from the index all  
> documents that match a query,
> but only a small portion of them at a time. If we requery, we will  
> get a new hits, why not
> just keeping the orginal Hits which will not waste much memory.

Requerying helps avoid server-side sessions in a web application.   
Hits requires the same IndexSearcher, but in cases where the index is  
changing and a new IndexSearcher is being swapped in, it requires  
more management to keep old IndexSearcher's around until they are no  
longer needed.  I prefer the simplicity of requerying until there is  
actually a performance issue to address.  There is nothing wrong with  
the alternative of keeping Hits around, its just not as simple.

	Erik



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