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From Erik Hatcher <>
Subject Re: using the CachingWrapperFilter
Date Thu, 26 May 2005 12:52:24 GMT

On May 26, 2005, at 5:02 AM, M. Mokotov wrote:
> Can someone please explain me how do I use the CachingWrapperFilter?

There is a bit of it demonstrated in Lucene in Action.  Here are some  
snippets that (sort of) describe it:

You can grab the LIA source code from that site also.

> I see that it's built in a decorator way (getting on the  
> constructor another
> filter and decorate it with caching), still I don't see any basic  
> filter to
> be the 'root'.

There are two concrete Filters built in to Lucene - QueryFilter and  
DateFilter.  QueryFilter already has built-in caching, but DateFilter  
does not.  CachingWrapperFilter was created to separate caching from  
the filtering aspects, allowing filters to free themselves from  
having to cache themselves.

> On the tests I saw there is a MockFilter, but I couldn't find it on  
> the
> jars.

We don't package up the test code as a JAR file - but if you check  
out Lucene's code from Subversion you'll find it under src/test

> Do I need to create such a filter myself? Does anyone using the  
> cache needs
> to create his own dummy class?

This all depends on what you're trying to do.  A Filter is used for  
long standing constraints of the document search space.  You would  
not use a "dummy" class, but rather a real filter such as the ones  
just mentioned.  And whether you use the CachingWrapperFilter depends  
on which filter you choose or if you create a custom one.  The Lucene  
in Action source code has an example of a custom Filter.


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