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From Maxim Patramanskij <>
Subject Re[2]: RE : DateFilter.Before/After
Date Thu, 23 Feb 2006 07:42:56 GMT
Hello Erik,

Monday, September 15, 2003, 4:27:27 PM, you wrote:

EH> On Monday, September 15, 2003, at 09:45  AM, Bruce Ritchie wrote:
>> I would suggest *not* using caching inside of filters provided by 
>> lucene but rather provide a wrapper to do the caching. The reason is 
>> that some applications really don't want the libraries they use to be 
>> a source of concern for memory usage. i.e. if I search for a string 
>> using 10,000 different date filters (an extreme example, but possible) 
>> I want the ability to control how those bitsets are going to be > cached.

EH> In the case of QueryFilter, simply construct a new one to avoid caching 
EH> rather than reuse the same instance.  So you have control there as 
EH> well.  The only thing that is cached is a BitSet, so it should be much 
EH> of a memory usage concern.

>> public class CachedFilter extends Filter {
>>     BitSet bits;
>>     Filter filter;
>>     public CachedFilter(Filter filter) {
>>         this.filter = filter;
>>         this.bits = null;
>>     }
>>     public BitSet bits(IndexReader reader) throws IOException {
>>         if (bits != null) {
>>             return bits;
>>         }
>>         bits = filter.bits(reader);
>>         return bits;
>>     }
>> }

EH> You would have problems if you searched a different index or different 
EH> instance of IndexReader even with your caching here.  You should cache 
EH> like QueryFilter does to avoid a potential mismatch with IndexReader 
EH> instances.

EH> But you're implementation is exactly what I was envisioning with the 
EH> added WeakHashMap of QueryFilter.

EH>         Erik

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