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From: "Uwe Schindler" <uwe@thetaphi.de>
To: <general@lucene.apache.org>
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In-Reply-To: <1291896416219-2057294.post@n3.nabble.com>
Subject: RE: FieldCacheRangeFilter Vs NumericRangeQuery
Date: Thu, 9 Dec 2010 14:20:59 +0100
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> Hi,
>    I run search using FieldChacheFilter and NumericRangeFilter and i am
> getting the similar results. Searchtime is same in both the cases. My
index
> size is 10000000 documents.
> My point is :
> 
> 1. When search is performed using FieldCacheFilter then it caches the
first
> query search result and so next query searches becomes fast. But its not
the
> case with NumericRangeFilter then Why i am getting the same search time in
> both implementations.

It does not cache the filter result unless you use CachingWrapperFilter. It
caches only the actual values for each document in the FieldCache but that
has nothing to do with Filters at all. But it must still review all values
for all documents in the FieldCache to filter the documents. This is faster
for lots of documents matching the query, but for very sparse result sets
this is too expensive. NumericRangeFilter works different, but for it to
work, you have to use a non-infinite precisionStep during indexing with
NumericField, so the index gets bigger. If you only use
FieldCacheRangeFilter, you can index with precisionStep=Integer.MAX_VALUE
(see docs).

I posted you this article, it explains all of this: http://s.apache.org/tk

> 2. I want to know in which case i should use filters. I am performing
searches
> on DateRanges. User just enters a date to search the required document,
will
> it b benificial to use filter in this case.
> As far as i know filters should use when u want to apply some constraints(
eg.
> hide documents which are of "high security") , but in my case too seaching
is
> very fast in case of filter. Should i really use filter?

Since recent versions of Lucene, there is no difference for MultiTermQueries
like NumericRangeQuery, TermRangeQuery,... and replacing them by a filter.
The pro for filters is just for the case where you want to cache them (e.g.
NumericRangeFilter, FieldCacheRangeFilter,...) for later reuse. But for
user-entered arbitrary queries this is not needed and Filters are as fast as
Queries, sometimes the Queries are even faster (this has internal reasons
because of a missing optimization in IndexSearcher).

Uwe