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From James Dunn <>
Subject Re: Memory usage
Date Wed, 26 May 2004 21:41:40 GMT


I just asked a question regarding how to calculate the
memory requirements for a search.  Does this memory
only get used only during the search operation itself,
or is it referenced by the Hits object or anything
else after the actual search completes?

Thanks again,


--- Doug Cutting <> wrote:
> James Dunn wrote:
> > Also I search across about 50 fields but I don't
> use
> > wildcard or range queries. 
> Lucene uses one byte of RAM per document per
> searched field, to hold the 
> normalization values.  So if you search a 10M
> document collection with 
> 50 fields, then you'll end up using 500MB of RAM.
> If you're using unanalyzed fields, then an easy
> workaround to reduce the 
> number of fields is to combine many in a single
> field.  So, instead of, 
> e.g., using an "f1" field with value "abc", and an
> "f2" field with value 
> "efg", use a single field named "f" with values
> "1_abc" and "2_efg".
> We could optimize this in Lucene.  If no values of
> an indexed field are 
> analyzed, then we could store no norms for the field
> and hence read none 
> into memory.  This wouldn't be too hard to
> implement...
> Doug
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