FAQ
if you have many terms across the fields, you might want to invoke
IndexReader's setTermInfosIndexDivisor() method, which would
reduce the in memory term infos used to lookup idf, but a (slightly)
slower search.



From: gsingers@apache.org
To: java-user@lucene.apache.org
Subject: Re: Is it possible to get only one Field from a Document?
Date: Wed, 11 Jun 2008 08:22:22 -0400

For the record, Hits.id(int i) returns the document number. Note,
though, that Hits is now deprecated, as pointed out by the link to
1290, so going the TopDocs route is probably better anyway.

-Grant
On Jun 11, 2008, at 7:43 AM, Daan de Wit wrote:

This is possible, you need to provider a FieldSelector to
IndexReader#document(docId, selector). This won't work with Hits
though, because Hits does not expose the document number, so you
need to roll your own solution using TopDocs or HitCollector, for
information see the discussion in this issue: https://issues.apache.org/jira/browse/LUCENE-1290

Kind regards,
Daan de Wit

-----Original Message-----
From: Marcelo Schneider
Sent: Wednesday, June 11, 2008 13:29
To: java-user@lucene.apache.org
Subject: Is it possible to get only one Field from a Document?

I have a environment where we have indexed a DB with about 6mil
entries
with Lucene, and each row has 25 columns. 20 cols have integer codes
used as filters (indexed/unstored), and the other 5 have (very) large
texts (also indexed/unstored). Currently the search I'm doing is
like this:

Hits hits = searcher.search(query);
for (int i = 0; i < this.hits.length(); i++) {
Document doc = this.hits.doc(i);
String s = doc.get("fieldWanted");
// does everything with the result, etc
}

We are trying to reduce memory usage, however. Is it possible to
return
a Document object with just the Fields I really need? In the example,
each Document have 25 fields, and I just need one... would this
theoretically make any difference?




--

Marcelo Frantz Schneider
SIC - TCO - Tecnologia em Engenharia do Conhecimento
DÍGITRO TECNOLOGIA
E-mail: marcelo.schneider@digitro.com.br
Site: www.digitro.com


--
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Grant Ingersoll
http://www.lucidimagination.com

Lucene Helpful Hints:
http://wiki.apache.org/lucene-java/BasicsOfPerformance
http://wiki.apache.org/lucene-java/LuceneFAQ








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