On Oct 5, 2006, at 4:59 AM, Tom Hill wrote:
It's clear that my problem here comes from a lack of understanding
of the semantics of SHOULD, MUST, and MUST_NOT.
I haven't found a clear description of this (except for a brief
comment here http://mail-archives.apache.org/mod_mbox/lucene-java-
dev/200408.mbox/[EMAIL PROTECTED]). Most of the
other descriptions I have found discuss it as if it they were
boolean operators, which they aren't, quite.
Can someone explain to me what the semantics of SHOULD and MUST
are, to the point that I could see from the explanation that
Query: +(name:[A TO C] name:[Q TO Z]) +PHB:NO
would produce the results that I wanted, and
Query: (name:[A TO C] name:[Q TO Z]) +PHB:NO
does not?
With the latter query, since you later said PHB is "NO" for all
documents, you're getting all documents back regardless of the name
field, because you didn't require (MUST) the first clause. The
first query is requiring that PHB:NO __AND__ the name is in those
ranges. The second query is requiring PHB:NO __OR__ the name is in
those ranges.
Or why
Query: (name:[A TO C] name:[Q TO Z]) +PHB:NO
Again, this one selects all documents regardless of the first SHOULD
clause because PHB is "NO" for all documents and the first clause is
a SHOULD, so it does not matter what it matches other than for
ranking purposes.
returns different results than
Query: (name:[A TO C] name:[Q TO Z])
even though PHB is NO for all docs
This is only selecting documents that match either of those ranges.
Thanks for submitting the code example to show exactly what you're
doing.
Obviously, nesting makes it much harder (for me) to understand.
What does it mean to nest a SHOULD nested in a MUST (nested in a ...).
+(name:A OR name:B) +PHB:NO
means that name must be A __OR__ B (has to be one or the other, or
potentially both even), and PHB has to be "NO".
Erik
Thanks again,
Tom
-----------------------------------------------------------Sample
import java.io.IOException;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.*;
import org.apache.lucene.index.*;
import org.apache.lucene.search.*;
import org.apache.lucene.store.*;
public class Should
{
public static final String NAME_FIELD = "name";
public static final String MANAGER_FIELD = "PHB";
public static Document createDoc(String name, String manager)
{
Document d = new Document();
d.add(new Field(NAME_FIELD, name, Field.Store.YES,
Field.Index.UN_TOKENIZED));
d.add(new Field(MANAGER_FIELD, manager,
Field.Store.YES, Field.Index.UN_TOKENIZED));
return d;
}
static BooleanQuery buildQuery(BooleanClause.Occur occur)
{
BooleanQuery bq = new BooleanQuery();
Term lower;
Term upper;
lower = new Term(NAME_FIELD, "A");
upper = new Term(NAME_FIELD, "C");
bq.add(new RangeQuery(lower, upper, true), occur);
lower = new Term(NAME_FIELD, "Q");
upper = new Term(NAME_FIELD, "Z");
bq.add(new RangeQuery(lower, upper, true), occur);
return bq;
}
static BooleanQuery buildQuery2()
{
BooleanQuery mainq = buildQuery
(BooleanClause.Occur.SHOULD);
mainq.add(new TermQuery(new Term(MANAGER_FIELD,
"NO")), BooleanClause.Occur.MUST);
return mainq;
}
static BooleanQuery buildQuery3(BooleanClause.Occur occur)
{
BooleanQuery mainq = new BooleanQuery();
BooleanQuery subq = new BooleanQuery();
Term lower;
Term upper;
lower = new Term(NAME_FIELD, "A");
upper = new Term(NAME_FIELD, "C");
subq.add(new RangeQuery(lower, upper, true),
BooleanClause.Occur.SHOULD);
lower = new Term(NAME_FIELD, "Q");
upper = new Term(NAME_FIELD, "Z");
subq.add(new RangeQuery(lower, upper, true),
BooleanClause.Occur.SHOULD);
mainq.add(subq, occur);
mainq.add(new TermQuery(new Term(MANAGER_FIELD,
"NO")), BooleanClause.Occur.MUST);
return mainq;
}
private static void runQuery(IndexSearcher is, Query q)
throws IOException
{
Hits hits;
System.out.println("Query: " + q);
hits = is.search(q);
System.out.println("Hits: " + hits.length());
for (int docNo = 0; docNo < hits.length(); docNo++)
{
System.out.println("DOC: " + hits.doc(docNo));
}
System.out.println();
}
public static void main(String[] args) throws Exception
{
Directory dir = new RAMDirectory();
Analyzer analyzer = new StandardAnalyzer();
IndexWriter iw = new IndexWriter(dir, analyzer, true);
iw.addDocument(createDoc("Asok", "NO"));
iw.addDocument(createDoc("Dogbert", "NO"));
iw.addDocument(createDoc("Ratbert", "NO"));
iw.close();
IndexSearcher is = new IndexSearcher(dir);
Query q;
q = buildQuery(BooleanClause.Occur.SHOULD);
runQuery(is, q);
q = buildQuery(BooleanClause.Occur.MUST);
runQuery(is, q);
q = buildQuery2();
runQuery(is, q);
q = buildQuery3(BooleanClause.Occur.SHOULD);
runQuery(is, q);
q = buildQuery3(BooleanClause.Occur.MUST);
runQuery(is, q);
is.close();
}
}
----------------Output (I trying to get two results back)
Query: name:[A TO C] name:[Q TO Z]
Hits: 2
DOC: Document<stored/uncompressed,indexed<name:Asok> stored/
uncompressed,indexed<PHB:NO>>
DOC: Document<stored/uncompressed,indexed<name:Ratbert> stored/
uncompressed,indexed<PHB:NO>>
Query: +name:[A TO C] +name:[Q TO Z]
Hits: 0
Query: name:[A TO C] name:[Q TO Z] +PHB:NO
Hits: 3
DOC: Document<stored/uncompressed,indexed<name:Asok> stored/
uncompressed,indexed<PHB:NO>>
DOC: Document<stored/uncompressed,indexed<name:Ratbert> stored/
uncompressed,indexed<PHB:NO>>
DOC: Document<stored/uncompressed,indexed<name:Dogbert> stored/
uncompressed,indexed<PHB:NO>>
Query: (name:[A TO C] name:[Q TO Z]) +PHB:NO
Hits: 3
DOC: Document<stored/uncompressed,indexed<name:Asok> stored/
uncompressed,indexed<PHB:NO>>
DOC: Document<stored/uncompressed,indexed<name:Ratbert> stored/
uncompressed,indexed<PHB:NO>>
DOC: Document<stored/uncompressed,indexed<name:Dogbert> stored/
uncompressed,indexed<PHB:NO>>
Query: +(name:[A TO C] name:[Q TO Z]) +PHB:NO
Hits: 2
DOC: Document<stored/uncompressed,indexed<name:Asok> stored/
uncompressed,indexed<PHB:NO>>
DOC: Document<stored/uncompressed,indexed<name:Ratbert> stored/
uncompressed,indexed<PHB:NO>>
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