Hi,
Following up a related post I made on lucene-user yesterday, I've
tracked down what I consider to be a bug in the Query parser relating to
boosting boolean queries.
In short, I think it's reasonable for a user to want to boost all the
terms within a set of parentheses like this:
(fred jim bob)^2.0
However, this fails with the current query parser - the boost factor is
silently ignored.
Please find attached a patch that adds two assertions to the query
parser test, demonstrating the above problem. The patch also includes a
minor change to QueryParser.jj to fix the problem and a tweak to
BooleanQuery.toString() to help test it.
Regards,
--
Lee Mallabone.
Granta Design Ltd.
Index: src/java/org/apache/lucene/queryParser/QueryParser.jj
===================================================================
RCS file: /home/cvspublic/jakarta-lucene/src/java/org/apache/lucene/queryParser/QueryParser.jj,v
retrieving revision 1.21
diff -u -r1.21 QueryParser.jj
--- src/java/org/apache/lucene/queryParser/QueryParser.jj 18 Jul 2002 14:18:42 -0000 1.21
+++ src/java/org/apache/lucene/queryParser/QueryParser.jj 6 Sep 2002 09:40:38 -0000
@@ -424,7 +424,7 @@
Query Clause(String field) : {
Query q;
- Token fieldToken=null;
+ Token fieldToken=null,boost=null;
}
{
[
@@ -434,9 +434,16 @@
(
q=Term(field)
- | <LPAREN> q=Query(field) <RPAREN>
+ | <LPAREN> q=Query(field) <RPAREN> (<CARAT> boost=<NUMBER>)?
)
{
+ if (boost != null) {
+ float f = (float)1.0;
+ try {
+ f = Float.valueOf(boost.image).floatValue();
+ q.setBoost(f);
+ } catch (Exception ignored) { }
+ }
return q;
}
}
Index: src/java/org/apache/lucene/search/BooleanQuery.java
===================================================================
RCS file: /home/cvspublic/jakarta-lucene/src/java/org/apache/lucene/search/BooleanQuery.java,v
retrieving revision 1.4
diff -u -r1.4 BooleanQuery.java
--- src/java/org/apache/lucene/search/BooleanQuery.java 17 Jul 2002 17:38:04 -0000 1.4
+++ src/java/org/apache/lucene/search/BooleanQuery.java 6 Sep 2002 09:40:38 -0000
@@ -142,6 +142,10 @@
/** Prints a user-readable version of this query. */
public String toString(String field) {
StringBuffer buffer = new StringBuffer();
+ if (boost > 1.0) {
+ buffer.append("(");
+ }
+
for (int i = 0 ; i < clauses.size(); i++) {
BooleanClause c = (BooleanClause)clauses.elementAt(i);
if (c.prohibited)
@@ -161,6 +165,12 @@
if (i != clauses.size()-1)
buffer.append(" ");
}
+
+ if (boost > 1.0) {
+ buffer.append(")^");
+ buffer.append(boost);
+ }
+
return buffer.toString();
}
Index: src/test/org/apache/lucene/queryParser/TestQueryParser.java
===================================================================
RCS file: /home/cvspublic/jakarta-lucene/src/test/org/apache/lucene/queryParser/TestQueryParser.java,v
retrieving revision 1.15
diff -u -r1.15 TestQueryParser.java
--- src/test/org/apache/lucene/queryParser/TestQueryParser.java 18 Jul 2002 14:17:41 -0000 1.15
+++ src/test/org/apache/lucene/queryParser/TestQueryParser.java 6 Sep 2002 09:40:39 -0000
@@ -190,6 +190,8 @@
assertTrue(getQuery("\"hello there\"", null) instanceof PhraseQuery);
assertQueryEquals("germ term^2.0", null, "germ term^2.0");
+ assertQueryEquals("(term)^2.0", null, "term^2.0");
+ assertQueryEquals("(germ term)^2.0", null, "(germ term)^2.0");
assertQueryEquals("term^2.0", null, "term^2.0");
assertQueryEquals("term^2", null, "term^2.0");
assertQueryEquals("\"germ term\"^2.0", null, "\"germ term\"^2.0");
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