Changeset 26155 for main/trunk/greenstone2

Timestamp:

2012-09-05T21:06:33+12:00 (12 years ago)

Author:

ak19

Message:

Searching with wildcards on lucene collection now displays term info in search results. But only at section level, not yet at document level. The latter can be accomplished by configuring the multitermquery rewrite method to a setting that could throw an exception if the number of terms exceeds BooleanQuery.MaxClauseCount(). But then searching with wildcards will work like GS2 again (where it works now since GS2's LuceneWrapper uses lucene core library 2.3.2 and GS3's LuceneWrapper3 uses lucene core library 3.3.0.

File:

• main/trunk/greenstone2/common-src/indexers/lucene-gs/src/org/greenstone/LuceneWrapper3/GS2LuceneQuery.java (modified) (2 diffs)

main/trunk/greenstone2/common-src/indexers/lucene-gs/src/org/greenstone/LuceneWrapper3/GS2LuceneQuery.java

@@ -54 +54 @@
 import org.apache.lucene.util.Version;
 
+import org.apache.lucene.search.MultiTermQuery;
+import org.apache.lucene.search.MultiTermQuery.ConstantScoreAutoRewrite;
+
 public class GS2LuceneQuery extends SharedSoleneQuery
 {
@@ -147 +150 @@
 
         Query query = parseQuery(reader, query_parser, query_string, fuzziness);
+
+        // GS2's LuceneWrapper uses lucene-2.3.2. GS3's LuceneWrapper3 works with lucene-3.3.0. 
+        // This change in lucene core library for GS3 had the side-effect that searching on 
+        // "econom*" didn't display what terms it was searching for, whereas it had done so in GS2. 
+
+        // The details of this problem and its current solution are explained in the ticket 
+        // http://trac.greenstone.org/ticket/845
+
+        // We need to change the settings for rewriteMethod in order to get searches on wildcards to 
+        // produce search terms again when the query is rewritten.
+
+        if(query instanceof MultiTermQuery) {
+
+        // default docCountPercent=0.1; default termCountCutoff=350
+
+        // Creating custom cutoff values, taking into account of existing cutoff values
+        MultiTermQuery.ConstantScoreAutoRewrite customRewriteMethod = new MultiTermQuery.ConstantScoreAutoRewrite();
+        customRewriteMethod.setDocCountPercent(100.0);//MultiTermQuery.ConstantScoreAutoRewrite.DEFAULT_DOC_COUNT_PERCENT);
+        customRewriteMethod.setTermCountCutoff(350);
+
+        MultiTermQuery multiTermQuery = (MultiTermQuery)query;
+        multiTermQuery.setRewriteMethod(customRewriteMethod);
+
+        // the above works when searching with wildcards over sections, the following also 
+        // works on book searches, but has been discouraged as it can throw an exception if 
+        // the number of terms exceeds BooleanQuery.getMaxClauseCount().
+        // http://lucene.apache.org/core/3_6_1/api/core/org/apache/lucene/search/MultiTermQuery.html
+
+        //multiTermQuery.setRewriteMethod(MultiTermQuery.CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE);//MultiTermQuery.SCORING_BOOLEAN_QUERY_REWRITE); 
+        }
+
         query = query.rewrite(reader);