fix #2832 Auto-switch search operator to OR when hit count is below threshold

src/main/java/org/codelibs/fess/Constants.java

@@ -250,6 +250,8 @@ public class Constants extends CoreLibConstants {
 
     public static final Pattern LUCENE_RANGE_FIELD_RESERVED_PATTERN = Pattern.compile("([!\\(\\){}\\[\\]\"~\\\\:\\p{Zs}]|(&&)|(\\|\\|))");
 
+    public static final String DEFAULT_QUERY_OPERATOR = "fess.DefaultQueryOperator";
+
     public static final String SEARCH_LOG_ACCESS_TYPE = "searchLogAccessType";
 
     public static final String SEARCH_LOG_ACCESS_TYPE_JSON = "json";

src/main/java/org/codelibs/fess/helper/SearchHelper.java

@@ -45,6 +45,7 @@ import org.codelibs.fess.exception.InvalidQueryException;
 import org.codelibs.fess.mylasta.action.FessUserBean;
 import org.codelibs.fess.mylasta.direction.FessConfig;
 import org.codelibs.fess.query.QueryFieldConfig;
+import org.codelibs.fess.rank.fusion.RankFusionProcessor;
 import org.codelibs.fess.util.BooleanFunction;
 import org.codelibs.fess.util.ComponentUtil;
 import org.codelibs.fess.util.QueryResponseList;
@@ -160,7 +161,22 @@ public class SearchHelper {
 
     protected List<Map<String, Object>> searchInternal(final String query, final SearchRequestParams params,
             final OptionalThing<FessUserBean> userBean) {
-        return ComponentUtil.getRankFusionProcessor().search(query, params, userBean);
+        final RankFusionProcessor rankFusionProcessor = ComponentUtil.getRankFusionProcessor();
+        final List<Map<String, Object>> documentItems = rankFusionProcessor.search(query, params, userBean);
+        if (documentItems instanceof QueryResponseList queryResponseList) {
+            final FessConfig fessConfig = ComponentUtil.getFessConfig();
+            if (queryResponseList.getAllRecordCount() <= fessConfig.getQueryOrsearchMinHitCountAsInteger()) {
+                return LaRequestUtil.getOptionalRequest().map(request -> {
+                    request.setAttribute(Constants.DEFAULT_QUERY_OPERATOR, "OR");
+                    if (logger.isDebugEnabled()) {
+                        logger.debug("The number of hits is {}<={}. Searching again with OR operator.",
+                                queryResponseList.getAllRecordCount(), fessConfig.getQueryOrsearchMinHitCountAsInteger());
+                    }
+                    return rankFusionProcessor.search(query, params, userBean);
+                }).orElse(queryResponseList);
+            }
+        }
+        return documentItems;
     }
 
     public long scrollSearch(final SearchRequestParams params, final BooleanFunction<Map<String, Object>> cursor,

src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java

@@ -856,6 +856,9 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
     /** The key of the configuration. e.g. true */
     String QUERY_REPLACE_TERM_WITH_PREFIX_QUERY = "query.replace.term.with.prefix.query";
 
+    /** The key of the configuration. e.g. 0 */
+    String QUERY_ORSEARCH_MIN_HIT_COUNT = "query.orsearch.min.hit.count";
+
     /** The key of the configuration. e.g. u0021u002Cu002Eu003Fu0589u061Fu06D4u0700u0701u0702u0964u104Au104Bu1362u1367u1368u166Eu1803u1809u203Cu203Du2047u2048u2049u3002uFE52uFE57uFF01uFF0EuFF1FuFF61 */
     String QUERY_HIGHLIGHT_TERMINAL_CHARS = "query.highlight.terminal.chars";
 
@@ -4400,6 +4403,21 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
      */
     boolean isQueryReplaceTermWithPrefixQuery();
 
+    /**
+     * Get the value for the key 'query.orsearch.min.hit.count'. <br>
+     * The value is, e.g. 0 <br>
+     * @return The value of found property. (NotNull: if not found, exception but basically no way)
+     */
+    String getQueryOrsearchMinHitCount();
+
+    /**
+     * Get the value for the key 'query.orsearch.min.hit.count' as {@link Integer}. <br>
+     * The value is, e.g. 0 <br>
+     * @return The value of found property. (NotNull: if not found, exception but basically no way)
+     * @throws NumberFormatException When the property is not integer.
+     */
+    Integer getQueryOrsearchMinHitCountAsInteger();
+
     /**
      * Get the value for the key 'query.highlight.terminal.chars'. <br>
      * The value is, e.g. u0021u002Cu002Eu003Fu0589u061Fu06D4u0700u0701u0702u0964u104Au104Bu1362u1367u1368u166Eu1803u1809u203Cu203Du2047u2048u2049u3002uFE52uFE57uFF01uFF0EuFF1FuFF61 <br>
@@ -9121,6 +9139,14 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
             return is(FessConfig.QUERY_REPLACE_TERM_WITH_PREFIX_QUERY);
         }
 
+        public String getQueryOrsearchMinHitCount() {
+            return get(FessConfig.QUERY_ORSEARCH_MIN_HIT_COUNT);
+        }
+
+        public Integer getQueryOrsearchMinHitCountAsInteger() {
+            return getAsInteger(FessConfig.QUERY_ORSEARCH_MIN_HIT_COUNT);
+        }
+
         public String getQueryHighlightTerminalChars() {
             return get(FessConfig.QUERY_HIGHLIGHT_TERMINAL_CHARS);
         }
@@ -11183,6 +11209,7 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
             defaultMap.put(FessConfig.QUERY_GEO_FIELDS, "location");
             defaultMap.put(FessConfig.QUERY_BROWSER_LANG_PARAMETER_NAME, "browser_lang");
             defaultMap.put(FessConfig.QUERY_REPLACE_TERM_WITH_PREFIX_QUERY, "true");
+            defaultMap.put(FessConfig.QUERY_ORSEARCH_MIN_HIT_COUNT, "0");
             defaultMap.put(FessConfig.QUERY_HIGHLIGHT_TERMINAL_CHARS,
                     "u0021u002Cu002Eu003Fu0589u061Fu06D4u0700u0701u0702u0964u104Au104Bu1362u1367u1368u166Eu1803u1809u203Cu203Du2047u2048u2049u3002uFE52uFE57uFF01uFF0EuFF1FuFF61");
             defaultMap.put(FessConfig.QUERY_HIGHLIGHT_FRAGMENT_SIZE, "60");

src/main/java/org/codelibs/fess/query/parser/QueryParser.java

@@ -31,6 +31,7 @@ import org.apache.lucene.search.Query;
 import org.apache.lucene.search.TermQuery;
 import org.codelibs.fess.Constants;
 import org.codelibs.fess.exception.QueryParseException;
+import org.lastaflute.web.util.LaRequestUtil;
 
 public class QueryParser {
 
@@ -58,7 +59,15 @@ public class QueryParser {
     protected org.apache.lucene.queryparser.classic.QueryParser createQueryParser() {
         final LuceneQueryParser parser = new LuceneQueryParser(defaultField, analyzer);
         parser.setAllowLeadingWildcard(allowLeadingWildcard);
-        parser.setDefaultOperator(defaultOperator);
+        LaRequestUtil.getOptionalRequest().ifPresent(req -> {
+            if (req.getAttribute(Constants.DEFAULT_QUERY_OPERATOR) instanceof String op) {
+                parser.setDefaultOperator(Operator.valueOf(op));
+            } else {
+                parser.setDefaultOperator(defaultOperator);
+            }
+        }).orElse(() -> {
+            parser.setDefaultOperator(defaultOperator);
+        });
         return parser;
     }
 

src/main/resources/fess_config.properties

@@ -443,6 +443,7 @@ query.track.total.hits=10000
 query.geo.fields=location
 query.browser.lang.parameter.name=browser_lang
 query.replace.term.with.prefix.query=true
+query.orsearch.min.hit.count=0
 query.highlight.terminal.chars=u0021u002Cu002Eu003Fu0589u061Fu06D4u0700u0701u0702u0964u104Au104Bu1362u1367u1368u166Eu1803u1809u203Cu203Du2047u2048u2049u3002uFE52uFE57uFF01uFF0EuFF1FuFF61
 query.highlight.fragment.size=60
 query.highlight.number.of.fragments=2