OAK-12051: Use sorting by score as new default.

Author: marvinw

oak-core/src/main/java/org/apache/jackrabbit/oak/Oak.java

@@ -577,11 +577,10 @@ public Oak with(@NotNull Whiteboard whiteboard) {
         }
 
         if (queryEngineSettings != null) {
-            Feature sortUnionQueryByScoreFeature = newFeature(QueryEngineSettings.FT_SORT_UNION_QUERY_BY_SCORE, whiteboard);
-            LOG.info("Registered sort union query by score feature: " + QueryEngineSettings.FT_SORT_UNION_QUERY_BY_SCORE);
-            closer.register(sortUnionQueryByScoreFeature);
-            queryEngineSettings.setSortUnionQueryByScoreFeature(sortUnionQueryByScoreFeature);
-
+            Feature sortUnionQueryLegacyModeFeature = newFeature(QueryEngineSettings.FT_SORT_UNION_QUERY_LEGACY_MODE, whiteboard);
+            LOG.info("Registered sort union query legacy mode feature: " + QueryEngineSettings.FT_SORT_UNION_QUERY_LEGACY_MODE);
+            closer.register(sortUnionQueryLegacyModeFeature);
+            queryEngineSettings.setSortUnionQueryLegacyModeFeature(sortUnionQueryLegacyModeFeature);
             Feature optimizeXPathUnion = newFeature(QueryEngineSettings.FT_OPTIMIZE_XPATH_UNION, whiteboard);
             LOG.info("Registered optimize XPath union feature: " + QueryEngineSettings.FT_OPTIMIZE_XPATH_UNION);
             closer.register(optimizeXPathUnion);
@@ -994,8 +993,8 @@ public void setPrefetchFeature(@Nullable Feature prefetch) {
             settings.setPrefetchFeature(prefetch);
         }
 
-        public void setSortUnionQueryByScoreFeature(@Nullable Feature feature) {
-            settings.setSortUnionQueryByScoreFeature(feature);
+        public void setSortUnionQueryLegacyModeFeature(@Nullable Feature feature) {
+            settings.setSortUnionQueryLegacyModeFeature(feature);
         }
 
         public void setOptimizeXPathUnion(@Nullable Feature feature) {

oak-core/src/main/java/org/apache/jackrabbit/oak/query/QueryEngineSettings.java

@@ -61,7 +61,7 @@ public class QueryEngineSettings implements QueryEngineSettingsMBean, QueryLimit
 
     public static final String OAK_QUERY_PREFETCH_COUNT = "oak.prefetchCount";
 
-    public static final String FT_SORT_UNION_QUERY_BY_SCORE = "FT_OAK-12051";
+    public static final String FT_SORT_UNION_QUERY_LEGACY_MODE = "FT_OAK-12051";
 
     public static final String FT_OPTIMIZE_XPATH_UNION = "FT_OAK-12007";
 
@@ -120,7 +120,7 @@ public class QueryEngineSettings implements QueryEngineSettingsMBean, QueryLimit
     private final long queryLengthErrorLimit = Long.getLong(OAK_QUERY_LENGTH_ERROR_LIMIT, 100 * 1024 * 1024); //100MB
 
     private Feature prefetchFeature;
-    private Feature sortUnionQueryByScoreFeature;
+    private Feature sortUnionQueryLegacyModeFeature;
     private Feature optimizeXPathUnion;
 
     private String autoOptionsMappingJson = "{}";
@@ -226,13 +226,13 @@ public void setFastQuerySize(boolean fastQuerySize) {
         System.setProperty(OAK_FAST_QUERY_SIZE, String.valueOf(fastQuerySize));
     }
 
-    public void setSortUnionQueryByScoreFeature(@Nullable Feature feature) {
-        this.sortUnionQueryByScoreFeature = feature;
+    public void setSortUnionQueryLegacyModeFeature(@Nullable Feature feature) {
+        this.sortUnionQueryLegacyModeFeature = feature;
     }
 
-    public boolean isSortUnionQueryByScoreEnabled() {
-        // disable if the feature toggle is not used
-        return sortUnionQueryByScoreFeature != null && sortUnionQueryByScoreFeature.isEnabled();
+    public boolean isSortUnionQueryLegacyModeEnabled() {
+        // Legacy mode (concatenate) is disabled by default; score-based sorting is the default behavior
+        return sortUnionQueryLegacyModeFeature != null && sortUnionQueryLegacyModeFeature.isEnabled();
     }
 
     public void setOptimizeXPathUnion(@Nullable Feature feature) {

oak-core/src/main/java/org/apache/jackrabbit/oak/query/UnionQueryImpl.java

@@ -324,8 +324,8 @@ public Iterator<ResultRowImpl> getRows() {
             rightIter = ((MeasuringIterator) rightRows).getDelegate();
         }
         if (orderBy == null) {
-            if(!settings.isSortUnionQueryByScoreEnabled()) {
-                // Default old behavior
+            if(settings.isSortUnionQueryLegacyModeEnabled()) {
+                // Legacy mode: concatenate results without score-based merging
                 it = IteratorUtils.chainedIterator(leftIter, rightIter);
             } else {
                 boolean leftHasScore = isScorePresent(left);

oak-core/src/test/java/org/apache/jackrabbit/oak/query/UnionQueryTest.java

@@ -69,8 +69,8 @@ public class UnionQueryTest extends AbstractQueryTest {
     protected ContentRepository createRepository() {
         store = new MemoryNodeStore();
         qeSettings = new QueryEngineSettings();
-        Feature sortFeature = createFeature(true);
-        qeSettings.setSortUnionQueryByScoreFeature(sortFeature);
+        Feature sortFeature = createFeature(false);
+        qeSettings.setSortUnionQueryLegacyModeFeature(sortFeature);
 
         return new Oak(store)
                 .with(new OpenSecurityProvider())
@@ -439,36 +439,37 @@ public void testUnionMergingEmptyIterators() throws Exception {
     }
 
     @Test
-    public void testSortUnionQueryScoreFlagDisabled() throws Exception {
-        QueryEngineSettings disabledSettings = new QueryEngineSettings();
-        Feature sortFeature = createFeature(false);
-        disabledSettings.setSortUnionQueryByScoreFeature(sortFeature);
+    public void testSortUnionQueryLegacyModeEnabled() throws Exception {
+        // When legacy mode is enabled, query results should be concatenated
+        QueryEngineSettings legacySettings = new QueryEngineSettings();
+        Feature legacyModeFeature = createFeature(true);
+        legacySettings.setSortUnionQueryLegacyModeFeature(legacyModeFeature);
         MockQueryBuilder leftQuery = new MockQueryBuilder(true)
                 .addResult("/left/doc1", 0.8)
                 .addResult("/left/doc2", 0.7);
         MockQueryBuilder rightQuery = new MockQueryBuilder(true)
                 .addResult("/right/doc1", 0.9)
                 .addResult("/right/doc2", 0.6);
 
-        UnionQueryImpl unionQuery = new UnionQueryImpl(true, leftQuery.build(), rightQuery.build(), disabledSettings);
+        UnionQueryImpl unionQuery = new UnionQueryImpl(true, leftQuery.build(), rightQuery.build(), legacySettings);
         List<ScoredResult> results = executeUnionAndGetScoredResults(unionQuery);
         assertPathOrder(results, new String[]{"/left/doc1", "/left/doc2", "/right/doc1", "/right/doc2"});
     }
 
     @Test
-    public void testSortUnionQueryScoreFlagIsNull() throws Exception {
-        QueryEngineSettings disabledSettings = new QueryEngineSettings();
-        disabledSettings.setSortUnionQueryByScoreFeature(null);
+    public void testSortUnionQueryLegacyModeNotSet() throws Exception {
+        QueryEngineSettings defaultSettings = new QueryEngineSettings();
+        defaultSettings.setSortUnionQueryLegacyModeFeature(null);
         MockQueryBuilder leftQuery = new MockQueryBuilder(true)
                 .addResult("/left/doc1", 0.8)
                 .addResult("/left/doc2", 0.7);
         MockQueryBuilder rightQuery = new MockQueryBuilder(true)
                 .addResult("/right/doc1", 0.9)
                 .addResult("/right/doc2", 0.6);
 
-        UnionQueryImpl unionQuery = new UnionQueryImpl(true, leftQuery.build(), rightQuery.build(), disabledSettings);
+        UnionQueryImpl unionQuery = new UnionQueryImpl(true, leftQuery.build(), rightQuery.build(), defaultSettings);
         List<ScoredResult> results = executeUnionAndGetScoredResults(unionQuery);
-        assertPathOrder(results, new String[]{"/left/doc1", "/left/doc2", "/right/doc1", "/right/doc2"});
+        assertPathOrder(results, new String[]{"/right/doc1", "/left/doc1", "/left/doc2", "/right/doc2"});
     }
 
     @Test