minor changes

server/src/main/java/org/apache/druid/segment/metadata/AbstractSegmentMetadataCache.java

@@ -271,13 +271,10 @@ protected void cacheExecLoop()
                                                         .plus(config.getMetadataRefreshPeriod())
                                                         .isAfterNow();
 
-              boolean refresh = refreshCondition();
-              boolean shouldRefresh =
-                  isServerViewInitialized &&
+              if (isServerViewInitialized &&
                   !wasRecentFailure &&
                   refreshCondition() &&
-                  (refreshImmediately || nextRefresh < System.currentTimeMillis());
-              if (shouldRefresh) {
+                  (refreshImmediately || nextRefresh < System.currentTimeMillis())) {
                 // We need to do a refresh. Break out of the waiting loop.
                 break;
               }

server/src/main/java/org/apache/druid/segment/metadata/CoordinatorSegmentMetadataCache.java

@@ -99,7 +99,7 @@ public class CoordinatorSegmentMetadataCache extends AbstractSegmentMetadataCach
   private final SqlSegmentsMetadataManager sqlSegmentsMetadataManager;
   private final SegmentReplicationStatusManager segmentReplicationStatusManager;
 
-  // Datasource schema for
+  // Schema for datasources from cold segments
   private final ConcurrentMap<String, DataSourceInformation> coldDatasourceSchema = new ConcurrentHashMap<>();
   private final long coldDatasourceSchemaExecDurationMillis;
   private final ScheduledExecutorService coldDSScehmaExec;
@@ -500,7 +500,6 @@ private Set<SegmentId> filterSegmentWithCachedSchema(Set<SegmentId> segmentIds)
 
   protected void coldDatasourceSchemaExec()
   {
-    log.info("ColdDatasourceSchemaExec");
     Collection<ImmutableDruidDataSource> immutableDataSources =
         sqlSegmentsMetadataManager.getImmutableDataSourcesWithAllUsedSegments();
 
@@ -534,18 +533,29 @@ protected void coldDatasourceSchemaExec()
       final RowSignature.Builder builder = RowSignature.builder();
       columnTypes.forEach(builder::add);
 
-      RowSignature coldDSSignature = builder.build();
-      log.info("Schema for cold ds is %s %s", dataSourceName, coldDSSignature);
-      coldDatasourceSchema.put(dataSourceName, new DataSourceInformation(dataSourceName, coldDSSignature));
+      RowSignature coldSignature = builder.build();
+
+      log.debug("[%s] signature from cold segments is [%s]", dataSourceName, coldSignature);
+
+      coldDatasourceSchema.put(dataSourceName, new DataSourceInformation(dataSourceName, coldSignature));
 
       // update tables map with merged schema
       tables.computeIfPresent(
           dataSourceName,
-          (ds, info) ->
-              new DataSourceInformation(
-                  dataSourceName,
-                  mergeHotAndColdSchema(info.getRowSignature(), coldDSSignature)
-              )
+          (ds, info) -> {
+            RowSignature mergedSignature = mergeHotAndColdSchema(info.getRowSignature(), coldSignature);
+
+            if (!info.getRowSignature().equals(mergedSignature)) {
+              log.info(
+                  "[%s] has new merged signature: %s. hot signature [%s], cold signature [%s].",
+                  ds, mergedSignature, info.getRowSignature(), coldSignature
+              );
+            } else {
+              log.debug("[%s] merged signature is unchanged.", ds);
+            }
+
+            return new DataSourceInformation(ds, mergedSignature);
+          }
       );
     }
 

server/src/test/java/org/apache/druid/segment/metadata/CoordinatorSegmentMetadataCacheTest.java

@@ -1803,8 +1803,7 @@ public void testSameSegmentAddedOnMultipleServer() throws InterruptedException,
     Assert.assertEquals(existingMetadata.getNumReplicas(), currentMetadata.getNumReplicas());
   }
 
-  @Test
-  public void testColdDatasourceSchema() throws IOException
+  private CoordinatorSegmentMetadataCache setupForColdDatasourceSchemaTest()
   {
     DataSegment coldSegment =
         DataSegment.builder()
@@ -1840,7 +1839,7 @@ public void testColdDatasourceSchema() throws IOException
 
     Mockito.when(sqlSegmentsMetadataManager.getImmutableDataSourcesWithAllUsedSegments()).thenReturn(Collections.singletonList(druidDataSource));
 
-    CoordinatorSegmentMetadataCache schema = new CoordinatorSegmentMetadataCache(
+    return new CoordinatorSegmentMetadataCache(
         getQueryLifecycleFactory(walker),
         serverView,
         SEGMENT_CACHE_CONFIG_DEFAULT,
@@ -1853,6 +1852,12 @@ public void testColdDatasourceSchema() throws IOException
         segmentReplicationStatusManager,
         segmentsMetadataManagerConfigSupplier
     );
+  }
+
+  @Test
+  public void testColdDatasourceSchema_mergeSchemaInRefresh() throws IOException
+  {
+    CoordinatorSegmentMetadataCache schema = setupForColdDatasourceSchemaTest();
 
     schema.coldDatasourceSchemaExec();
 
@@ -1873,6 +1878,29 @@ public void testColdDatasourceSchema() throws IOException
     Assert.assertEquals(ColumnType.LONG, rowSignature.getColumnType(columnNames.get(7)).get());
   }
 
+  @Test
+  public void testColdDatasourceSchema_mergeSchemaInColdSchemaExec() throws IOException
+  {
+    CoordinatorSegmentMetadataCache schema = setupForColdDatasourceSchemaTest();
+
+    Set<SegmentId> segmentIds = new HashSet<>();
+    segmentIds.add(segment1.getId());
+    segmentIds.add(segment2.getId());
+
+    schema.refresh(segmentIds, new HashSet<>());
+    schema.coldDatasourceSchemaExec();
+
+    verifyFooDSSchema(schema, 8);
+    RowSignature rowSignature = schema.getDatasource("foo").getRowSignature();
+
+    List<String> columnNames = rowSignature.getColumnNames();
+    Assert.assertEquals("c1", columnNames.get(6));
+    Assert.assertEquals(ColumnType.STRING, rowSignature.getColumnType(columnNames.get(6)).get());
+
+    Assert.assertEquals("c2", columnNames.get(7));
+    Assert.assertEquals(ColumnType.LONG, rowSignature.getColumnType(columnNames.get(7)).get());
+  }
+
   private void verifyFooDSSchema(CoordinatorSegmentMetadataCache schema, int columns)
   {
     final DataSourceInformation fooDs = schema.getDatasource("foo");

server/src/test/java/org/apache/druid/server/http/MetadataResourceTest.java

@@ -39,7 +39,6 @@
 import org.apache.druid.segment.metadata.CoordinatorSegmentMetadataCache;
 import org.apache.druid.segment.metadata.DataSourceInformation;
 import org.apache.druid.server.coordinator.CreateDataSegments;
-import org.apache.druid.server.coordinator.DruidCoordinator;
 import org.apache.druid.server.coordinator.SegmentReplicationStatusManager;
 import org.apache.druid.server.security.AuthConfig;
 import org.apache.druid.server.security.AuthTestUtils;