Fix empty datasource schema on the Broker when metadata query is disabled

integration-tests/docker/docker-compose.centralized-datasource-schema.yml

@@ -81,7 +81,7 @@ services:
       service: druid-broker
     environment:
       - DRUID_INTEGRATION_TEST_GROUP=${DRUID_INTEGRATION_TEST_GROUP}
-      - druid_sql_planner_metadataRefreshPeriod=PT20S
+      - druid_sql_planner_metadataRefreshPeriod=PT30S
       - druid_sql_planner_disableSegmentMetadataQueries=true
     depends_on:
       - druid-coordinator

integration-tests/src/main/java/org/apache/druid/testing/utils/DataLoaderHelper.java

@@ -23,6 +23,7 @@
 import org.apache.druid.java.util.common.StringUtils;
 import org.apache.druid.java.util.common.logger.Logger;
 import org.apache.druid.testing.clients.CoordinatorResourceTestClient;
+import org.testng.Assert;
 
 public final class DataLoaderHelper
 {
@@ -50,6 +51,9 @@ public void waitUntilDatasourceIsReady(String datasource)
         () -> sqlTestQueryHelper.isDatasourceLoadedInSQL(datasource),
         StringUtils.format("Waiting for [%s] to be ready for SQL queries", datasource)
     );
+
+    Assert.assertTrue(sqlTestQueryHelper.verifyTimeColumnIsPresent(datasource));
+
     LOG.info("Datasource [%s] ready for SQL queries", datasource);
   }
 }

integration-tests/src/main/java/org/apache/druid/testing/utils/SqlTestQueryHelper.java

@@ -69,4 +69,27 @@ public boolean isDatasourceLoadedInSQL(String datasource)
       return false;
     }
   }
+
+  public boolean verifyTimeColumnIsPresent(String datasource)
+  {
+    final SqlQuery query = new SqlQuery(
+        "SELECT __time FROM \"" + datasource + "\" LIMIT 1",
+        null,
+        false,
+        false,
+        false,
+        null,
+        null
+    );
+
+    try {
+      //noinspection unchecked
+      queryClient.query(getQueryURL(broker), query);
+      return true;
+    }
+    catch (Exception e) {
+      LOG.debug(e, "Check query failed");
+      return false;
+    }
+  }
 }

sql/src/main/java/org/apache/druid/sql/calcite/schema/BrokerSegmentMetadataCache.java

@@ -246,6 +246,13 @@ public void refresh(final Set<SegmentId> segmentsToRefresh, final Set<String> da
         continue;
       }
 
+      if (rowSignature.getColumnNames().isEmpty()) {
+        // this case could arise when metadata refresh is disabled on broker
+        // and a new datasource is added
+        log.info("datasource [%s] has empty signature.", dataSource);
+        continue;
+      }
+
       final PhysicalDatasourceMetadata physicalDatasourceMetadata = dataSourceMetadataFactory.build(dataSource, rowSignature);
       updateDSMetadata(dataSource, physicalDatasourceMetadata);
     }

sql/src/test/java/org/apache/druid/sql/calcite/schema/BrokerSegmentMetadataCacheTest.java

@@ -54,6 +54,7 @@
 import org.apache.druid.segment.IndexBuilder;
 import org.apache.druid.segment.QueryableIndex;
 import org.apache.druid.segment.QueryableIndexStorageAdapter;
+import org.apache.druid.segment.Segment;
 import org.apache.druid.segment.TestHelper;
 import org.apache.druid.segment.column.RowSignature;
 import org.apache.druid.segment.incremental.IncrementalIndexSchema;
@@ -86,6 +87,7 @@
 import org.mockito.ArgumentCaptor;
 import org.mockito.Mockito;
 
+import javax.xml.crypto.Data;
 import java.io.File;
 import java.io.IOException;
 import java.util.ArrayList;
@@ -1027,4 +1029,28 @@ public void testInvokeSegmentSchemaAnnounced() throws InterruptedException
     buildSchemaMarkAndTableLatch();
     serverView.invokeSegmentSchemasAnnouncedDummy();
   }
+
+  @Test
+  public void testNoDatasourceSchemaWhenNoSegmentMetadata() throws InterruptedException, IOException
+  {
+    BrokerSegmentMetadataCacheConfig config = new BrokerSegmentMetadataCacheConfig();
+    config.setDisableSegmentMetadataQueries(true);
+
+    BrokerSegmentMetadataCache schema = buildSchemaMarkAndTableLatch(
+        config,
+        new NoopCoordinatorClient()
+    );
+
+    schema.start();
+    schema.awaitInitialization();
+
+    List<DataSegment> segments = schema.getSegmentMetadataSnapshot().values()
+                                .stream()
+                                .map(AvailableSegmentMetadata::getSegment)
+                                .collect(Collectors.toList());
+
+    schema.refresh(segments.stream().map(DataSegment::getId).collect(Collectors.toSet()), Collections.singleton("foo"));
+
+    Assert.assertNull(schema.getDatasource("foo"));
+  }
 }