Fix service instance relationship ID build bug. (#4075)

* Fix service instance ID build bug.

* Add instance ids into the relation metrics.

oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/source/ServiceInstanceRelation.java

@@ -35,14 +35,14 @@ public class ServiceInstanceRelation extends Source {
     }
 
     @Override public String getEntityId() {
-        return String.valueOf(sourceServiceInstanceId) + Const.ID_SPLIT + String.valueOf(destServiceInstanceId) + Const.ID_SPLIT + String.valueOf(componentId);
+        return String.valueOf(sourceServiceInstanceId) + Const.ID_SPLIT + String.valueOf(destServiceInstanceId);
     }
 
-    @Getter @Setter private int sourceServiceInstanceId;
+    @Getter @Setter @ScopeDefaultColumn.DefinedByField(columnName = "source_service_instance_id") private int sourceServiceInstanceId;
     @Getter @Setter @ScopeDefaultColumn.DefinedByField(columnName = "source_service_id") private int sourceServiceId;
     @Getter @Setter private String sourceServiceName;
     @Getter @Setter private String sourceServiceInstanceName;
-    @Getter @Setter private int destServiceInstanceId;
+    @Getter @Setter @ScopeDefaultColumn.DefinedByField(columnName = "dest_service_instance_id") private int destServiceInstanceId;
     @Getter @Setter @ScopeDefaultColumn.DefinedByField(columnName = "dest_service_id") private int destServiceId;
     @Getter @Setter private String destServiceName;
     @Getter @Setter private String destServiceInstanceName;