ddl's prepare-stage must send the master instance

src/main/java/com/actiontech/dble/backend/mysql/nio/handler/ddl/BaseDDLHandler.java

@@ -101,7 +101,7 @@ public abstract class BaseDDLHandler implements ResponseHandler, ExecutableHandl
                 } else {
                     node.setRunOnSlave(rrs.getRunOnSlave());
                     ShardingNode dn = DbleServer.getInstance().getConfig().getShardingNodes().get(node.getName());
-                    dn.getConnection(dn.getDatabase(), session.getShardingService().isTxStart(), sessionAutocommit, node, this, node);
+                    dn.getConnection(dn.getDatabase(), isMustWrite(), sessionAutocommit, node, this, node);
                 }
             }
         } finally {
@@ -109,6 +109,10 @@ public abstract class BaseDDLHandler implements ResponseHandler, ExecutableHandl
         }
     }
 
+    protected boolean isMustWrite() {
+        return session.getShardingService().isTxStart();
+    }
+
     protected void executeInExistsConnection(BackendConnection conn, RouteResultsetNode node) {
         TraceManager.TraceObject traceObject = TraceManager.serviceTrace(session.getShardingService(), "execute-in-exists-connection");
         try {

src/main/java/com/actiontech/dble/backend/mysql/nio/handler/ddl/MultiNodeDdlPrepareHandler.java

@@ -31,6 +31,11 @@ public class MultiNodeDdlPrepareHandler extends BaseDDLHandler {
         this.traceMessage = "execute-for-ddl-prepare";
     }
 
+    @Override
+    protected boolean isMustWrite() {
+        return true;
+    }
+
     @Override
     protected void innerExecute(BackendConnection conn, RouteResultsetNode node) {
         if (clearIfSessionClosed()) return;