feat: support batch ddl (#135)

* feat: support batch create table

* feat: ddl batch

* feat: batch ddl task

* feat: response table ids

proto/greptime/v1/meta/ddl.proto

@@ -39,14 +39,20 @@ message CreateTableTask {
     bytes table_info = 3;
 }
 
+message CreateTableTasks { repeated CreateTableTask tasks = 1; }
+
 message DropTableTask{
     DropTableExpr drop_table = 1;
 }
 
+message DropTableTasks { repeated DropTableTask tasks = 1; }
+
 message AlterTableTask{
     AlterExpr alter_table = 1;
 }
 
+message AlterTableTasks { repeated AlterTableTask tasks = 1; }
+
 message TruncateTableTask {
     TruncateTableExpr truncate_table = 1;
 }
@@ -59,6 +65,9 @@ message SubmitDdlTaskRequest {
         DropTableTask drop_table_task = 3;
         AlterTableTask alter_table_task = 4;
         TruncateTableTask truncate_table_task = 5;
+        CreateTableTasks create_table_tasks = 6;
+        DropTableTasks drop_table_tasks = 7;
+        AlterTableTasks alter_table_tasks = 8;
      }
 }
 
@@ -68,5 +77,8 @@ message SubmitDdlTaskResponse {
     bytes key = 2;
 
     // Returns if table created.
+    // TODO(jeremy): remove it?
     TableId table_id = 4;
+    // Returns if the tables created.
+    repeated TableId table_ids = 5;
 }

proto/greptime/v1/region/server.proto

@@ -47,6 +47,9 @@ message RegionRequest {
     FlushRequest flush = 10;
     CompactRequest compact = 11;
     TruncateRequest truncate = 12;
+    CreateRequests creates = 13;
+    DropRequests drops = 14;
+    AlterRequests alters = 15;
   }
 }
 
@@ -76,6 +79,11 @@ message QueryRequest {
   bytes plan = 3;
 }
 
+// Create a batch of regions at once, usually used to create multiple logical regions
+// at once. Different engines can choose whether to support this request.
+// Metric Engine needs it.
+message CreateRequests { repeated CreateRequest requests = 1; }
+
 message CreateRequest {
   uint64 region_id = 1;
   // Region engine name
@@ -91,6 +99,9 @@ message CreateRequest {
   // TODO: add partition def
 }
 
+// Same as CreateRequests, but for dropping regions.
+message DropRequests { repeated DropRequest requests = 1; }
+
 message DropRequest { uint64 region_id = 1; }
 
 message OpenRequest {
@@ -105,6 +116,8 @@ message OpenRequest {
 
 message CloseRequest { uint64 region_id = 1; }
 
+message AlterRequests { repeated AlterRequest requests = 1; }
+
 message AlterRequest {
   uint64 region_id = 1;
   oneof kind {