feat: add flow_id and drop_if_exists to DropFlowExpr (#164)

* feat: add `flow_id` and `drop_if_exists` to `DropFlowExpr`

* chore: apply suggestions from CR

* chore: generate code

proto/greptime/v1/ddl.proto

@@ -56,6 +56,8 @@ message CreateFlowExpr {
 message DropFlowExpr {
   string catalog_name = 1;
   string flow_name = 2;
+  FlowId flow_id = 3;
+  bool drop_if_exists = 5;
 }
 
 message CreateTableExpr {
@@ -135,6 +137,8 @@ message DropColumn { string name = 1; }
 
 message TableId { uint32 id = 1; }
 
+message FlowId { uint32 id = 1; }
+
 message ColumnDef {
   string name = 1;
   ColumnDataType data_type = 2;

proto/greptime/v1/flow/server.proto

@@ -59,9 +59,9 @@ message FlowRequest {
 message FlowResponse {
   ResponseHeader header = 1;
   uint64 affected_rows = 2;
-  map<string, bytes> extension = 3;
-  // affected task ids
-  repeated TaskId affected_tasks = 4;
+  // affected flow ids
+  repeated FlowId affected_flows = 3;
+  map<string, bytes> extension = 4;
 }
 
 // Create a flow
@@ -69,7 +69,7 @@ message FlowResponse {
 // Very similar to `ddl.CreateTaskExpr`, 
 // replace `source_table_names` with `source_table_ids`
 message CreateRequest {
-  TaskId flow_id = 1; 
+  FlowId flow_id = 1; 
   repeated TableId source_table_ids = 2;
   TableName sink_table_name = 3;
   bool create_if_not_exists = 4;
@@ -79,6 +79,5 @@ message CreateRequest {
   map<string, string> flow_options = 8;
 }
 
-message DropRequest { TaskId flow_id = 1; }
+message DropRequest { FlowId flow_id = 1; }
 
-message TaskId { uint32 id = 1; }

proto/greptime/v1/meta/common.proto

@@ -52,8 +52,6 @@ message Peer {
   string addr = 2;
 }
 
-message TableId { uint32 id = 1; }
-
 message TimeInterval {
   // The unix timestamp in millis of the start of this period.
   int64 start_timestamp_millis = 1;