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-# DataNode DDL Flush Design
-
-update: 5.19.2021, by [Goose](https://github.com/XuanYang-cn)
-update: 5.21.2021, by [Goose](https://github.com/XuanYang-cn)
-update: 6.04.2021, by [Goose](https://github.com/XuanYang-cn)
-
-**THIS IS OUTDATE**
-
-## Background
-
-Data Definition Language (DDL) is a language used to define data structures and modify data<sup>[1](#techterms1)</sup>.
-In Milvus terminology, for instance, `CreateCollection` and `DropPartition` etc. are DDL. In order to recover
-or redo DD operations, DataNode flushes DDLs into persistent storages.
-
-Before this design, DataNode buffers DDL chunks by collection, flushes all buffered data in manul/auto flush.
-
-Now in [DataNode Recovery Design](datanode_recover_design_0513_2021.md), flowgraph : vchannel = 1 : 1, and insert
-data of one segment is always in one vchannel. So each flowgraph concerns only about ONE specific collection. For
-DDL channels, one flowgraph only cares about DDL operations of one collection. In this case,
-I don't think it's necessary to auto-flush ddl anymore.
-
-## Goals
-
--  Flowgraph knows about which segment/collection to concern.
--  DDNode update masPositions once it buffers ddl about the collection.
--  DDNode won't auto flush.
--  In manul-flush, a background flush-complete goroutinue waits for DDNode and InsertBufferNode both done
-flushing, waiting for both binlog paths.
-
-## Detailed design
-
-1. Redesign of DDL binlog paths and etcd paths for these binlog paths
-
-
-DDL flushes based on a manul flush of a segment.
-
-**Former design**
-```
-# minIO/S3 ddl binlog paths
-${tenant}/data_definition_log/${collection_id}/ts/${log_idx}
-${tenant}/data_definition_log/${collection_id}/ddl/${log_idx}
-
-# etcd paths for ddl binlog paths
-${prefix}/${collectionID}/${idx}
-```
-
-The minIO/S3 ddl binlog paths seems ok, but etcd paths aren't clear, especially when we want to relate a ddl flush
-to a certain segment flush.
-
-**Redesign**
-```
-# etcd paths for ddl binlog paths
-${prefix}/${collectionID}/${segmentID}/${idx}
-```
-
-```
-message PositionPair {
-  internal.MsgPosition start_position = 1;
-  internal.MsgPosition end_position = 2;
-}
-
-message SaveBinlogPathsRequest {
-    common.MsgBase base = 1;
-    int64 segmentID = 2;
-    int64 collectionID = 3;
-    ID2PathList field2BinlogPaths = 4;
-    repeated DDLBinlogMeta = 5;
-    PositionPair dml_position = 6;
-    PositionPair ddl_position =7;
- }
-```
-
-## TODOs
-
-1. Refactor auto-flush of ddNode
-3. Refactor etcd paths
-
-<a name="techterms1">[1]</a>: *[techterms.com](https://techterms.com/definition/ddl#:~:text=Stands%20for%20%22Data%20Definition%20Language,SQL%2C%20the%20Structured%20Query%20Language)*