cherry pick pingcap#2691 to release-4.0 (pingcap#2721)

Signed-off-by: sre-bot <sre-bot@pingcap.com>

Co-authored-by: toutdesuite <guizhiluo2014@163.com>

Author: sre-bot

ticdc/ticdc-open-protocol.md

@@ -88,7 +88,7 @@ This section introduces the formats of Row Changed Event, DDL Event, and Resolve
     | :---------- | :----- | :--------------------- |
     | UpdateOrDelete | String |  Identifies whether the row is updated or deleted in the Event. The optional values are `u` or `d`. |
     | Column Name    | String |  The column name.  |
-    | Column Type    | Number |  The column type. See [Column and DDL Type Codes](/ticdc/column-ddl-type-codes.md) for details.  |
+    | Column Type    | Number |  The column type. For details, see [Column Type Code](#column-type-code).  |
     | Where Handle   | Bool   |  Determines whether this column can be the filter condition of the `Where` clause. When this column is unique on the table, `Where Handle` is `true`. |
     | Column Value   | Any    | The Column value.   |
 
@@ -123,7 +123,7 @@ This section introduces the formats of Row Changed Event, DDL Event, and Resolve
     | Parameter       | Type   | Description           |
     | :-------- | :----- | :------------ |
     | DDL Query | String | DDL Query SQL |
-    | DDL Type  | String | The DDL type. See [Column and DDL Type Codes](/ticdc/column-ddl-type-codes.md) for details.    |
+    | DDL Type  | String | The DDL type. For details, see [DDL Type Code](#ddl-type-code).    |
 
 ### Resolved Event
 
@@ -210,3 +210,81 @@ COMMIT;
 13. [partition=0] [key="{\"ts\":415508881038376963,\"t\":3}"] [value=]
 14. [partition=1] [key="{\"ts\":415508881038376963,\"t\":3}"] [value=]
 ```
+
+## Column and DDL type codes
+
+The column and DDL type codes are encodings defined by TiCDC Open Protocol. `Column Type Code` represents the column data type of the Row Changed Event, and `DDL Type Code` represents the DDL statement type of the DDL Event.
+
+### Column Type Code
+
+| Type        | Code | Output Example | Note |
+| :---------- | :--- | :------ | :-- |
+| Decimal     | 0    | {"t":0,"v":"129012.1230000"} | |
+| Tiny/Bool   | 1    | {"t":1,"v":1} | |
+| Short       | 2    | {"t":2,"v":1} | |
+| Long        | 3    | {"t":3,"v":123} | |
+| Float       | 4    | {"t":4,"v":153.123} | |
+| Double      | 5    | {"t":5,"v":153.123} | |
+| Null        | 6    | {"t":6,"v":null} | |
+| Timestamp   | 7    | {"t":7,"v":"1973-12-30 15:30:00"} | |
+| Longlong    | 8    | {"t":8,"v":123} | |
+| Int24       | 9    | {"t":9,"v":123} | |
+| Date        | 10   | {"t":10,"v":"2000-01-01"} | |
+| Duration    | 11   | {"t":11,"v":"23:59:59"} | |
+| Datetime    | 12   | {"t":12,"v":"2015-12-20 23:58:58"} | |
+| Year        | 13   | {"t":13,"v":1970} | |
+| New Date    | 14   | {"t":14,"v":"2000-01-01"} | |
+| Varchar     | 15   | {"t":15,"v":"test"} | The value is encoded in UTF-8. |
+| Bit         | 16   | {"t":16,"v":81} | |
+| JSON        | 245  | {"t":245,"v":"{\\"key1\\": \\"value1\\"}"} | |
+| New Decimal | 246  | {"t":246,"v":"129012.1230000"} | |
+| Enum        | 247  | {"t":247,"v":1} | |
+| Set         | 248  | {"t":248,"v":3} | |
+| Tiny Blob   | 249  | {"t":249,"v":"5rWL6K+VdGV4dA=="} | The value is encoded in Base64. |
+| Medium Blob | 250  | {"t":250,"v":"5rWL6K+VdGV4dA=="} | The value is encoded in Base64. |
+| Long Blob   | 251  | {"t":251,"v":"5rWL6K+VdGV4dA=="} | The value is encoded in Base64. |
+| Blob        | 252  | {"t":252,"v":"5rWL6K+VdGV4dA=="} | The value is encoded in Base64. |
+| Var String  | 253  | {"t":253,"v":"test"} | The value is encoded in UTF-8. |
+| String      | 254  | {"t":254,"v":"test"} | The value is encoded in UTF-8. |
+| Geometry    | 255  |  | Unsupported type. |
+
+### DDL Type Code
+
+| Type                              | Code |
+| :-------------------------------- | :- |
+| Create Schema                     | 1  |
+| Drop Schema                       | 2  |
+| Create Table                      | 3  |
+| Drop Table                        | 4  |
+| Add Column                        | 5  |
+| Drop Column                       | 6  |
+| Add Index                         | 7  |
+| Drop Index                        | 8  |
+| Add Foreign Key                   | 9  |
+| Drop Foreign Key                  | 10 |
+| Truncate Table                    | 11 |
+| Modify Column                     | 12 |
+| Rebase Auto ID                    | 13 |
+| Rename Table                      | 14 |
+| Set Default Value                 | 15 |
+| Shard RowID                       | 16 |
+| Modify Table Comment              | 17 |
+| Rename Index                      | 18 |
+| Add Table Partition               | 19 |
+| Drop Table Partition              | 20 |
+| Create View                       | 21 |
+| Modify Table Charset And Collate  | 22 |
+| Truncate Table Partition          | 23 |
+| Drop View                         | 24 |
+| Recover Table                     | 25 |
+| Modify Schema Charset And Collate | 26 |
+| Lock Table                        | 27 |
+| Unlock Table                      | 28 |
+| Repair Table                      | 29 |
+| Set TiFlash Replica               | 30 |
+| Update TiFlash Replica Status     | 31 |
+| Add Primary Key                   | 32 |
+| Drop Primary Key                  | 33 |
+| Create Sequence                   | 34 |
+| Alter Sequence                    | 35 |
+| Drop Sequence                     | 36 |