From e736f37bf9be2cdde25c3bd68931e06b81f97a30 Mon Sep 17 00:00:00 2001 From: TomShawn <1135243111@qq.com> Date: Wed, 15 Apr 2020 15:54:26 +0800 Subject: [PATCH 1/4] reference/tools: add ticdc open protocol docs --- TOC.md | 2 + reference/tools/ticdc/column-ddl-type.md | 83 +++++++++ reference/tools/ticdc/open-protocol.md | 211 +++++++++++++++++++++++ reference/tools/ticdc/overview.md | 2 +- 4 files changed, 297 insertions(+), 1 deletion(-) create mode 100644 reference/tools/ticdc/column-ddl-type.md create mode 100644 reference/tools/ticdc/open-protocol.md diff --git a/TOC.md b/TOC.md index 7c5e92ca34de7..074e57dc25535 100644 --- a/TOC.md +++ b/TOC.md @@ -364,6 +364,8 @@ - [Deploy and Use TiCDC](/reference/tools/ticdc/deploy.md) - [Manage TiCDC Cluster and Replication Tasks](/reference/tools/ticdc/manage.md) - [Configure Sink URI](/reference/tools/ticdc/sink.md) + - [TiCDC Open Protocol](/reference/tools/ticdc/open-protocol.md) + - [Column and DDL Type Codes](/reference/tools/ticdc/column-ddl-type.md) + sync-diff-inspector - [Overview](/reference/tools/sync-diff-inspector/overview.md) - [Data Check for Tables with Different Schema or Table Names](/reference/tools/sync-diff-inspector/route-diff.md) diff --git a/reference/tools/ticdc/column-ddl-type.md b/reference/tools/ticdc/column-ddl-type.md new file mode 100644 index 0000000000000..4cfaf5b3c57b1 --- /dev/null +++ b/reference/tools/ticdc/column-ddl-type.md @@ -0,0 +1,83 @@ +--- +title: Column and DDL Type Codes +summary: Learn the column and DDL type codes. +category: reference +--- + +# Column and DDL Type Codes + +The column and DDL type codes are encodings defined by [TiCDC Open Protocol](/reference/tools/ticdc/open-protocol.md). The column type code identifies the column data type in Row Changed Events. The DDL type code identifies the DDL statement type in DDL Events. + +## Column Type Code + +| Type | Code | +| :---------- | :--- | +| Decimal | 0 | +| Tiny | 1 | +| Short | 2 | +| Long | 3 | +| Float | 4 | +| Double | 5 | +| Null | 6 | +| Timestamp | 7 | +| Longlong | 8 | +| Int24 | 9 | +| Date | 10 | +| Duration | 11 | +| Datetime | 12 | +| Year | 13 | +| New Date | 14 | +| Varchar | 15 | +| Bit | 16 | +| JSON | 0xf5 | +| New Decimal | 0xf6 | +| Enum | 0xf7 | +| Set | 0xf8 | +| Tiny Blob | 0xf9 | +| Medium Blob | 0xfa | +| Long Blob | 0xfb | +| Blob | 0xfc | +| Var String | 0xfd | +| String | 0xfe | +| Geometry | 0xff | + +## 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 | diff --git a/reference/tools/ticdc/open-protocol.md b/reference/tools/ticdc/open-protocol.md new file mode 100644 index 0000000000000..859c89302c8a5 --- /dev/null +++ b/reference/tools/ticdc/open-protocol.md @@ -0,0 +1,211 @@ +--- +title: TiCDC Open Protocol +category: reference +--- + +# TiCDC Open Protocol + +TiCDC Open Protocol is a row-level data change notification protocol that provides data sources for monitoring, caching, full-text indexing, analysis engines, and master-slave replication between different databases. TiCDC complies to TiCDC Open Protocol and replicates data changes of TiDB to third-party data media such as MQ (Message Queue). + +TiCDC Open Protocol uses Event as the basic unit to replicate data change events to the downstream. The Event is divided into three categories: + +* Row Changed Event: Represents the data change in a row. When a row is changed, this Event is sent and contains information about the changed row. +* DDL Event: Represents the DDL change. This Event is sent after a DDL statement is successfully executed in the upstream. The DDL Event is broadcasted to every MQ Partition. +* Resolved Event: Represents a special time point before which the Event received is complete. + +## Restrictions + +* In most cases, the Row Changed Event of a version is sent only once, but in special situations such as node failure and network partition, the Row Changed Event of the same version might be sent multiple times. +* Row Changed Events of the same version first sent on the same table are incremented in the order of timestamps (TS) in the Event stream. +* Resolved Events are periodically broadcasted to each MQ Partition. The Resolved Event means that any Event with TS less than Resolved Event TS has been sent to the downstream. +* DDL Events are broadcasted to each MQ Partition. +* Multiple Row Changed Events of a row are sent to the same MQ Partition. + +## Message format + +A Message contains one or more Events, arranged in the following format: + +Key: + +| Offset(Byte) | 0~7 | 8~15 | 16~(15+length1) | ... | ... | +| :----------- | :------ | :--- | :----------- | :--- | :----------- | +| Parameter | Protocol version | Length1 | Event Key1 | LengthN | Event KeyN | + +Value: + +| Offset(Byte) | 0~7 | 8~(7+length1) | ... | ... | +| :----------- | :--- | :-------- | :--- | :------ | +| Parameter | Length1 | Event Value1 | LengthN | Event ValueN | + +* `LengthN` represents the length of the `N`th key/value. +* The length and protocol version are the big-endian `int64` type. +* The version of the current protocol is `1`. + +## Event format + +This section introduces the formats of Row Changed Event, DDL Event, and Resolved Event. + +### Row Changed Event + ++ **Key:** + + ``` + { + "ts":, + "scm":, + "tbl":, + "t":1 + } + ``` + + | Parameter | Type | Description | + | :---------- | :----- | :--------------------- | + | TS | Number | The timestamp of the transaction that causes the row change. | + | Schema Name | String | The name of the schema where the row is in. | + | Table Name | String | The name of the table where the row is in. | + ++ **Value:** + + ``` + { + :{ + :{ + "t":, + "h":, + "v": + }, + :{ + "t":, + "h":, + "v": + } + } + } + ``` + + | Parameter | Type | Description | + | :---------- | :----- | :--------------------- | + | 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](/reference/tools/ticdc/column-ddl-type.md) for details. | + | 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. | + +### DDL Event + ++ **Key:** + + ``` + { + "ts":, + "scm":, + "tbl":
, + "t":2 + } + ``` + + | Parameter | Type | Description | + | :---------- | :----- | :---------------------------------- | + | TS | Number | The timestamp of the transaction that performs the DDL change. | + | Schema Name | String | The schema name of the DDL change, which might be an empty string. | + | Table Name | String | The table name of the DDL change, which might be am empty string. | + ++ **Value:** + + ``` + { + "q":, + "t": + } + ``` + + | Parameter | Type | Description | + | :-------- | :----- | :------------ | + | DDL Query | String | DDL Query SQL | + | DDL Type | String | The DDL type. See [Column and DDL Type Codes](/reference/tools/ticdc/column-ddl-type.md) for details. | + +### Resolved Event + ++ **Key:** + + ``` + { + "ts":, + "t":3 + } + ``` + + | Parameter | Type | Description | + | :---------- | :----- | :------------------------------------------ | + | TS | Number | The Resolved timestamp. Any TS less than this Event has been sent. | + ++ **Value:** None + +## Examples of the Event stream output + +This section shows and displays the output logs of Events. + +Suppose that you execute the following SQL statement in the upstream and the MQ Partition number is 2: + +{{< copyable "sql" >}} + +```sql +CREATE TABLE test.t1(id int primary key, val varchar(16)); +``` + +From the following Log 1 and Log 3, you can see that the DDL Event is broadcasted to all MQ Partitions. + +``` +1. [partition=0] [key="{\"ts\":415508856908021766,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":2}"] [value="{\"q\":\"CREATE TABLE test.t1(id int primary key, val varchar(16))\",\"t\":3}"] +2. [partition=0] [key="{\"ts\":415508856908021766,\"t\":3}"] [value=] +3. [partition=1] [key="{\"ts\":415508856908021766,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":2}"] [value="{\"q\":\"CREATE TABLE test.t1(id int primary key, val varchar(16))\",\"t\":3}"] +4. [partition=1] [key="{\"ts\":415508856908021766,\"t\":3}"] [value=] +``` + +Execute the following SQL statements in the upstream: + +{{< copyable "sql" >}} + +```sql +BEGIN; +INSERT INTO test.t1(id, val) VALUES (1, 'aa'); +INSERT INTO test.t1(id, val) VALUES (2, 'aa'); +UPDATE test.t1 SET val = 'bb' WHERE id = 2; +INSERT INTO test.t1(id, val) VALUES (3, 'cc'); +COMMIT; +``` + ++ From the following Log 5 and Log 6, you can see that Row Changed Events on the same table might be sent to different partitions based on the primary key, but changes to the same row are sent to the same partition so that the downstream can easily process the Event concurrently. ++ From Log 6, multiple changes to the same row in a transaction only send one Row Changed Event. ++ Log 8 is a repeated event of Log 7. Row Changed Event might be repeated, but each version of a first Event is sent orderly. + +``` +5. [partition=0] [key="{\"ts\":415508878783938562,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"u\":{\"id\":{\"t\":3,\"h\":true,\"v\":1},\"val\":{\"t\":15,\"v\":\"YWE=\"}}}"] +6. [partition=1] [key="{\"ts\":415508878783938562,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"u\":{\"id\":{\"t\":3,\"h\":true,\"v\":2},\"val\":{\"t\":15,\"v\":\"YmI=\"}}}"] +7. [partition=0] [key="{\"ts\":415508878783938562,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"u\":{\"id\":{\"t\":3,\"h\":true,\"v\":3},\"val\":{\"t\":15,\"v\":\"Y2M=\"}}}"] +8. [partition=0] [key="{\"ts\":415508878783938562,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"u\":{\"id\":{\"t\":3,\"h\":true,\"v\":3},\"val\":{\"t\":15,\"v\":\"Y2M=\"}}}"] +``` + +Execute the following SQL statements in the upstream: + +{{< copyable "sql" >}} + +```sql +BEGIN; +DELETE FROM test.t1 WHERE id = 1; +UPDATE test.t1 SET val = 'dd' WHERE id = 3; +UPDATE test.t1 SET id = 4, val = 'ee' WHERE id = 2; +COMMIT; +``` + ++ Log 9 is the Row Changed Event of the `Delete` type. This type of Event only contains primary key columns or unique index columns. ++ Log 13 and Log 14 are Resolved Events. The Resolved Event means that in this Partition, any events smaller than the Resolved TS (including Row Changed Event and DDL Event) have been sent. + +``` +9. [partition=0] [key="{\"ts\":415508881418485761,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"d\":{\"id\":{\"t\":3,\"h\":true,\"v\":1}}}"] +10. [partition=1] [key="{\"ts\":415508881418485761,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"d\":{\"id\":{\"t\":3,\"h\":true,\"v\":2}}}"] +11. [partition=0] [key="{\"ts\":415508881418485761,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"u\":{\"id\":{\"t\":3,\"h\":true,\"v\":3},\"val\":{\"t\":15,\"v\":\"ZGQ=\"}}}"] +12. [partition=0] [key="{\"ts\":415508881418485761,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"u\":{\"id\":{\"t\":3,\"h\":true,\"v\":4},\"val\":{\"t\":15,\"v\":\"ZWU=\"}}}"] +13. [partition=0] [key="{\"ts\":415508881038376963,\"t\":3}"] [value=] +14. [partition=1] [key="{\"ts\":415508881038376963,\"t\":3}"] [value=] +``` diff --git a/reference/tools/ticdc/overview.md b/reference/tools/ticdc/overview.md index c159ae3d99f35..219909441a518 100644 --- a/reference/tools/ticdc/overview.md +++ b/reference/tools/ticdc/overview.md @@ -6,7 +6,7 @@ category: reference # TiCDC Overview -[TiCDC](https://github.com/pingcap/ticdc) is a tool for replicating the incremental data of TiDB. This tool is implemented by pulling TiKV change logs. It can restore data to a consistent state with any upstream TSO, and provides "TiCDC Open Protocol" to support other systems to subscribe to data changes. +[TiCDC](https://github.com/pingcap/ticdc) is a tool for replicating the incremental data of TiDB. This tool is implemented by pulling TiKV change logs. It can restore data to a consistent state with any upstream TSO, and provides [TiCDC Open Protocol](/reference/tools/ticdc/open-protocol.md) to support other systems to subscribe to data changes. ## TiCDC Architecture From 720a7dba07a4aa91e3ecbd3d94ad3db96a07bec6 Mon Sep 17 00:00:00 2001 From: TomShawn <1135243111@qq.com> Date: Wed, 15 Apr 2020 17:45:04 +0800 Subject: [PATCH 2/4] align #2763 --- reference/tools/ticdc/column-ddl-type.md | 60 ++++++++++++------------ 1 file changed, 30 insertions(+), 30 deletions(-) diff --git a/reference/tools/ticdc/column-ddl-type.md b/reference/tools/ticdc/column-ddl-type.md index 4cfaf5b3c57b1..b2033cfb9e6d7 100644 --- a/reference/tools/ticdc/column-ddl-type.md +++ b/reference/tools/ticdc/column-ddl-type.md @@ -10,36 +10,36 @@ The column and DDL type codes are encodings defined by [TiCDC Open Protocol](/re ## Column Type Code -| Type | Code | -| :---------- | :--- | -| Decimal | 0 | -| Tiny | 1 | -| Short | 2 | -| Long | 3 | -| Float | 4 | -| Double | 5 | -| Null | 6 | -| Timestamp | 7 | -| Longlong | 8 | -| Int24 | 9 | -| Date | 10 | -| Duration | 11 | -| Datetime | 12 | -| Year | 13 | -| New Date | 14 | -| Varchar | 15 | -| Bit | 16 | -| JSON | 0xf5 | -| New Decimal | 0xf6 | -| Enum | 0xf7 | -| Set | 0xf8 | -| Tiny Blob | 0xf9 | -| Medium Blob | 0xfa | -| Long Blob | 0xfb | -| Blob | 0xfc | -| Var String | 0xfd | -| String | 0xfe | -| Geometry | 0xff | +| 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 Base64. | +| Blob | 252 | {"t":252,"v":"5rWL6K+VdGV4dA=="} | The value is encoded Base64. | +| Var String | 253 | {"t":253,"v":"test"} | The value is encoded UTF-8. | +| String | 254 | {"t":254,"v":"test"} | The value is encoded UTF-8. | +| Geometry | 255 | | Unsupported type | ## DDL Type Code From 130378d32d5c3493b5a3984796bfd844a0180a19 Mon Sep 17 00:00:00 2001 From: TomShawn <1135243111@qq.com> Date: Wed, 15 Apr 2020 18:05:06 +0800 Subject: [PATCH 3/4] fix typos --- reference/tools/ticdc/column-ddl-type.md | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/reference/tools/ticdc/column-ddl-type.md b/reference/tools/ticdc/column-ddl-type.md index b2033cfb9e6d7..4862a351ec150 100644 --- a/reference/tools/ticdc/column-ddl-type.md +++ b/reference/tools/ticdc/column-ddl-type.md @@ -35,10 +35,10 @@ The column and DDL type codes are encodings defined by [TiCDC Open Protocol](/re | 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 Base64. | -| Blob | 252 | {"t":252,"v":"5rWL6K+VdGV4dA=="} | The value is encoded Base64. | -| Var String | 253 | {"t":253,"v":"test"} | The value is encoded UTF-8. | -| String | 254 | {"t":254,"v":"test"} | The value is encoded UTF-8. | +| 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 From 2662f3ec4a1b782f07e1cd2172020628eb8c6aa5 Mon Sep 17 00:00:00 2001 From: TomShawn <1135243111@qq.com> Date: Fri, 24 Apr 2020 19:54:34 +0800 Subject: [PATCH 4/4] address comments --- reference/tools/ticdc/open-protocol.md | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/reference/tools/ticdc/open-protocol.md b/reference/tools/ticdc/open-protocol.md index 859c89302c8a5..d7444a48e61a9 100644 --- a/reference/tools/ticdc/open-protocol.md +++ b/reference/tools/ticdc/open-protocol.md @@ -5,7 +5,7 @@ category: reference # TiCDC Open Protocol -TiCDC Open Protocol is a row-level data change notification protocol that provides data sources for monitoring, caching, full-text indexing, analysis engines, and master-slave replication between different databases. TiCDC complies to TiCDC Open Protocol and replicates data changes of TiDB to third-party data media such as MQ (Message Queue). +TiCDC Open Protocol is a row-level data change notification protocol that provides data sources for monitoring, caching, full-text indexing, analysis engines, and master-slave replication between different databases. TiCDC complies with TiCDC Open Protocol and replicates data changes of TiDB to third-party data medium such as MQ (Message Queue). TiCDC Open Protocol uses Event as the basic unit to replicate data change events to the downstream. The Event is divided into three categories: @@ -16,8 +16,8 @@ TiCDC Open Protocol uses Event as the basic unit to replicate data change events ## Restrictions * In most cases, the Row Changed Event of a version is sent only once, but in special situations such as node failure and network partition, the Row Changed Event of the same version might be sent multiple times. -* Row Changed Events of the same version first sent on the same table are incremented in the order of timestamps (TS) in the Event stream. -* Resolved Events are periodically broadcasted to each MQ Partition. The Resolved Event means that any Event with TS less than Resolved Event TS has been sent to the downstream. +* On the same table, the Row Changed Events of each version which is first sent are incremented in the order of timestamps (TS) in the Event stream. +* Resolved Events are periodically broadcasted to each MQ Partition. The Resolved Event means that any Event with a TS earlier than Resolved Event TS has been sent to the downstream. * DDL Events are broadcasted to each MQ Partition. * Multiple Row Changed Events of a row are sent to the same MQ Partition. @@ -137,13 +137,13 @@ This section introduces the formats of Row Changed Event, DDL Event, and Resolve | Parameter | Type | Description | | :---------- | :----- | :------------------------------------------ | - | TS | Number | The Resolved timestamp. Any TS less than this Event has been sent. | + | TS | Number | The Resolved timestamp. Any TS earlier than this Event has been sent. | + **Value:** None ## Examples of the Event stream output -This section shows and displays the output logs of Events. +This section shows and displays the output logs of the Event stream. Suppose that you execute the following SQL statement in the upstream and the MQ Partition number is 2: @@ -153,7 +153,7 @@ Suppose that you execute the following SQL statement in the upstream and the MQ CREATE TABLE test.t1(id int primary key, val varchar(16)); ``` -From the following Log 1 and Log 3, you can see that the DDL Event is broadcasted to all MQ Partitions. +From the following Log 1 and Log 3, you can see that the DDL Event is broadcasted to all MQ Partitions, and that the Resolved Event is periodically broadcasted to each MQ Partition. ``` 1. [partition=0] [key="{\"ts\":415508856908021766,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":2}"] [value="{\"q\":\"CREATE TABLE test.t1(id int primary key, val varchar(16))\",\"t\":3}"] @@ -176,8 +176,8 @@ COMMIT; ``` + From the following Log 5 and Log 6, you can see that Row Changed Events on the same table might be sent to different partitions based on the primary key, but changes to the same row are sent to the same partition so that the downstream can easily process the Event concurrently. -+ From Log 6, multiple changes to the same row in a transaction only send one Row Changed Event. -+ Log 8 is a repeated event of Log 7. Row Changed Event might be repeated, but each version of a first Event is sent orderly. ++ From Log 6, multiple changes to the same row in a transaction are only sent in one Row Changed Event. ++ Log 8 is a repeated event of Log 7. Row Changed Event might be repeated, but the first Event of each version is sent orderly. ``` 5. [partition=0] [key="{\"ts\":415508878783938562,\"scm\":\"test\",\"tbl\":\"t1\",\"t\":1}"] [value="{\"u\":{\"id\":{\"t\":3,\"h\":true,\"v\":1},\"val\":{\"t\":15,\"v\":\"YWE=\"}}}"]