[FLINK-35871][doc] Add missed "snapshot" mode to mysql connector star…

…tup options

This closes #3484.

docs/content.zh/docs/connectors/flink-sources/mysql-cdc.md

@@ -261,7 +261,7 @@ Flink SQL> SELECT * FROM orders;
       <td style="word-wrap: break-word;">initial</td>
       <td>String</td>
       <td> MySQL CDC 消费者可选的启动模式，
-         合法的模式为 "initial"，"earliest-offset"，"latest-offset"，"specific-offset" 和 "timestamp"。
+         合法的模式为 "initial"，"earliest-offset"，"latest-offset"，"specific-offset"，"timestamp" 和 "snapshot"。
            请查阅 <a href="#a-name-id-002-a">启动模式</a> 章节了解更多详细信息。</td>
     </tr>
     <tr>
@@ -629,6 +629,7 @@ MySQLSource.builder()
     .startupOptions(StartupOptions.specificOffset("mysql-bin.000003", 4L) // 从指定 binlog 文件名和位置启动
     .startupOptions(StartupOptions.specificOffset("24DA167-0C0C-11E8-8442-00059A3C7B00:1-19")) // 从 GTID 集合启动
     .startupOptions(StartupOptions.timestamp(1667232000000L) // 从时间戳启动
+    .startupOptions(StartupOptions.snapshot()) // 仅读取快照
     ...
     .build()
 ```
@@ -642,6 +643,7 @@ CREATE TABLE mysql_source (...) WITH (
     'scan.startup.mode' = 'latest-offset', -- 从最晚位点启动
     'scan.startup.mode' = 'specific-offset', -- 从特定位点启动
     'scan.startup.mode' = 'timestamp', -- 从特定位点启动
+    'scan.startup.mode' = 'snapshot', -- 仅读取快照
     'scan.startup.specific-offset.file' = 'mysql-bin.000003', -- 在特定位点启动模式下指定 binlog 文件名
     'scan.startup.specific-offset.pos' = '4', -- 在特定位点启动模式下指定 binlog 位置
     'scan.startup.specific-offset.gtid-set' = '24DA167-0C0C-11E8-8442-00059A3C7B00:1-19', -- 在特定位点启动模式下指定 GTID 集合

docs/content.zh/docs/connectors/pipeline-connectors/mysql.md

@@ -172,7 +172,7 @@ pipeline:
       <td style="word-wrap: break-word;">initial</td>
       <td>String</td>
       <td> MySQL CDC 消费者可选的启动模式，
-         合法的模式为 "initial"，"earliest-offset"，"latest-offset"，"specific-offset" 和 "timestamp"。</td>
+         合法的模式为 "initial"，"earliest-offset"，"latest-offset"，"specific-offset"，"timestamp" 和 ""snapshot"。</td>
     </tr>
     <tr>
       <td>scan.startup.specific-offset.file</td>
@@ -280,6 +280,7 @@ pipeline:
 - `latest-offset`：首次启动时，从不对受监视的数据库表执行快照， 连接器仅从 binlog 的结尾处开始读取，这意味着连接器只能读取在连接器启动之后的数据更改。
 - `specific-offset`：跳过快照阶段，从指定的 binlog 位点开始读取。位点可通过 binlog 文件名和位置指定，或者在 GTID 在集群上启用时通过 GTID 集合指定。
 - `timestamp`：跳过快照阶段，从指定的时间戳开始读取 binlog 事件。
+- `snapshot`: 只进行快照阶段，跳过增量阶段，快照阶段读取结束后退出。
 
 例如，可以在 YAML 配置文件中这样指定启动模式：
 
@@ -290,6 +291,7 @@ source:
   scan.startup.mode: latest-offset                      # Start from latest offset
   scan.startup.mode: specific-offset                    # Start from specific offset
   scan.startup.mode: timestamp                          # Start from timestamp
+  scan.startup.mode: snapshot                          # Read snapshot only
   scan.startup.specific-offset.file: 'mysql-bin.000003' # Binlog filename under specific offset startup mode
   scan.startup.specific-offset.pos: 4                   # Binlog position under specific offset mode
   scan.startup.specific-offset.gtid-set: 24DA167-...    # GTID set under specific offset startup mode

docs/content/docs/connectors/flink-sources/mysql-cdc.md

@@ -259,7 +259,7 @@ Connector Options
       <td>optional</td>
       <td style="word-wrap: break-word;">initial</td>
       <td>String</td>
-      <td>Optional startup mode for MySQL CDC consumer, valid enumerations are "initial", "earliest-offset", "latest-offset", "specific-offset" and "timestamp".
+      <td>Optional startup mode for MySQL CDC consumer, valid enumerations are "initial", "earliest-offset", "latest-offset", "specific-offset", "timestamp" and "snapshot".
            Please see <a href="#startup-reading-position">Startup Reading Position</a> section for more detailed information.</td>
     </tr>
     <tr>
@@ -653,6 +653,7 @@ the end of the binlog which means only have the changes since the connector was
 - `specific-offset`: Skip snapshot phase and start reading binlog events from a specific offset. The offset could be
 specified with binlog filename and position, or a GTID set if GTID is enabled on server.
 - `timestamp`: Skip snapshot phase and start reading binlog events from a specific timestamp.
+- `snapshot`: Only the snapshot phase is performed and exits after the snapshot phase reading is completed.
 
 For example in DataStream API:
 ```java
@@ -662,6 +663,7 @@ MySQLSource.builder()
     .startupOptions(StartupOptions.specificOffset("mysql-bin.000003", 4L) // Start from binlog file and offset
     .startupOptions(StartupOptions.specificOffset("24DA167-0C0C-11E8-8442-00059A3C7B00:1-19")) // Start from GTID set
     .startupOptions(StartupOptions.timestamp(1667232000000L) // Start from timestamp
+    .startupOptions(StartupOptions.snapshot()) // Read snapshot only
     ...
     .build()
 ```
@@ -675,6 +677,7 @@ CREATE TABLE mysql_source (...) WITH (
     'scan.startup.mode' = 'latest-offset', -- Start from latest offset
     'scan.startup.mode' = 'specific-offset', -- Start from specific offset
     'scan.startup.mode' = 'timestamp', -- Start from timestamp
+    'scan.startup.mode' = 'snapshot', -- Read snapshot only
     'scan.startup.specific-offset.file' = 'mysql-bin.000003', -- Binlog filename under specific offset startup mode
     'scan.startup.specific-offset.pos' = '4', -- Binlog position under specific offset mode
     'scan.startup.specific-offset.gtid-set' = '24DA167-0C0C-11E8-8442-00059A3C7B00:1-19', -- GTID set under specific offset startup mode

docs/content/docs/connectors/pipeline-connectors/mysql.md

@@ -175,7 +175,7 @@ pipeline:
       <td>optional</td>
       <td style="word-wrap: break-word;">initial</td>
       <td>String</td>
-      <td>Optional startup mode for MySQL CDC consumer, valid enumerations are "initial", "earliest-offset", "latest-offset", "specific-offset" and "timestamp".</td>
+      <td>Optional startup mode for MySQL CDC consumer, valid enumerations are "initial", "earliest-offset", "latest-offset", "specific-offset", "timestamp" and "snapshot".</td>
     </tr>
     <tr>
       <td>scan.startup.specific-offset.file</td>
@@ -290,6 +290,7 @@ The config option `scan.startup.mode` specifies the startup mode for MySQL CDC c
 - `specific-offset`: Skip snapshot phase and start reading binlog events from a specific offset. The offset could be
   specified with binlog filename and position, or a GTID set if GTID is enabled on server.
 - `timestamp`: Skip snapshot phase and start reading binlog events from a specific timestamp.
+- `snapshot`: Only the snapshot phase is performed and exits after the snapshot phase reading is completed.
 
 For example in YAML definition:
 
@@ -300,6 +301,7 @@ source:
   scan.startup.mode: latest-offset                      # Start from latest offset
   scan.startup.mode: specific-offset                    # Start from specific offset
   scan.startup.mode: timestamp                          # Start from timestamp
+  scan.startup.mode: snapshot                          # Read snapshot only
   scan.startup.specific-offset.file: 'mysql-bin.000003' # Binlog filename under specific offset startup mode
   scan.startup.specific-offset.pos: 4                   # Binlog position under specific offset mode
   scan.startup.specific-offset.gtid-set: 24DA167-...    # GTID set under specific offset startup mode