[doc] Add mysql cdc synchronization table comment document. (#5173)

Author: zhuangchong

docs/content/cdc-ingestion/mysql-cdc.md

@@ -265,4 +265,7 @@ to avoid potential name conflict.
 
 1. Chinese characters in records ingested from MySQL are garbled.
 * Try to set `env.java.opts: -Dfile.encoding=UTF-8` in `flink-conf.yaml`(Flink version < 1.19) or `config.yaml`(Flink version >= 1.19)
-(the option is changed to `env.java.opts.all` since Flink-1.17).
+(the option is changed to `env.java.opts.all` since Flink-1.17).
+
+2. Synchronize MySQL Table comment.
+* Synchronize MySQL create table comment to the paimon table, you need to configure `--mysql_conf jdbc.properties.useInformationSchema=true`.

paimon-flink/paimon-flink-cdc/src/test/java/org/apache/paimon/flink/action/cdc/mysql/MySqlSyncTableActionITCase.java

@@ -332,6 +332,7 @@ public void testSchemaEvolutionWithComment() throws Exception {
         mySqlConfig.put("database-name", DATABASE_NAME);
         mySqlConfig.put("table-name", "schema_evolution_comment");
         mySqlConfig.put("debezium.include.schema.comments", "true");
+        mySqlConfig.put("jdbc.properties.useInformationSchema", "true");
 
         MySqlSyncTableAction action =
                 syncTableActionBuilder(mySqlConfig)
@@ -350,6 +351,7 @@ public void testSchemaEvolutionWithComment() throws Exception {
 
     private void testSchemaEvolutionWithCommentImpl(Statement statement) throws Exception {
         FileStoreTable table = getFileStoreTable();
+        assertThat(table.comment()).hasValue("schema_evolution_comment");
         statement.executeUpdate("USE " + DATABASE_NAME);
         statement.executeUpdate("INSERT INTO schema_evolution_comment VALUES (1, 'one')");
 

paimon-flink/paimon-flink-cdc/src/test/resources/mysql/sync_table_setup.sql

@@ -57,7 +57,7 @@ CREATE TABLE schema_evolution_comment (
     _id INT comment 'primary',
     v1 VARCHAR(10) comment 'v1',
     PRIMARY KEY (_id)
-);
+) COMMENT 'schema_evolution_comment';
 
 -- ################################################################################
 --  testAllTypes