if a table is already using utf8mb4, do not convert it again.

Author: wxiaoguang

docs/content/help/faq.en-us.md

@@ -387,7 +387,7 @@ the `utf8` charset, and connections which use the `utf8` charset will not use th
 
 Please run `gitea doctor convert`, or run `ALTER DATABASE database_name CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;`
 for the database_name and run `ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;`
-for each table in the database.
+for tables which are not using `utf8mb4` in the database.
 
 ## Why are Emoji displaying only as placeholders or in monochrome
 

docs/content/help/faq.zh-cn.md

@@ -390,9 +390,7 @@ SET GLOBAL innodb_large_prefix=1;
 utf8 字符集的表和连接将不会使用它。
 
 请运行 `gitea doctor convert` 或对数据库运行 `ALTER DATABASE database_name CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;`
-并对每个表运行 `ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;`。
-
-您还需要将`app.ini`文件中的数据库字符集设置为`CHARSET=utf8mb4`。
+并对不是 `utf8mb4` 的表运行 `ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;`。
 
 ## 为什么 Emoji 只显示占位符或单色图像
 

models/db/convert.go

@@ -6,6 +6,7 @@ package db
 import (
 	"fmt"
 	"strconv"
+	"strings"
 
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
@@ -34,6 +35,10 @@ func ConvertUtf8ToUtf8mb4() error {
 			return err
 		}
 
+		if strings.HasPrefix(table.Collation, "utf8mb4") {
+			fmt.Printf("skip table %q because it is already using utf8mb4\n", table.Name)
+			continue
+		}
 		if _, err := x.Exec(fmt.Sprintf("ALTER TABLE `%s` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;", table.Name)); err != nil {
 			return err
 		}