mysql: use collation instead of charset (#9156)

- use charset would issue additional 'SET NAMES <VALUE>' queries, set
collation would be better. see: https://github.com/go-sql-driver/mysql#charset

pkg/services/sqlstore/sqlstore.go

@@ -114,7 +114,7 @@ func getEngine() (*xorm.Engine, error) {
 			protocol = "unix"
 		}
 
-		cnnstr = fmt.Sprintf("%s:%s@%s(%s)/%s?charset=utf8mb4&allowNativePasswords=true",
+		cnnstr = fmt.Sprintf("%s:%s@%s(%s)/%s?collation=utf8mb4_unicode_ci&allowNativePasswords=true",
 			DbCfg.User, DbCfg.Pwd, protocol, DbCfg.Host, DbCfg.Name)
 
 		if DbCfg.SslMode == "true" || DbCfg.SslMode == "skip-verify" {

pkg/services/sqlstore/sqlutil/sqlutil.go

@@ -12,7 +12,7 @@ type TestDB struct {
 }
 
 var TestDB_Sqlite3 = TestDB{DriverName: "sqlite3", ConnStr: ":memory:?_loc=Local"}
-var TestDB_Mysql = TestDB{DriverName: "mysql", ConnStr: "grafana:password@tcp(localhost:3306)/grafana_tests?charset=utf8mb4"}
+var TestDB_Mysql = TestDB{DriverName: "mysql", ConnStr: "grafana:password@tcp(localhost:3306)/grafana_tests?collation=utf8mb4_unicode_ci"}
 var TestDB_Postgres = TestDB{DriverName: "postgres", ConnStr: "user=grafanatest password=grafanatest host=localhost port=5432 dbname=grafanatest sslmode=disable"}
 
 func CleanDB(x *xorm.Engine) {

pkg/tsdb/mysql/mysql.go

@@ -66,7 +66,7 @@ func (e *MysqlExecutor) initEngine() error {
 		}
 	}
 
-	cnnstr := fmt.Sprintf("%s:%s@%s(%s)/%s?charset=utf8mb4&parseTime=true&loc=UTC", e.datasource.User, e.datasource.Password, "tcp", e.datasource.Url, e.datasource.Database)
+	cnnstr := fmt.Sprintf("%s:%s@%s(%s)/%s?collation=utf8mb4_unicode_ci&parseTime=true&loc=UTC", e.datasource.User, e.datasource.Password, "tcp", e.datasource.Url, e.datasource.Database)
 	e.log.Debug("getEngine", "connection", cnnstr)
 
 	engine, err := xorm.NewEngine("mysql", cnnstr)