mysqlctl: Move more to use built in MySQL client

executeMysqlScript was still using a `mysql` client binary for
initialization, but there's no reason it needs to do that. We can also
move this to our built in MySQL client to be faster and have less
dependencies here.

Follow up to vitessio#13178 where we already moved things for just the schema
commands.

Signed-off-by: Dirkjan Bussink <d.bussink@gmail.com>

go/vt/mysqlctl/mysqld.go

@@ -651,7 +651,7 @@ func (mysqld *Mysqld) Init(ctx context.Context, cnf *Mycnf, initDBSQLFile string
 		return err
 	}
 	if initDBSQLFile == "" { // default to built-in
-		if err := mysqld.executeMysqlScript(params, strings.NewReader(config.DefaultInitDB)); err != nil {
+		if err := mysqld.executeMysqlScript(ctx, params, config.DefaultInitDB); err != nil {
 			return fmt.Errorf("failed to initialize mysqld: %v", err)
 		}
 		return nil
@@ -663,7 +663,11 @@ func (mysqld *Mysqld) Init(ctx context.Context, cnf *Mycnf, initDBSQLFile string
 		return fmt.Errorf("can't open init_db_sql_file (%v): %v", initDBSQLFile, err)
 	}
 	defer sqlFile.Close()
-	if err := mysqld.executeMysqlScript(params, sqlFile); err != nil {
+	script, err := io.ReadAll(sqlFile)
+	if err != nil {
+		return fmt.Errorf("can't read init_db_sql_file (%v): %v", initDBSQLFile, err)
+	}
+	if err := mysqld.executeMysqlScript(ctx, params, string(script)); err != nil {
 		return fmt.Errorf("can't run init_db_sql_file (%v): %v", initDBSQLFile, err)
 	}
 	return nil
@@ -1006,34 +1010,25 @@ func deleteTopDir(dir string) (removalErr error) {
 	return
 }
 
-// executeMysqlScript executes a .sql script from an io.Reader with the mysql
-// command line tool. It uses the connParams as is, not adding credentials.
-func (mysqld *Mysqld) executeMysqlScript(connParams *mysql.ConnParams, sql io.Reader) error {
-	dir, err := vtenv.VtMysqlRoot()
-	if err != nil {
-		return err
-	}
-	name, err := binaryPath(dir, "mysql")
-	if err != nil {
-		return err
-	}
-	cnf, err := mysqld.defaultsExtraFile(connParams)
+// executeMysqlScript executes the contents of an SQL script as a string.
+// It uses the connParams as is, not adding credentials.
+func (mysqld *Mysqld) executeMysqlScript(ctx context.Context, connParams *mysql.ConnParams, sql string) error {
+	connector := dbconfigs.New(connParams)
+	conn, err := connector.Connect(ctx)
 	if err != nil {
 		return err
 	}
-	defer os.Remove(cnf)
-	args := []string{
-		"--defaults-extra-file=" + cnf,
-		"--batch",
-		"--default-character-set=utf8mb4",
-	}
-	env, err := buildLdPaths()
+	defer conn.Close()
+
+	_, more, err := conn.ExecuteFetchMulti(sql, -1, false)
 	if err != nil {
 		return err
 	}
-	_, _, err = execCmd(name, args, env, dir, sql)
-	if err != nil {
-		return err
+	for more {
+		_, more, _, err = conn.ReadQueryResult(0, false)
+		if err != nil {
+			return err
+		}
 	}
 	return nil
 }

go/vt/mysqlctl/schema.go

@@ -43,22 +43,11 @@ var autoIncr = regexp.MustCompile(` AUTO_INCREMENT=\d+`)
 
 // executeSchemaCommands executes some SQL commands. It uses the dba connection parameters, with credentials.
 func (mysqld *Mysqld) executeSchemaCommands(ctx context.Context, sql string) error {
-	conn, err := getPoolReconnect(ctx, mysqld.dbaPool)
-	if err != nil {
-		return err
-	}
-	defer conn.Recycle()
-	_, more, err := conn.ExecuteFetchMulti(sql, 0, false)
+	params, err := mysqld.dbcfgs.DbaConnector().MysqlParams()
 	if err != nil {
 		return err
 	}
-	for more {
-		_, more, _, err = conn.ReadQueryResult(0, false)
-		if err != nil {
-			return err
-		}
-	}
-	return nil
+	return mysqld.executeMysqlScript(ctx, params, sql)
 }
 
 func encodeEntityName(name string) string {