[cherrypick-2.0] executor: fix drop user bug (#6624) (#7014)

Author: zhexuany

executor/simple.go

@@ -230,18 +230,46 @@ func (e *SimpleExec) executeDropUser(s *ast.DropUserStmt) error {
 			}
 			continue
 		}
+
+		// begin a transaction to delete a user.
+		if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), "begin"); err != nil {
+			return errors.Trace(err)
+		}
 		sql := fmt.Sprintf(`DELETE FROM %s.%s WHERE Host = "%s" and User = "%s";`, mysql.SystemDB, mysql.UserTable, user.Hostname, user.Username)
-		_, _, err = e.ctx.(sqlexec.RestrictedSQLExecutor).ExecRestrictedSQL(e.ctx, sql)
-		if err != nil {
+		if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), sql); err != nil {
+			failedUsers = append(failedUsers, user.String())
+			if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), "rollback"); err != nil {
+				return errors.Trace(err)
+			}
+			continue
+		}
+
+		// delete privileges from mysql.db
+		sql = fmt.Sprintf(`DELETE FROM %s.%s WHERE Host = "%s" and User = "%s";`, mysql.SystemDB, mysql.DBTable, user.Hostname, user.Username)
+		if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), sql); err != nil {
+			failedUsers = append(failedUsers, user.String())
+			if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), "rollback"); err != nil {
+				return errors.Trace(err)
+			}
+			continue
+		}
+
+		// delete privileges from mysql.tables_priv
+		sql = fmt.Sprintf(`DELETE FROM %s.%s WHERE Host = "%s" and User = "%s";`, mysql.SystemDB, mysql.TablePrivTable, user.Hostname, user.Username)
+		if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), sql); err != nil {
+			failedUsers = append(failedUsers, user.String())
+			if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), "rollback"); err != nil {
+				return errors.Trace(err)
+			}
+			continue
+		}
+
+		//TODO: need delete columns_priv once we implement columns_priv functionality.
+		if _, err := e.ctx.(sqlexec.SQLExecutor).Execute(context.Background(), "commit"); err != nil {
 			failedUsers = append(failedUsers, user.String())
 		}
 	}
 	if len(failedUsers) > 0 {
-		// Commit the transaction even if we returns error
-		err := e.ctx.Txn().Commit(sessionctx.SetConnID2Ctx(context.Background(), e.ctx))
-		if err != nil {
-			return errors.Trace(err)
-		}
 		errMsg := "Operation DROP USER failed for " + strings.Join(failedUsers, ",")
 		return terror.ClassExecutor.New(CodeCannotUser, errMsg)
 	}

executor/simple_test.go

@@ -178,6 +178,25 @@ func (s *testSuite) TestUser(c *C) {
 	tk.MustExec(createUserSQL)
 	dropUserSQL = `DROP USER 'test1'@'localhost';`
 	tk.MustExec(dropUserSQL)
+	tk.MustQuery("select * from mysql.db").Check(testkit.Rows(
+		"localhost test testDB Y Y Y Y Y Y Y N Y Y N N N N N N Y N N",
+		"localhost test testDB1 Y Y Y Y Y Y Y N Y Y N N N N N N Y N N] [% dddb_% dduser Y Y Y Y Y Y Y N Y Y N N N N N N Y N N",
+		"% test test Y N N N N N N N N N N N N N N N N N N",
+		"localhost test testDBRevoke N N N N N N N N N N N N N N N N N N N",
+	))
+
+	// Test drop user meet error
+	_, err = tk.Exec(dropUserSQL)
+	c.Assert(terror.ErrorEqual(err, terror.ClassExecutor.New(executor.CodeCannotUser, "")), IsTrue)
+
+	createUserSQL = `CREATE USER 'test1'@'localhost'`
+	tk.MustExec(createUserSQL)
+	createUserSQL = `CREATE USER 'test2'@'localhost'`
+	tk.MustExec(createUserSQL)
+
+	dropUserSQL = `DROP USER 'test1'@'localhost', 'test2'@'localhost', 'test3'@'localhost';`
+	_, err = tk.Exec(dropUserSQL)
+	c.Assert(terror.ErrorEqual(err, terror.ClassExecutor.New(executor.CodeCannotUser, "")), IsTrue)
 }
 
 func (s *testSuite) TestSetPwd(c *C) {