br: skip template system table __TiDB_BR_Temporary_mysql when backup

br/pkg/backup/client.go

@@ -528,7 +528,7 @@ func BuildBackupRangeAndSchema(
 
 	for _, dbInfo := range dbs {
 		// skip system databases
-		if !tableFilter.MatchSchema(dbInfo.Name.O) || util.IsMemDB(dbInfo.Name.L) {
+		if !tableFilter.MatchSchema(dbInfo.Name.O) || util.IsMemDB(dbInfo.Name.L) || utils.IsTemplateSysDB(dbInfo.Name) {
 			continue
 		}
 

br/pkg/utils/schema.go

@@ -16,6 +16,7 @@ import (
 
 // temporaryDBNamePrefix is the prefix name of system db, e.g. mysql system db will be rename to __TiDB_BR_Temporary_mysql
 const temporaryDBNamePrefix = "__TiDB_BR_Temporary_"
+const temporarySysDB = temporaryDBNamePrefix + "mysql"
 
 // NeedAutoID checks whether the table needs backing up with an autoid.
 func NeedAutoID(tblInfo *model.TableInfo) bool {
@@ -96,6 +97,11 @@ func EncloseDBAndTable(database, table string) string {
 	return fmt.Sprintf("%s.%s", EncloseName(database), EncloseName(table))
 }
 
+// IsTemplateSysDB checks wheterh the dbname is temporary system database(__TiDB_BR_Temporary_mysql).
+func IsTemplateSysDB(dbname model.CIStr) bool {
+	return dbname.O == temporarySysDB
+}
+
 // IsSysDB tests whether the database is system DB.
 // Currently, the only system DB is mysql.
 func IsSysDB(dbLowerName string) bool {

br/tests/br_backup_empty/run.sh

@@ -67,6 +67,7 @@ run_sql "CREATE TABLE ${DB}1.usertable1 ( \
   PRIMARY KEY (YCSB_KEY) \
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;"
 
+# backup empty table
 echo "backup empty table start..."
 run_br --pd $PD_ADDR backup full -s "local://$TEST_DIR/empty_table"
 
@@ -75,6 +76,7 @@ while [ $i -le $DB_COUNT ]; do
     i=$(($i+1))
 done
 
+# restore empty table.
 echo "restore empty table start..."
 run_br --pd $PD_ADDR restore full -s "local://$TEST_DIR/empty_table"
 
@@ -85,3 +87,15 @@ while [ $i -le $DB_COUNT ]; do
     run_sql "DROP DATABASE $DB$i;"
     i=$(($i+1))
 done
+
+
+# backup, skip temporary system database(__TiDB_BR_Temporary_mysql) when backup
+run_sql "CREATE DATABASE __TiDB_BR_Temporary_mysql";
+run_sql "CREATE TABLE __TiDB_BR_Temporary_mysql.tables_priv(id int);";
+echo "backup and skip __TiDB_BR_Temporary_mysql start..."
+run_br --pd $PD_ADDR backup full -s "local://$TEST_DIR/skip_temporary_mysql"
+
+# restore successfully without panic.
+run_sql "DROP DATABASE __TiDB_BR_Temporary_mysql";
+echo "restore the data start..."
+run_br restore full -s "local://$TEST_DIR/skip_temporary_mysql" --pd $PD_ADDR --ratelimit 1024