lightning: fix in-correctly check for session variable (#29291)

br/pkg/lightning/lightning.go

@@ -75,6 +75,9 @@ type Lightning struct {
 }
 
 func initEnv(cfg *config.GlobalConfig) error {
+	if cfg.App.Config.File == "" {
+		return nil
+	}
 	return log.InitLogger(&cfg.App.Config, cfg.TiDB.LogLevel)
 }
 

br/pkg/lightning/restore/table_restore.go

@@ -192,6 +192,7 @@ func createColumnPermutation(columns []string, ignoreColumns []string, tableInfo
 func (tr *TableRestore) restoreEngines(pCtx context.Context, rc *Controller, cp *checkpoints.TableCheckpoint) error {
 	indexEngineCp := cp.Engines[indexEngineID]
 	if indexEngineCp == nil {
+		tr.logger.Error("fail to restoreEngines because indexengine is nil")
 		return errors.Errorf("table %v index engine checkpoint not found", tr.tableName)
 	}
 	// If there is an index engine only, it indicates no data needs to restore.

br/pkg/lightning/restore/tidb.go

@@ -112,9 +112,10 @@ func DBFromConfig(ctx context.Context, dsn config.DBStore) (*sql.DB, error) {
 		// always set auto-commit to ON
 		"autocommit": "1",
 	}
+
 	if dsn.Vars != nil {
 		for k, v := range dsn.Vars {
-			param.Vars[k] = v
+			vars[k] = v
 		}
 	}