[logutil]: Fix MaxDays and MaxBackups not working for slow-query-…

…logger (#27625) (#30171)

ref #25716

util/logutil/slow_query_logger.go

@@ -15,17 +15,15 @@ var _pool = buffer.NewPool()
 
 func newSlowQueryLogger(cfg *LogConfig) (*zap.Logger, *log.ZapProperties, error) {
 
- // copy global config and override slow query log file
- // if slow query log filename is empty, slow query log will behave the same as global log
+ // copy the global log config to slow log config
+ // if the filename of slow log config is empty, slow log will behave the same as global log.
  sqConfig := cfg.Config
  // level of the global log config doesn't affect the slow query logger which determines whether to
  // log by execution duration.
  sqConfig.Level = LogConfig{}.Level
  if len(cfg.SlowQueryFile) != 0 {
- sqConfig.File = log.FileLogConfig{
- MaxSize: cfg.File.MaxSize,
- Filename: cfg.SlowQueryFile,
- }
+ sqConfig.File = cfg.File
+ sqConfig.File.Filename = cfg.SlowQueryFile
  }
 
  // create the slow query logger