diff --git a/model/t_uid/t_uid.go b/model/t_uid/t_uid.go
index e9d0bc6..146790c 100644
--- a/model/t_uid/t_uid.go
+++ b/model/t_uid/t_uid.go
@@ -18,6 +18,7 @@ type t_uid struct {
 	F_range_length int       `gorm:"column:F_range_length"`  // ID范围的长度
 	F_range_owner  string    `gorm:"column:F_range_owner"`   // ID范围的拥有者，一般是机器id
 	F_create_time  time.Time `gorm:"column:F_create_time"`   // 记录创建时间
+	F_modify_time  time.Time `gorm:"column:F_modify_time"`   // 记录更新时间
 }
 
 type typeInfo struct {
@@ -46,11 +47,15 @@ func (id *t_uid) TableName() string {
 }
 
 func (id *t_uid) BeforeCreate(db *gorm.DB) error {
-	id.F_create_time = time.Now()
+	if id.F_create_time.IsZero() {
+		id.F_create_time = time.Now()
+		id.F_modify_time = time.Now()
+	}
 	return nil
 }
 
 func (id *t_uid) BeforeUpdate(db *gorm.DB) (err error) {
+	id.F_modify_time = time.Now()
 	return nil
 }
 
diff --git a/uid.go b/uid.go
index cb1c305..274d3a4 100644
--- a/uid.go
+++ b/uid.go
@@ -206,7 +206,21 @@ func (idg *idCreator) createNewRange(prefix string) error {
 
 func (idg *idCreator) getCurrentRange(prefix string) (r *Range) {
 	// Step 0. get ranges queue by prefix.
-	var queue, ok = idg.Ranges[prefix]
+	var (
+		trycount             = 0
+		queue    *rangeQueue = nil
+		ok                   = false
+	)
+	for trycount = 0; !ok && trycount < 3; trycount++ {
+		if queue, ok = idg.Ranges[prefix]; !ok {
+			idg.createNewRange(prefix)
+		}
+	}
+	if !ok {
+		panic("maybe something bug, cannot found range queue after createNewRange")
+	}
+
+	queue, ok = idg.Ranges[prefix]
 	if !ok {
 		idg.createNewRange(prefix)
 	}