Hlen

HLEN

1. 如果hash表存在且有字段，则返回字段的数量
2. 如果hash表没有字段，或者key不存在，则返回0

值得一提的是，当hash表没有字段时，exists命令返回的是0。也就相当于这个hash表已经不存在了。所以在上面的第二点中，均是返回0。

Command

$ redis-cli.exe -h 127.0.0.1 -p 6379
127.0.0.1:6379> hset snake name kobe
(integer) 1
127.0.0.1:6379> hlen snake
(integer) 1
127.0.0.1:6379> hdel snake name
(integer) 1
127.0.0.1:6379> hlen snake
(integer) 0
127.0.0.1:6379> exists fakeKey
(integer) 0
127.0.0.1:6379> hlen fakeKey
(integer) 0

Code

func Hlen(c redis.Conn) {
    defer c.Do("DEL", "snake")
    //  If hash table is existing and has field(s), will return the number of fields.
    c.Do("HSET", "snake", "name", "kobe")
    lengthOfTable, err := c.Do("HLEN", "snake")
    if err != nil {
        colorlog.Error(err.Error())
        return
    }
    fmt.Println("If hash table is existing, will return the number of fields:", lengthOfTable)
    //  if no fields in hash table, it will return 0. But if key doesn't exist, it still returns 0.
    //  Make hash table null at first for test.
    c.Do("HDEL", "snake", "name")
    lengthOfTable, err = c.Do("HLEN", "snake")
    if err != nil {
        colorlog.Error(err.Error())
    }
    fmt.Println("If hash table doesn't have any fields, will return:", lengthOfTable)
    //  If key doesn't exist, will return 0.
    isExist, _ := c.Do("EXISTS", "fakeKey")
    if isExist == 1 {
        c.Do("DEL", "fakeKey")
    }
    lengthOfTable, err = c.Do("HLEN", "fakeKey")
    if err != nil {
        colorlog.Error(err.Error())
    }
    fmt.Println("If key doesn't exist, will return:", lengthOfTable)
}

Ouput

$ go run main.go
If hash table is existing, will return the number of fields: 1
If hash table doesn't have any fields, will return: 0
If key doesn't exist, will return: 0