Data type: Hash hash data types

Hash hash data types

A definition of

1, a key field and an associated value for the composition
2, and the value field is a string
3, a hash can contain up to 2 ^ 32-1 key-value pairs

Two advantages

1, save memory space
2, each create a key, it will store some additional administrative information for this key (for example, type the key and time the key was last accessed)
more than three, key, redis database storage accessories consuming aspects of managing information more memory, CPU spent on key management database will be more

Three shortcomings (not suitable hash case)

1, using the bit operation command: SETBIT, GETBIT, BITCOUNT other, if you want to use these operations, the key string only
2, using an expired key function: the function keys only for expiration expired key operation, and the hash can not the fields expiring

Four basic commands Operation

# 1, a single field 
　　HSET Key Field value 
　　HSETNX value Key Field 
# 2, a plurality of fields 
　　HMSET value Key Field Field value
 # . 3, returns the number of fields 
　　HLEN Key
 # . 4, determines whether there is a field (absence returns 0) 
　　HEXISTS field Key
 # . 5, return to the field value 
　　HGET Key field
 # . 6, the plurality of field values returned 
　　HMGET Filed Key field
 # . 7, all the value pairs returned 
　　HGETALL Key
 # . 8, to return all the field names 
　　HKEYS Key
 # . 9, returns all values 
　　HVALS Key
 # 10, to delete the specified field 
　　the HDEL Key field 
 # . 11, for operation on the integer incremental values of the corresponding field 
　　HINCRBY Filed iNCREMENT Key
 # 12 is, perform floating-point arithmetic on the field corresponding to the incremental value
　　HINCRBYFLOAT key field increment

Five basic methods python

# 1, an update of the attribute data, not the new 
    HSET (name, Key, value) 
 # 2, this attribute specifies the read data, returns the string type 
    hget (name, Key)
 # . 3, batch update data (not the New) attribute parameter dictionary 
    hmset (name, Mapping)
 # . 4, the batch read data (not the new) property 
    hmget (name, Keys)
 # . 5, all the attributes and obtaining a value corresponding to this data, a Dictionary type 
    hgetall (name)
 # 6, get all the attribute names of this data, returns a list of types 
    hkeys (name)
 # 7, delete the specified attribute this data 
    hdel (name, * keys)

python code hash hash

Import Redis 

R & lt = redis.Redis (Host = " 192.168.153.136 " , Port = 6379, DB = 0)
 # Create a key named "user1" data comprising attribute name 
r.hset ( " user1 " , " name " , ' zhanshen001 ' )
 # change data key named "userinfo", changing the value of the property username 
r.hset ( " user1 " , " name " , ' zhanshen002 ' ) 

# extracted attribute value username 
username = r.hget ( "user1", "name")

# 输出看一下
print('name',username)

# 属性集合
user_dict = {
    "password": "123456",
    "name": "Wang Success",
    "sex": "male",
    "height": '178',
    "Tel": '13838383888 ' , 
} 
# add bulk properties 
r.hmset ( " user1 " , user_dict)
 # remove all data (return value Dictionary) 
all_data = r.hgetall ( " UserInfo " )
 Print ( ' all_data: ' , all_data)
 # Delete Attribute (you can bulk delete) 
r.hdel ( " user1 " , " Tel " )
 # remove all attribute names: list 
h_keys = r.hkeys ( " user1 " )
 Print ( ' all_key_name: ', h_keys)
 # remove all attribute values: List 
h_values = r.hvals ( ' user1 ' )
 Print ( ' all_values: ' , h_values)

Scenarios: redis + mysql + hash combination

principle:

　　Users want access to personal information
　　1, redis cache to access their personal information
　　2, redis not query, mysql to query and caching to redis
　　3, access to personal information again

Import redis
 Import pymysql 

# . 1, redis to query the personal information 
# 2, not redis query, the query to mysql, and cached to redis 
# . 3, access to personal information again 


R & lt = Host redis.Redis (= ' 192.168.153.136 ' , Port = 6379, DB = 0) 

username = iNPUT ( ' enter username: ' )
 # If no cache redis, empty dictionary is returned} { 
Result = r.hgetall (username)
 Print ( ' redis found: ' , the Result) 

# MySQL table fields: username, password, Gender, Age 
IF  not the Result: 
    db = pymysql.connect ('172.0.0.1','root','123456','spider',charset='utf8')
    cursor = db.cursor()
    cursor.execute('select gender,age from user where username=%s',[username])
    # (('m',30),)
    userinfo = cursor.fetchall()
    if not userinfo:
        print('MySQL中用户信息不存在')
    else:
        dict = {
             ' Gender ' : UserInfo [0] [0],
             ' Age ' : UserInfo [0] [. 1 ] 
        } 
        # hmset second parameter dictionary 
        r.hmset (username, dict)
         # set the expiration time of 5 min 
        r .expire (username, 60 *. 5 )
         Print ( ' Redis of cache hits ' )

Mysql database data updated cache information synchronized to redis

Import redis
 Import pymysql 


# after update data (mysql), synchronized to the buffer redis 


DEF update_mysql (Age, username): 
  DB = pymysql.connect ( ' 127.0.0.1 ' , ' the root ' , ' 123456 ' , ' the userdb ' , charset = ' UTF8 ' ) 
  Cursor = db.cursor () 
  UPD = ' Update User SET WHERE Age =% S% S = username ' 
  the try :
     # code: 0 or. 1 
    code = cursor.execute(upd, [age, username])
    db.commit()
    if code == 1:
      return True
  except Exception as e:
    db.rollback()
    print(e)
  cursor.close()
  db.close()

def update_redis(age):
  r = redis.Redis(host="127.0.0.1", port=6379, db=0)
  r.hset('user', 'age', age)
  print('已同步至redis')
  # 设置过期时间
  r.expire('User ' , 30 )
   # Test 
  Print (r.hget ( ' User ' , ' Age ' )) 


IF  the __name__ == ' __main__ ' : 
  username = INPUT ( ' Enter Username: ' ) 
  Age = INPUT ( ' Enter more the age-: ' )
   IF update_mysql (Age, username): 
    update_redis (Age) 
  the else :
     Print ( " user name is incorrect " )