1.7. Memcached replace command

发布时间 :2024-03-18 01:40:05 UTC      

Memcached replace command is used to replace the existing key value (data value).

If key does not exist, the replacement fails and you will get a response NOT_STORED .

1.7.1. Syntax:

The replace basic syntax format of the command is as follows:

replace key flags exptime bytes [noreply]
value

The parameters are described as follows:

  • key :Key value key-value in the structure key used to find cached values

  • flags :Can include integer parameters for key-value pairs, which clients use to store additional information about key-value pairs

  • exptime :Length of time to save key-value pairs in the cache (in seconds,0 means forever)

  • bytes :Number of bytes stored in the cache

  • noreply (optional): this parameter tells the server that there is no need to return data

  • value :The stored value (always in the second line) (which can be directly understood as key-value in the structure value )

1.7.2. Example

In the following example, we set:

  • Key → mykey

  • Flag → 0

  • Exptime → 900 (in seconds)

  • Bytes → 10 (bytes of data storage)

  • Value → data_value

In the following example, we use the key ‘mykey’’ and store the corresponding value data_value . After execution, we replace the same key the value of is ‘some_other_value’ .

add mykey 0 900 10
data_value
STORED
get mykey
VALUE mykey 0 10
data_value
END
replace mykey 0 900 16
some_other_value
get mykey
VALUE mykey 0 16
some_other_value
END

1.7.3. Output

If the data is added successfully, the output:

STORED

Output information description:

  • STORED :Output after being saved successfully

  • NOT_STORED :Output after failed to perform replacement

Principles, Technologies, and Methods of Geographic Information Systems  102

In recent years, Geographic Information Systems (GIS) have undergone rapid development in both theoretical and practical dimensions. GIS has been widely applied for modeling and decision-making support across various fields such as urban management, regional planning, and environmental remediation, establishing geographic information as a vital component of the information era. The introduction of the “Digital Earth” concept has further accelerated the advancement of GIS, which serves as its technical foundation. Concurrently, scholars have been dedicated to theoretical research in areas like spatial cognition, spatial data uncertainty, and the formalization of spatial relationships. This reflects the dual nature of GIS as both an applied technology and an academic discipline, with the two aspects forming a mutually reinforcing cycle of progress.