This topic describes the commands that you can run on ApsaraDB for Redis Enhanced Edition (Tair) instances to enhance the string function. These commands include Compare And Set (CAS) and Compare And Delete (CAD).
Prerequisites
The instance is a performance-enhanced or persistent memory-optimized instance of the ApsaraDB for Redis Enhanced Edition (Tair) whose minor version is 1.2.3 or later. For more information about performance-enhanced instances and persistent memory-optimized instances, see Performance-enhanced instances and Persistent memory-optimized instances. For more information about how to update the minor version, see Update the minor version.Precautions
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In this topic, the strings that you want to manage are native Redis strings.Note You can manage Redis strings and TairStrings on an ApsaraDB for Redis Enhanced Edition (Tair) instance. However, CAS and CAD commands are applicable only to Redis strings.
- Latest minor version provides more features and higher stability. We recommend that
you update the instance to the latest minor version.
Note If your instance is a cluster instance or read/write splitting instance, we recommend that you update the proxy nodes in the instance to the latest minor version to ensure that all commands can be run as expected. For more information about cluster instances and read/write splitting instances, see Cluster master-replica instances and Read/write splitting instances.
Supported commands
Command | Syntax | Description |
---|---|---|
CAS | CAS key oldvalue newvalue |
Changes the existing value of a specified key if the existing value matches a specified
one. Otherwise, the existing value remains unchanged.
Note This command applies only to Redis strings. To change TairString values, run the EXCAS
command.
|
CAD | CAD key value |
Deletes a specified key if the existing value of the key matches a specified one.
Otherwise, the key is not deleted.
Note This command applies only to Redis strings. To delete TairString keys, run the EXCAD
command.
|
Uppercase keyword
: the command keyword.Italic
: Words in italic indicate variable information that you supply.[options]
: optional parameters. Parameters that are not included in brackets are required.AB
: specifies that these parameters are mutually exclusive. Select one of two or more parameters....
: specifies to repeat the preceding content.
CAS
Item | Description |
---|---|
Syntax | CAS key oldvalue newvalue |
Time complexity | O(1) |
Command description |
Changes the existing value of a specified key if the existing value matches a specified
one. Otherwise, the existing value remains unchanged.
Note This command applies only to Redis strings. To change TairString values, run the EXCAS
command.
|
Parameter |
|
Output |
|
Example |
The Sample command:
Sample output:
If you run the |
CAD
Item | Description |
---|---|
Syntax | CAD key value |
Time complexity | O(1) |
Command description |
Deletes a specified key if the existing value of the key matches a specified one.
Otherwise, the key is not deleted.
Note This command applies only to Redis strings. To delete TairString keys, run the EXCAD
command.
|
Parameter |
|
Output |
|
Example |
The Sample command:
Sample output:
After this command is run, the foo key is deleted. Then, if you run the |