DECR

Introduction and Use Case(s)

The DECR command in Redis is used to decrement the value of a key by 1. It is commonly used for counters, such as tracking the number of remaining attempts in an application or managing stock levels in inventory systems.

Syntax

DECR key

Parameter Explanations

• key: The name of the key whose value you want to decrement. This key must hold a string that can be represented as an integer.

Return Values

• Integer: The value of the key after the decrement operation.

Examples:

If the key does not exist, it is set to 0 before performing the operation.

Code Examples

dragonfly> SET counter 10
OK
dragonfly> DECR counter
(integer) 9
dragonfly> DECR counter
(integer) 8
dragonfly> GET counter
"8"
dragonfly> DECR non_existent_key
(integer) -1
dragonfly> GET non_existent_key
"-1"

Best Practices

• Ensure that the key holds a value that can be interpreted as an integer.
• When using DECR on keys that might not exist, design your application logic to handle cases where a missing key starts from 0.

Common Mistakes

• Using DECR on a key holding non-integer values will cause an error.
• Assuming DECR will only work on pre-existing keys; if the key does not exist, Redis initializes it to 0 and then decrements it.

FAQs

What happens if I use DECR on a key that contains a string?

An error will be returned because DECR expects the key to contain an integer value.

Can DECR create a key if it doesn’t exist?

Yes, if the key does not exist, Redis will create the key with a value of 0 and then perform the decrement operation.