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Redis HSTRLEN in Ruby (Detailed Guide w/ Code Examples)

Use Case(s)

The HSTRLEN command in Redis is used when we want to retrieve the length of the value of a hash field. This command is useful when developing applications that require a check on the length of stored data without retrieving the entire value, such as limiting text input or monitoring data size.

Code Examples

Let's assume you're using the redis gem in Ruby. Here's an example usage of the HSTRLEN command:

require 'redis' redis = # Set a hash redis.hset("myhash", "field1", "Hello World") # Get length of the value of a hash field length = redis.hstrlen("myhash", "field1") puts length # Output: 11

In this example, we first create a new Redis object. Then, we set a hash with the key myhash and a field field1 with the value Hello World. Lastly, we use hstrlen to get the length of the value of field1, which is 11 ('Hello World' is 11 characters long).

Best Practices

  • It's recommended to check if a hash field exists before calling HSTRLEN to prevent unnecessary exceptions.
  • Use HSTRLEN sparingly in performance-critical parts of your code, as it might result in additional round trips to the server if not used in conjunction with other commands.

Common Mistakes

  • Misunderstanding that HSTRLEN returns the length of the string value, not the count of hash fields or their keys.
  • Assuming that HSTRLEN will return zero for non-existing keys or fields. In reality, it returns nil.


Q: What does HSTRLEN return if the key or field does not exist? A: The HSTRLEN command will return nil if the key or the field does not exist.

Q: Does the HSTRLEN command change any data in Redis? A: No, the HSTRLEN command is a read-only command and does not modify any data stored in Redis.

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