Redis HLEN command is used to fetch the number of fields contained in a hash. This becomes an important operation when you want to know the size of your hash data structure, particularly useful in cases where you are storing large amounts of key-value pairs within a single hash.
Let's start by connecting to the Redis server:
Assume we have a hash 'user:1000' with multiple field-value pairs:
Now, let's use HLEN to get the count of keys under this hash:
In the above example,
hlen method returned the count of fields in the hash 'user:1000'.
Q: What happens if I use HLEN on a key that doesn't exist?
A: If you use HLEN on a key that doesn't exist, Redis will return 0.
Q: What happens if I use HLEN on a key that is not a hash?
A: If you try to use HLEN on a data type other than a hash, it will return an error.