If you’re getting an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when using the Redis HSTRLEN command, it’s probably because you’re running the command against a key that doesn’t contain a hash.

The HSTRLEN command is a hash command, and is only intended to be used against hashes.

To fix this issue, be sure to run the command against a key that stores a hash. Alternatively, if you intend to run it against a different key type, then use a command designed for that key type.

Example of Error

Here’s an example of code that causes the error:

HSTRLEN color rgb

Result:

(error) WRONGTYPE Operation against a key holding the wrong kind of value

In this case, the key holds a string (not a hash) and so we get the error.

We can verify this with the TYPE command:

TYPE color

Result:

string

Yes it’s a string. The HSTRLEN command doesn’t work on strings, which explains why we got the error.

To solve this issue, be sure to run the command against the correct key type.

Solution 1

If your intention is to run this against a hash, then make sure the key contains a hash:

HSTRLEN customer lastname

Result:

(integer) 7

In this case, I ran the command against a hash, and got the result I was looking for.

Solution 2

If your intention is to get the string length of a different data type, you’ll need to change to a more suitable command. The reason our color key caused the error above is because it contains a string instead of a hash. In this case, if we really wanted to return the length of the string in that key, then we should use the STRLEN command instead:

STRLEN color

Result:

(integer) 6

This time it worked for that key.

We can check the key’s value to verify this result:

GET color

Result:

"Yellow"

As expected, it has a string length of six.