If you get an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when using the ZINTER command in Redis, it’s probably because you’re passing a key with the wrong data type.

To fix this issue, be sure that the key you pass to the ZINTER command holds a sorted set.

Example of Error

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

ZINCRBY country 3 Australia

Result:

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

Here the country key contains a string and so we get an error.

I get the same error when I run the code against a (non-sorted) set:

ZINCRBY countries 3 Australia

Result:

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

In this case the countries key holds a (non-sorted) set, and so we get the same error.

Solution

The solution is to make sure the key we pass contains the correct data type. The ZINCRBY command is designed to be used on sorted sets, so we should make sure the specified key contains a sorted set.

Here’s an example of running the command against a key that holds a sorted set:

ZINCRBY cats 3 meow

Result:

"4"

This time we didn’t get the error because the key holds a sorted set.

In this case, the member was incremented by 3, which resulted in it having a score of 4 (its original score was 1).

Check a Key’s Data Type

If you’re not sure whether or not a key contains a sorted set, you can use the TYPE command to check its data type:

TYPE country

Result:

string

This example confirms why we got the error earlier on. The country key contains a string instead of a sorted set.

Let’s check the countries key:

TYPE countries

Result:

set

The countries key contains a set, but it’s not a sorted set. That’s why we got the error when we passed it to the ZINCRBY command in the earlier example.