The Redis HLEN command returns the number of fields in the hash stored at the specified key.
Category: NoSQL
Fix “WRONGTYPE Operation against a key holding the wrong kind of value” when using SMEMBERS in Redis
If you get an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when using the SMEMBERS command in Redis, it’s probably because you’re passing a key with the wrong data type to the command.
The SMEMBERS command is a “set” command, and so it is intended to be used on keys that contain a set. If the key holds a different data type, you’ll likely get the above error.
Redis HGETALL Command
The Redis HGETALL command returns all fields and values from the hash at the specified key.
Redis HMGET Command
The Redis HMGET command allows us to get multiple values from a hash. It returns the value/s associated with the specified field/s in the hash at the specified key.
Redis HGET Command
The Redis HGET command allows us to get a value from a hash. It returns the value associated with the specified field in the hash at the specified key.
Redis HRANDFIELD Command
The Redis HRANDFIELD command allows us to get a random field from a given key.
The command accepts several arguments that allows us to specify the number of random fields returned, whether to include the same field multiple times, and whether or not to include the values with each field returned.
The HRANDFIELD command was introduced in Redis 6.2.0.
Redis HEXISTS Command
In Redis, the HEXISTS command allows us to check whether a field exists in a given hash. We pass the name of the key and the field to the command, and it returns 1 if the field exists, and 0 if it doesn’t.
Fix “ERR numkeys should be greater than 0” when using the SINTERCARD Command in Redis
If you’re getting an error that reads “ERR numkeys should be greater than 0” in Redis, it’s probably because you’re specifying a wrong value for the first argument when calling the SINTERCARD command.
To fix this issue, make sure you’re passing a valid non-zero value that matches the number of keys you’re comparing.
Continue readingRedis HKEYS Command
The Redis HKEYS command returns all fields in the hash stored at the specified key.
Redis HDEL Command
In Redis, the HDEL command enables us to delete one or more fields in a hash. It deletes the specified field/s at the specified key.
If the field doesn’t exist, it’s ignored. If the key doesn’t exist, it’s treated as an empty hash and 0 is returned.