How to Set Multiple Strings in Redis

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Redis provides us with a convenient way to set multiple strings at once. Specifically, the MSET command enables us to set multiple strings in one go.

There’s also the MSETNX command which does the same thing, but only if none of the keys already exist.

Example

Here’s an example of using the MSET command to set multiple strings:

MSET firstname "Rob" lastname "Banks" age 28

Result:

OK

This returns OK which means that all keys were set successfully.

We can use the MGET command to check their values:

MGET firstname lastname age

Result:

1) "Rob"
2) "Banks"
3) "28"

Overwrite Existing Keys

If one or more keys already exist, MSET replaces existing values with new values.

For example, we can set one or more of the above keys with new values:

MSET firstname "Rob" lastname "Bery" age 29

Result:

OK

Check the result:

MGET firstname lastname age

Result:

1) "Rob"
2) "Bery"
3) "29"

Don’t Overwrite Existing Keys

Sometimes we might not want to overwrite any keys if they already exist. In such cases, we can use the MSETNX command. With this command, the operation fails if any of the keys already exist.

For example:

MSETNX user "Chax" age 30

Result:

(integer) 0

In this case we get an integer reply of 0, which means that nothing was set. That’s because at least one of the keys already exists. In our case, the age key already exists (because we created it in the earlier examples).

This prevents us from accidentally overwriting something that we shouldn’t.

If we delete the age key and try again, we’ll be successful:

DEL age

Result:

(integer) 1

An integer reply of 1 means that it was successfully deleted.

Now let’s try running MSETNX again:

MSETNX user "Chax" age 30

Result:

(integer) 1

This time we get an integer reply of 1, which means that it was successful.

Let’s check the values:

MGET user age

Result:

1) "Chax"
2) "30"

Setting Timeouts, etc

If we need to set extra attributes for the keys, such as timeouts, we’ll need to use another approach.

Probably the most logical approach is to use the SET command. This command accepts arguments for things like timeouts and whether or not to overwrite the key if it exists, etc.

The downside is that we can only set one key at a time.

Therefore, we could use the following to set one of the above keys, only if it doesn’t exist:

SET user "Chax" NX EX 60

Result:

(nil)

In this case, nothing was set, because the key already exists. The NX argument specifies that the key can only be set if it doesn’t already exist. The EX argument allows us to specify a timeout in seconds.

But as mentioned, if we have multiple keys to set, we would need to run multiple calls to SET, one for each key we need to set. For example, here’s one for the age key:

SET age 31 GET KEEPTTL

Result:

"30"

In this case, I didn’t specify NX, so the key was overwritten with the new value. I also used the GET argument to return the old value of the key. And I used the KEEPTTL option to keep any timeouts as they are.

Here’s the new value:

GET age

Result:

"31"