Lua script syntax in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of using Lua scripts in Redis?

Lua scripts in Redis allow you to run multiple commands atomically and efficiently on the server side, reducing network overhead and ensuring data consistency.

beginner

How do you start a Lua script in Redis?

You start a Lua script in Redis by using the EVAL command followed by the Lua code as a string, the number of keys, and the keys and arguments.

beginner

In Redis Lua scripts, how do you access the keys and arguments passed to the script?

Keys are accessed using the global table KEYS (e.g., KEYS[1]), and arguments are accessed using the global table ARGV (e.g., ARGV[1]).

beginner

What does the following Lua script do in Redis?

return redis.call('GET', KEYS[1])

This script returns the value of the key passed as the first key argument to the script by calling the Redis GET command.

intermediate

How do you return multiple values from a Lua script in Redis?

You return multiple values by returning a Lua table (array) with the values, for example:

return {value1, value2}

. Redis converts this to a multi-bulk reply.

Which command is used to run a Lua script in Redis?

A RUN

B EXEC

C EVAL

D SCRIPT

The EVAL command runs Lua scripts in Redis.

In a Redis Lua script, how do you access the first key passed to the script?

A KEYS[1]

B KEYS[0]

C ARGV[1]

D ARGV[0]

Keys are accessed via KEYS table starting at index 1.

What does redis.call('SET', KEYS[1], ARGV[1]) do in a Lua script?

A Deletes a key

B Increments a key

C Gets the value of a key

D Sets the value of a key

It sets the value of the key KEYS[1] to the value ARGV[1].

What type of value should a Lua script return to send multiple values back to Redis?

A A number

B A Lua table (array)

C A string

D A boolean

Returning a Lua table sends multiple values as a multi-bulk reply.

Which of the following is true about Lua scripts in Redis?

A They run atomically

B They require restarting Redis

C They cannot access Redis commands

D They run asynchronously

Lua scripts run atomically in Redis, ensuring no other commands run during their execution.

Explain how to write and run a simple Lua script in Redis that gets the value of a key.

Think about how Redis passes keys and how Lua calls Redis commands.

Describe how Lua scripts in Redis handle multiple keys and arguments and how you access them inside the script.

Remember KEYS and ARGV are global tables in Lua scripts.