Script loading and caching in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to load a Lua script into Redis and get its SHA1 hash.

Redis

sha1 = redis.call('SCRIPT', '[1]', script)

Drag options to blanks, or click blank then click option'

ALOAD

BEXECUTE

CRUN

DEVAL

Attempts:

3 left

💡 Hint

Common Mistakes

Using EVAL instead of LOAD to get the SHA1 hash.

Using EXECUTE which is not a Redis command.

Confusing RUN with the correct command.

The LOAD command loads a Lua script into Redis and returns its SHA1 hash.

2fill in blank

medium

Complete the code to execute a cached Lua script by its SHA1 hash.

Redis

result = redis.call('[1]', sha1, 0)

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AEVALSHA

BLOAD

CEXECUTE

DRUN

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOAD instead of EVALSHA to execute the script.

Using EXECUTE which is not a Redis command.

Using RUN which is not a Redis command.

The EVALSHA command executes a cached Lua script by its SHA1 hash.

3fill in blank

hard

Fix the error in the code to check if a script is cached before running it.

Redis

if redis.call('SCRIPT', '[1]', sha1) == 1 then
    redis.call('EVALSHA', sha1, 0)
else
    sha1 = redis.call('SCRIPT', 'LOAD', script)
    redis.call('EVALSHA', sha1, 0)
end

Drag options to blanks, or click blank then click option'

AEXECUTE

BLOAD

CRUN

DEXISTS

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOAD to check existence instead of EXISTS.

Using RUN or EXECUTE which are not Redis commands.

Confusing SCRIPT LOAD with SCRIPT EXISTS.

The SCRIPT EXISTS command checks if a script is cached by its SHA1 hash.

4fill in blank

hard

Fill both blanks to load a script only if it is not cached, then execute it.

Redis

if redis.call('SCRIPT', '[1]', sha1) == 0 then
    sha1 = redis.call('SCRIPT', '[2]', script)
end
redis.call('EVALSHA', sha1, 0)

Drag options to blanks, or click blank then click option'

AEXISTS

BLOAD

CRUN

DEXECUTE

Attempts:

3 left

💡 Hint

Common Mistakes

Using LOAD to check existence.

Using RUN or EXECUTE commands which do not exist.

Not updating the sha1 variable after loading.

Use SCRIPT EXISTS to check if the script is cached, and SCRIPT LOAD to load it if not.

5fill in blank

hard

Fill all three blanks to cache a script, check its existence, and execute it safely.

Redis

sha1 = redis.call('SCRIPT', '[1]', script)
if redis.call('SCRIPT', '[2]', sha1) == 1 then
    redis.call('[3]', sha1, 0)
else
    redis.call('EVAL', script, 0)
end

Drag options to blanks, or click blank then click option'

ALOAD

BEXISTS

CEVALSHA

DRUN

Attempts:

3 left

💡 Hint

Common Mistakes

Using RUN which is not a Redis command.

Using EVAL instead of EVALSHA to run cached script.

Not checking if the script exists before running.

First, SCRIPT LOAD caches the script and returns its SHA1. Then SCRIPT EXISTS checks if it is cached. If yes, EVALSHA runs the cached script safely.