EVALSHA for cached scripts in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run a cached Lua script using its SHA1 hash.

Redis

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

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AEVAL

BEVALSHA

CSCRIPT LOAD

DGET

Attempts:

3 left

💡 Hint

Common Mistakes

Using EVAL instead of EVALSHA

Trying to use SCRIPT LOAD to run the script

Using GET which is unrelated

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

2fill in blank

medium

Complete the code to run a cached script with 2 keys and 1 argument.

Redis

redis.call('EVALSHA', sha1, [1], key1, key2, arg1)

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A0

B1

C3

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Counting arguments instead of keys

Using 3 instead of 2

Using 1 or 0 which is too few

The argument after SHA1 in EVALSHA is the number of keys; here there are 2 keys (key1, key2).

3fill in blank

hard

Fix the error in the code to correctly run a cached script with no keys.

Redis

redis.call('EVALSHA', sha1, [1])

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A0

B1

Cnil

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 when no keys are passed

Using nil or null which are invalid in Redis commands

When running EVALSHA with no keys, the number of keys argument must be 0.

4fill in blank

hard

Fill both blanks to load a script and then run it using EVALSHA.

Redis

local sha1 = redis.call('[1]', script)
redis.call('[2]', sha1, 0)

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ASCRIPT LOAD

BEVALSHA

CEVAL

DGET

Attempts:

3 left

💡 Hint

Common Mistakes

Using EVAL instead of SCRIPT LOAD to cache

Using SCRIPT LOAD instead of EVALSHA to run

Using GET which is unrelated

First, SCRIPT LOAD caches the script and returns its SHA1. Then EVALSHA runs the cached script by SHA1.

5fill in blank

hard

Fill all three blanks to load a script, then run it with 1 key and 2 arguments.

Redis

local sha1 = redis.call('[1]', script)
redis.call('[2]', sha1, [3], key1, arg1, arg2)

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

ASCRIPT LOAD

BEVALSHA

C1

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using 2 instead of 1 for number of keys

Using EVAL instead of EVALSHA to run

Using wrong commands to load script

SCRIPT LOAD caches the script and returns SHA1. EVALSHA runs it. The number 1 means one key is passed.