GETRANGE and SETRANGE in Redis - Step-by-Step Execution

Concept Flow - GETRANGE and SETRANGE

Start with a string value

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Use SETRANGE to modify part of the string

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Use GETRANGE to extract substring

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Return modified string or substring

You start with a string stored in Redis, then use SETRANGE to change part of it, and GETRANGE to get a substring from it.

Execution Sample

Redis

SET mykey "Hello World"
SETRANGE mykey 6 "Redis"
GETRANGE mykey 0 10

Set a string, replace part starting at position 6, then get substring from 0 to 10.

Execution Table

Step	Command	Input String	Action	Result String	Output
1	SET mykey "Hello World"	N/A	Set key to 'Hello World'	Hello World	OK
2	SETRANGE mykey 6 "Redis"	Hello World	Replace from index 6 with 'Redis'	Hello Redis	11
3	GETRANGE mykey 0 10	Hello Redis	Get substring from 0 to 10	Hello Redis	Hello Redis
4	GETRANGE mykey 0 4	Hello Redis	Get substring from 0 to 4	Hello	Hello
5	SETRANGE mykey 11 "!"	Hello Redis	Extend string by adding '!' at index 11	Hello Redis!	12
6	GETRANGE mykey 0 11	Hello Redis!	Get substring from 0 to 11	Hello Redis!	Hello Redis!
7	GETRANGE mykey 12 15	Hello Redis!	Get substring beyond string length

💡 Commands complete; GETRANGE returns empty string when range is outside string length.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 5
mykey	N/A	Hello World	Hello Redis	Hello Redis!

Key Moments - 3 Insights

Why does SETRANGE change the string length when replacing beyond current length?

SETRANGE extends the string if the offset is beyond current length by padding with zero bytes, as shown in step 5 where adding '!' at index 11 extends 'Hello Redis' to 'Hello Redis!'.

What happens if GETRANGE requests a substring beyond the string's length?

GETRANGE returns an empty string if the requested range is outside the string length, as in step 7 where indices 12 to 15 return ''.

Does SETRANGE overwrite or insert the new substring?

SETRANGE overwrites existing characters starting at the offset without shifting the rest, as in step 2 where 'World' is replaced by 'Redis' starting at index 6.

Visual Quiz - 3 Questions

Look at the execution table, what is the string value of 'mykey' after step 2?

A "Hello Redis!"

B "Hello World"

C "Hello Redis"

D "Redis World"

💡 Hint

Check the 'Result String' column in row for step 2.

At which step does the string 'mykey' get extended beyond its original length?

A Step 5

B Step 2

C Step 3

D Step 7

💡 Hint

Look for when the 'Result String' length increases beyond 'Hello Redis'.

If GETRANGE is called with start=12 and end=15 on 'Hello Redis!', what is the output?

A "Redis"

B "" (empty string)

C "!"

D "Hello"

💡 Hint

See step 7 in the execution table for GETRANGE beyond string length.

Concept Snapshot

GETRANGE key start end
- Returns substring from start to end (inclusive).
- Indices start at 0.

SETRANGE key offset value
- Overwrites string starting at offset with value.
- Extends string if offset beyond current length.
- Returns new string length.

Full Transcript

This visual execution trace shows how Redis commands GETRANGE and SETRANGE work on string values. First, a string 'Hello World' is set. Then SETRANGE replaces part of the string starting at index 6 with 'Redis', changing it to 'Hello Redis'. GETRANGE extracts substrings by specifying start and end indices, returning parts like 'Hello Redis' or 'Hello'. SETRANGE can also extend the string if the offset is beyond the current length, as when adding '!' at index 11. GETRANGE returns an empty string if the requested range is outside the string length. These steps help understand how to modify and read parts of strings stored in Redis.