OBJECT ENCODING for internal encoding in Redis - Step-by-Step Execution

Concept Flow - OBJECT ENCODING for internal encoding

Client sends command

↓

Redis receives object

↓

Check object type

↓

Choose internal encoding

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Store object with encoding

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Use encoding for operations

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Return result to client

Redis receives data, decides the best way to store it internally, then uses that encoding for fast operations.

Execution Sample

Redis

SET mykey "100"
GET mykey
INCR mykey

Store a string '100', retrieve it, then increment it as a number.

Execution Table

Step	Command	Object Type	Encoding Chosen	Action	Result
1	SET mykey "100"	String	INT	Store as integer encoding	OK
2	GET mykey	String	INT	Retrieve and convert to string	"100"
3	INCR mykey	String	INT	Increment integer value	101
4	GET mykey	String	INT	Retrieve updated value	"101"
5	SET mykey "Hello"	String	RAW	Store as raw string encoding	OK
6	GET mykey	String	RAW	Retrieve raw string	"Hello"
7	INCR mykey	String	RAW	Fail increment, not integer	ERROR: value is not an integer or out of range

💡 Execution stops after error on incrementing non-integer encoded string.

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 5	After Step 7
mykey	null	100 (INT encoding)	101 (INT encoding)	Hello (RAW encoding)	Hello (RAW encoding)

Key Moments - 3 Insights

Why does Redis store '100' as INT encoding instead of RAW string?

Redis detects the string '100' can be stored more efficiently as an integer (see Step 1 in execution_table), saving memory and speeding numeric operations.

What happens when we try to increment a key storing a non-integer string?

At Step 7, Redis returns an error because the encoding is RAW string, which cannot be incremented as a number.

Does Redis change encoding automatically when value changes type?

Yes, at Step 5, setting 'Hello' changes encoding from INT to RAW because 'Hello' is not a number.

Visual Quiz - 3 Questions

Look at the execution_table, what encoding does Redis use after storing '100'?

A RAW string encoding

B INT encoding

C HASH encoding

D ZIPLIST encoding

💡 Hint

Check Step 1 in execution_table under 'Encoding Chosen'

At which step does Redis return an error due to wrong encoding?

A Step 3

B Step 5

C Step 7

D Step 2

💡 Hint

Look for 'ERROR' in the Result column of execution_table

If we set mykey to '200' after Step 7, what encoding will Redis choose?

A INT encoding

B RAW string encoding

C HASH encoding

D LIST encoding

💡 Hint

Refer to Step 1 where '100' was stored as INT encoding

Concept Snapshot

Redis stores data internally using different encodings.
Strings like numbers can be stored as INT encoding for efficiency.
Non-numeric strings use RAW encoding.
Encoding affects performance and supported operations.
Redis switches encoding automatically based on value type.

Full Transcript

This visual execution shows how Redis encodes objects internally. When a client sets a key with a numeric string like '100', Redis stores it using integer encoding for efficiency. Retrieving and incrementing this key works smoothly. If the key is set to a non-numeric string like 'Hello', Redis switches to raw string encoding. Trying to increment a raw string causes an error. This demonstrates Redis's dynamic encoding choice based on the data type, optimizing memory and performance while enforcing operation rules.