EXEC to execute in Redis - Step-by-Step Execution

Concept Flow - EXEC to execute

Start Transaction with MULTI

↓

Queue Commands

↓

Call EXEC

↓

Execute All Queued Commands

↓

Return Array of Results

↓

End

This flow shows how Redis queues commands after MULTI and executes them all at once when EXEC is called.

Execution Sample

Redis

MULTI
SET key1 "Hello"
INCR counter
EXEC

This code starts a transaction, queues two commands, then executes them together returning their results.

Execution Table

Step	Command	Action	Result	Notes
1	MULTI	Start transaction mode	OK	Commands will be queued, not executed immediately
2	SET key1 "Hello"	Queue command	QUEUED	Command added to transaction queue
3	INCR counter	Queue command	QUEUED	Command added to transaction queue
4	EXEC	Execute all queued commands	["OK", 1]	Returns results of SET and INCR commands
5	-	Transaction ends	-	All commands executed atomically

💡 EXEC runs all queued commands and returns their results, ending the transaction

Variable Tracker

Variable	Start	After MULTI	After SET queued	After INCR queued	After EXEC	Final
transaction_mode	off	on	on	on	off	off
command_queue	empty	empty	[SET key1 "Hello"]	[SET key1 "Hello", INCR counter]	empty	empty
key1	nil	nil	nil	nil	"Hello"	"Hello"
counter	nil	nil	nil	nil	1	1

Key Moments - 3 Insights

Why don't the SET and INCR commands run immediately after MULTI?

Because after MULTI, commands are queued and not executed until EXEC is called, as shown in execution_table rows 2 and 3 where commands return QUEUED.

What does EXEC return after running the queued commands?

EXEC returns an array with the results of each command in order, as seen in execution_table row 4 returning ["OK", 1].

What happens to the transaction mode after EXEC?

Transaction mode ends and command queue clears, shown in variable_tracker where transaction_mode goes from 'on' to 'off' and command_queue becomes empty after EXEC.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of the INCR command after EXEC?

A OK

B QUEUED

C 1

D nil

💡 Hint

Check the EXEC step in execution_table row 4 where the results array shows the INCR command result as 1.

At which step does the transaction mode turn off?

A After MULTI

B After EXEC

C After SET command

D After INCR command

💡 Hint

Look at variable_tracker for transaction_mode changes; it turns off after EXEC.

If you add another command after EXEC without MULTI, what happens?

A It executes immediately

B It queues the command

C It returns an error

D It ignores the command

💡 Hint

Recall that transaction_mode is off after EXEC, so commands run immediately, not queued.

Concept Snapshot

MULTI starts a transaction, queuing commands.
Commands return QUEUED until EXEC.
EXEC runs all queued commands atomically.
EXEC returns an array of results.
Transaction ends after EXEC.

Full Transcript

In Redis, the EXEC command executes all commands queued after MULTI. When you start a transaction with MULTI, commands like SET or INCR are not run immediately but queued. Each queued command returns QUEUED. When EXEC is called, Redis runs all queued commands in order and returns their results as an array. After EXEC, the transaction mode ends and commands run normally again. This ensures atomic execution of multiple commands.