How to Use EXEC Command in Redis Transactions

In Redis, EXEC is used to execute all commands queued after a MULTI command atomically as a transaction. It runs all queued commands in order and returns their results together.

Syntax

The EXEC command is used after MULTI to execute all queued commands in a transaction. The basic flow is:

• MULTI: Start the transaction and queue commands.
• Queue commands: Commands are queued but not executed immediately.
• EXEC: Executes all queued commands atomically.

redis

MULTI
<command1>
<command2>
...
EXEC

Example

This example shows how to increment two keys atomically using MULTI and EXEC. Both increments happen together or not at all.

redis

127.0.0.1:6379> MULTI
OK
127.0.0.1:6379> INCR counter1
QUEUED
127.0.0.1:6379> INCR counter2
QUEUED
127.0.0.1:6379> EXEC
1) (integer) 1
2) (integer) 1

Output

1) (integer) 1
2) (integer) 1

Common Pitfalls

Common mistakes when using EXEC include:

• Forgetting to call MULTI before queuing commands, so EXEC has nothing to run.
• Not checking for errors in queued commands; EXEC runs all commands regardless of individual errors.
• Using WATCH without proper handling can cause EXEC to return null if keys were modified.

redis

127.0.0.1:6379> INCR counter1
(integer) 1
127.0.0.1:6379> EXEC
(error) ERR EXEC without MULTI

-- Correct way --
127.0.0.1:6379> MULTI
OK
127.0.0.1:6379> INCR counter1
QUEUED
127.0.0.1:6379> EXEC
1) (integer) 2

Output

(error) ERR EXEC without MULTI

1) (integer) 2

Quick Reference

Command	Description
MULTI	Start a transaction and queue commands
EXEC	Execute all queued commands atomically
DISCARD	Cancel the transaction and clear queued commands
WATCH	Monitor keys for changes to conditionally abort EXEC

Key Takeaways

Use MULTI to start queuing commands before EXEC runs them atomically.

EXEC executes all queued commands in order and returns their results together.

If EXEC is called without MULTI, Redis returns an error.

WATCH can be used to monitor keys and abort EXEC if keys change.

Always check EXEC's return to handle transaction success or failure.