DISCARD to abort in Redis - Step-by-Step Execution

Concept Flow - DISCARD to abort

Start Transaction with MULTI

↓

Queue Commands

↓

DECIDE to Abort?

↓

Run DISCARD

↓

Clear Queue

↓

End Transaction

This flow shows how a Redis transaction starts, queues commands, then either aborts with DISCARD or executes with EXEC.

Execution Sample

Redis

MULTI
SET key1 value1
SET key2 value2
DISCARD

Starts a transaction, queues two SET commands, then aborts all queued commands with DISCARD.

Execution Table

Step	Command	Action	Transaction Queue State	Output
1	MULTI	Start transaction	Empty queue	OK
2	SET key1 value1	Queue command	['SET key1 value1']	QUEUED
3	SET key2 value2	Queue command	['SET key1 value1', 'SET key2 value2']	QUEUED
4	DISCARD	Abort transaction and clear queue	Empty queue	OK
5	-	No commands executed	Empty queue	(nil)

💡 DISCARD clears the queued commands and ends the transaction without executing them.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	Final
Transaction Queue	Empty	Empty	['SET key1 value1']	['SET key1 value1', 'SET key2 value2']	Empty	Empty

Key Moments - 2 Insights

Why does DISCARD clear the queued commands instead of executing them?

DISCARD is designed to abort the transaction. As shown in execution_table step 4, it clears the queue so no commands run.

What happens if you run EXEC after DISCARD?

After DISCARD, the queue is empty (see variable_tracker final state), so EXEC would execute nothing and return nil.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the state of the transaction queue?

A Empty queue

B Contains one command

C Contains two commands

D Transaction ended

💡 Hint

Check the 'Transaction Queue State' column at step 3 in execution_table.

At which step does the transaction queue get cleared?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look for the step where DISCARD is run and queue becomes empty in execution_table.

If DISCARD was replaced by EXEC at step 4, what would happen?

A Queue would be cleared without execution

B Commands would be executed

C Transaction would abort

D Error would occur

💡 Hint

EXEC runs all queued commands; see concept_flow branch where No leads to EXEC.

Concept Snapshot

DISCARD aborts a Redis transaction.
Use MULTI to start queuing commands.
Commands are queued but not run until EXEC.
DISCARD clears the queue and ends the transaction.
No commands run after DISCARD.
Useful to cancel a transaction safely.

Full Transcript

In Redis, when you start a transaction with MULTI, commands are queued but not executed immediately. You can either execute all queued commands with EXEC or abort the transaction with DISCARD. DISCARD clears all queued commands and ends the transaction without running them. This is useful if you decide not to proceed with the transaction. The execution table shows starting MULTI, queuing two SET commands, then DISCARD clears the queue. The variable tracker confirms the queue is empty after DISCARD. If you run EXEC after DISCARD, nothing happens because the queue is empty. This flow helps you safely cancel transactions in Redis.