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WATCH

Last updated 
WATCH key [key ...]
Group
Transactions
Complexity
O(1) per key
Arity
-2 (at least 2 words, counting the command name)
Flags
fast
Keys
first 1, last final argument, step 1
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WATCH marks keys for optimistic locking. If any watched key is modified by another client, deleted, or expires before your EXEC, the transaction is not run and EXEC replies with a null. This lets you read values, decide what to write, and apply the writes only if nothing changed in between, retrying otherwise.

Watched keys are unwatched by EXEC, DISCARD and UNWATCH, and when the connection closes. Watching a key that is already watched keeps its original state. Watching a key is not an access to it.

WATCH must be sent before MULTI.

Return value

Section titled “Return value”
Case RESP2 RESP3
Always Simple string OK Simple string OK
Inside a transaction Error ERR WATCH inside MULTI is not allowed Error

Examples

Section titled “Examples”
127.0.0.1:6379> SET balance 100
OK
127.0.0.1:6379> WATCH balance
OK
127.0.0.1:6379> GET balance
"100"
127.0.0.1:6379> MULTI
OK
127.0.0.1:6379(TX)> DECRBY balance 30
QUEUED
127.0.0.1:6379(TX)> EXEC
1) (integer) 70

Compatibility

Section titled “Compatibility”

Same as Redis 7 and Valkey 8.

See also

Section titled “See also”

UNWATCH, MULTI, EXEC