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MEMORY USAGE

Last updated 
MEMORY USAGE key [SAMPLES count]
Group
Server
Complexity
O(N) where N is the number of elements sampled
Arity
-3 (at least 3 words, counting the command name)
HotKV Cloud
All plans
On-Premise
no license needed

MEMORY USAGE estimates the memory a key uses, including its name, its value and the bookkeeping around them. Use it to find out which keys are worth shrinking, or to estimate the memory a data set will need.

For collections (lists, sets, hashes, sorted sets, streams), measuring every element of a large value would be slow, so by default the first 5 elements are measured and the rest are assumed to be the same size. Pass SAMPLES to change that.

Looking a key up with MEMORY USAGE does not count as an access: it does not change the key’s last access time and is not counted as a hit or a miss.

Options

Section titled “Options”
Option Effect
SAMPLES count Measure this many elements of a collection. 0 measures all of them.

Return value

Section titled “Return value”
Case RESP2 RESP3
Key exists Integer: estimated bytes Integer
Key does not exist Nil bulk string Null

Errors: ERR syntax error for an option other than SAMPLES, a missing count, or a negative count; ERR value is not an integer or out of range for a count that is not an integer.

Examples

Section titled “Examples”
127.0.0.1:6379> SET greeting "hello"
OK
127.0.0.1:6379> MEMORY USAGE greeting
(integer) 56
127.0.0.1:6379> MEMORY USAGE big:hash SAMPLES 0
(integer) 1843224
127.0.0.1:6379> MEMORY USAGE nosuchkey
(nil)

The numbers are estimates; they depend on the data and the HotKV version.

Compatibility

Section titled “Compatibility”

Same syntax, sampling default and replies as Redis 7 and Valkey 8.

See also

Section titled “See also”

MEMORY STATS, OBJECT ENCODING, STRLEN