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EVAL_RO

Syntax​

EVAL_RO script numkeys [key [key ...]] [arg [arg ...]]

Time complexity: Depends on the script that is executed.

ACL categories: @slow, @scripting

Execute a server-side Lua script in read-only mode.

EVAL_RO is identical to EVAL, except that the script must not perform any write operations. Scripts executed via EVAL_RO are treated as read-only and may run with different transaction semantics.

The first argument is the script's source code. The second argument is the number of input key name arguments, followed by all the keys accessed by the script. Any additional input arguments should not represent names of keys.

For a general introduction to scripting, see EVAL and the Redis Programmability docs. For Valkey semantics reference, see the corresponding command page.

Return​

The reply is the result returned by the script, using the RESP types.

Examples​

dragonfly> SET mykey 1
dragonfly> EVAL_RO "return redis.call('GET', KEYS[1])" 1 mykey
"1"
dragonfly> SET mykey 1
dragonfly> EVAL_RO "redis.call('SET', KEYS[1], 'x'); return 1" 1 mykey
(error) ERR Error running script (call to 32c1c320503641a699eba3c8f1f16cacb98c3393): @user_script:2: Write commands are not allowed from read-only scripts

Notes​

  • EVAL_RO must not modify data. If a script attempts to call mutating commands (e.g., SET, HSET, LPUSH), the server returns an error.
  • Keys used by the script must be declared via numkeys and subsequent key arguments, same as EVAL.
  • Dragonfly enforces read-only behavior and may optimize execution accordingly.

See also​

EVAL | EVALSHA | EVALSHA_RO