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Command: Exists

Checks whether a key with persistent durability exists. Use it instead of get when you only need to know whether the key is there: it does not return the value to the client, so it is cheaper, especially for large values.

Persistent keys are replicated and survive node failures. If the key does not exist, false is returned. For keys written with eset, use eexists.

Syntax​

exists <key>
exists <key> at <revision>
exists <key> as of <hlc-timestamp>
let <variable> = exists <key> [at <revision> | as of <hlc-timestamp>]

<revision> is an integer literal, and @ is a short form of at. See Get Revision.

Examples​

exists `config/limits/max-connections`
r- not exists 9ms
set `config/limits/max-connections` 1000
r0 set 11ms
exists `config/limits/max-connections`
r0 exists 8ms

Inside a script, assign the result to a variable:

let exists_key = exists "user:123:profile"
if exists_key then
  return "User found"
else
  return "User not found"
end

Reading Past Versions​

exists also supports snapshot reads with as of (timestamp format):

exists `config/limits/max-connections` as of 1718392012345

This checks whether the key existed at that snapshot time, not whether it exists now. at <revision> checks one exact revision instead.

Checking the Result​

A successful existence check counts as found for not found, just as a successful get does. The guard remembers the last read even when a let or a write runs between that read and the guard. See Statement-Result Guards.