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Use HSETNX to set a hash field only when it does not already exist. The reply is 1 when the field was created and 0 when it was already present and left untouched. The check and the write happen atomically, so of several clients racing to fill the same field exactly one succeeds, which makes the command a way to claim a slot inside a hash without overwriting whatever a concurrent writer put there.

Syntax

Arguments

Response

The reply reports the result of the operation. Error replies have the same shape in RESP2 and RESP3 and are surfaced as exceptions by the SDKs below.
Client libraries often decode bulk strings, maps, sets, and numeric strings into language-native values. The table describes the Redis wire reply.

Examples

TCP examples use the TLS REDIS_URL from the Upstash console. REST examples use UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN.

Related topics

HSETNXOverview