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description Learn how to use the CF.ADDNX command to add an item to a Cuckoo filter only if it does not already exist.

import PageTitle from '@site/src/components/PageTitle';

CF.ADDNX

Syntax

CF.ADDNX key item

Time complexity: O(k + i), where k is the number of sub-filters and i is MAXITERATIONS

ACL categories: @cuckoo

Adds a single item to the Cuckoo filter at key only if it does not already exist. If key does not exist, a new filter is created with default parameters.

Unlike CF.ADD, this command checks for the item before inserting. Because Cuckoo filters can return false positives, CF.ADDNX may decline to insert an item that was never actually added.

If the filter is full and expansion is disabled (EXPANSION 0), an error is returned.

Return

Integer reply:

  • 1 if the item was successfully added.
  • 0 if the item already exists in the filter (or is a false positive match).

Examples

dragonfly> CF.ADDNX cf Hello
(integer) 1

dragonfly> CF.ADDNX cf Hello
(integer) 0

dragonfly> CF.ADDNX cf World
(integer) 1

See also

CF.ADD | CF.RESERVE