{ "PFCOUNT": { "summary": "Returns the approximated cardinality of the set(s) observed by the HyperLogLog key(s).", "complexity": "O(1) with a very small average constant time when called with a single key. O(N) with N being the number of keys, and much bigger constant times, when called with multiple keys.", "group": "hyperloglog", "since": "2.8.9", "arity": -2, "function": "pfcountCommand", "command_flags": [ "READONLY", "MAY_REPLICATE" ], "acl_categories": [ "HYPERLOGLOG" ], "key_specs": [ { "notes": "RW because it may change the internal representation of the key, and propagate to replicas", "flags": [ "RW", "ACCESS" ], "begin_search": { "index": { "pos": 1 } }, "find_keys": { "range": { "lastkey": -1, "step": 1, "limit": 0 } } } ], "arguments": [ { "name": "key", "type": "key", "key_spec_index": 0, "multiple": true } ], "reply_schema": { "description": "The approximated number of unique elements observed via PFADD", "type": "integer" } } }