HLEN

Returns the number of fields in a hash.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	HLEN
Catalog group	Hash commands
Upstream since	2.0.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

HLEN key

ffkv behavior and limits

Hash fields have independent expiration. Counted field forms use FIELDS n; HSETEX counts field/value pairs. Key TTL and field TTL are distinct.

Source: README.md:587–599; tests/bdd/features/hashes.feature.

All requests share the 8 MiB framing/1,024-argument ingress limit; normal RESP replies have 64 MiB wire/logical budgets with bounded nesting/value counts. Management and Lua origins impose smaller budgets. These are not a process RSS cap. Catalog inclusion is not exhaustive option or wire-format parity. See limits and compatibility.

Upstream metadata

The following fields come from the pinned Redis metadata, not measured ffkv performance or an assertion that ffkv enforces every upstream flag. Running COMMAND INFO/COMMAND DOCS describe the current engine.

Upstream Redis complexity: O(1)

Upstream arity: 2 (includes the command name; a negative number is a minimum).

Command flags: READONLY, FAST.

ACL categories: HASH.

Argument structure

Argument	Type	Constraints / metadata
key	key	key_spec_index: 0

Key specifications

Upstream key discovery descriptors (indexes are relative to the full command vector):

[
  {
    "flags": [
      "RO"
    ],
    "begin_search": {
      "index": {
        "pos": 1
      }
    },
    "find_keys": {
      "range": {
        "lastkey": 0,
        "step": 1,
        "limit": 0
      }
    }
  }
]

Additional pinned upstream metadata

{
  "group": "hash",
  "since": "2.0.0"
}

Metadata source · Local snapshot: src/command_metadata.json, key hlen.

BDD coverage and source examples

These are source observations, not a test run performed by this documentation build. A tag identifies scenario intent; an extracted vector identifies a command invocation, which may intentionally produce an error. Scenarios may require setup, multiple connections, persistence, cluster nodes or native-module fixtures.

• Legacy multiple writes retain last duplicate value — tests/bdd/features/hashes.feature:97; command tag and invocation observed.
• Scanning supports matching and names-only replies without changing the hash — tests/bdd/features/hashes.feature:287; invocation observed.
• Random field count modes and RESP2 values preserve duplicates correctly — tests/bdd/features/hashes.feature:702; invocation observed.
• Positive random counts return every distinct field at most once — tests/bdd/features/hashes.feature:1604; invocation observed.

Extracted command vectors

The following JSON arrays are the test harness’s argument vectors, not shell commands. Numeric arguments are converted by the harness; objects of the form {"base64":"…"} represent decoded binary bytes, not a literal JSON command argument. Preserve scenario setup and connection ordering. See the CLI guide for shell quoting and binary stdin. No reply is invented or inferred.

Legacy multiple writes retain last duplicate value — tests/bdd/features/hashes.feature:107 (I execute:)

[
  "HLEN",
  "h"
]

Next source assertion: the reply equals:

1