SISMEMBER

Determines whether a member belongs to a set.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	SISMEMBER
Catalog group	Set commands
Upstream since	1.0.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

SISMEMBER key member

ffkv behavior and limits

Members are binary-safe and unique. Sampling and pop order are not stable; preserve the distinction between destructive pops and reads. Hybrid mode does not offload set bodies.

Source: README.md:275–295, 810–825; tests/bdd/features/sets.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: 3 (includes the command name; a negative number is a minimum).

Command flags: READONLY, FAST.

ACL categories: SET.

Argument structure

Argument	Type	Constraints / metadata
key	key	key_spec_index: 0
member	string	Required

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": "set",
  "since": "1.0.0"
}

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

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.

• Membership queries preserve duplicate query positions — tests/bdd/features/sets.feature:57; command tag and invocation observed.
• SDIFFSTORE can overwrite an input after computing the result — tests/bdd/features/sets.feature:197; invocation observed.
• SINTERSTORE can overwrite an input after computing the result — tests/bdd/features/sets.feature:237; invocation observed.
• SUNIONSTORE can overwrite an input after computing the result — tests/bdd/features/sets.feature:277; invocation observed.
• Moves preserve the source on wrongtype and handle same-key aliases — tests/bdd/features/sets.feature:507; invocation observed.
• SISMEMBER validates every source without replacing the destination — tests/bdd/features/sets.feature:908; command tag and 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.

Membership queries preserve duplicate query positions — tests/bdd/features/sets.feature:63 (I execute:)

[
  "SISMEMBER",
  "s",
  "a"
]

Next source assertion: the reply equals:

1

SDIFFSTORE can overwrite an input after computing the result — tests/bdd/features/sets.feature:211 (I execute:)

[
  "SISMEMBER",
  "a",
  "a"
]

Next source assertion: the reply equals:

1

SINTERSTORE can overwrite an input after computing the result — tests/bdd/features/sets.feature:251 (I execute:)

[
  "SISMEMBER",
  "a",
  "b"
]

Next source assertion: the reply equals:

1