ZDIFFSTORE

Stores the difference of multiple sorted sets in a key.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	ZDIFFSTORE
Catalog group	Sorted set commands
Upstream since	6.2.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

ZDIFFSTORE destination numkeys key [key ...]

ffkv behavior and limits

Scores and lexicographic ranges are separate query modes. Do not rely on random-pop order; sorted-set storage remains RAM-resident in hybrid mode.

Source: README.md:275–295, 810–825; tests/bdd/features/sorted_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(L + (N-K)log(N)) worst case where L is the total number of elements in all the sets, N is the size of the first set, and K is the size of the result set.

Upstream arity: -4 (includes the command name; a negative number is a minimum).

Command flags: WRITE, DENYOOM.

ACL categories: SORTEDSET.

Argument structure

Argument	Type	Constraints / metadata
destination	key	key_spec_index: 0
numkeys	integer	Required
key	key	multiple; key_spec_index: 1

Key specifications

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

[
  {
    "flags": [
      "OW",
      "UPDATE"
    ],
    "begin_search": {
      "index": {
        "pos": 1
      }
    },
    "find_keys": {
      "range": {
        "lastkey": 0,
        "step": 1,
        "limit": 0
      }
    }
  },
  {
    "flags": [
      "RO",
      "ACCESS"
    ],
    "begin_search": {
      "index": {
        "pos": 2
      }
    },
    "find_keys": {
      "keynum": {
        "keynumidx": 0,
        "firstkey": 1,
        "step": 1
      }
    }
  }
]

Additional pinned upstream metadata

{
  "group": "sorted_set",
  "since": "6.2.0"
}

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

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.

• Difference store can overwrite its source and clears destination TTL — tests/bdd/features/sorted_sets.feature:609; command tag and invocation observed.
• Invalid store options and source types do not destroy destination — tests/bdd/features/sorted_sets.feature:975; command tag and invocation observed.
• Only union and intersection accept regular set inputs — tests/bdd/features/sorted_sets.feature:1276; 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.

Difference store can overwrite its source and clears destination TTL — tests/bdd/features/sorted_sets.feature:615 (I execute:)

[
  "ZDIFFSTORE",
  "left",
  "2",
  "left",
  "right"
]

Next source assertion: the reply equals:

2

Only union and intersection accept regular set inputs — tests/bdd/features/sorted_sets.feature:1303 (I execute:)

[
  "ZDIFFSTORE",
  "destination",
  "1",
  "plain"
]

Next source assertion: the reply is an error with code “WRONGTYPE”

Invalid store options and source types do not destroy destination — tests/bdd/features/sorted_sets.feature:1007 (I execute:)

[
  "ZDIFFSTORE",
  "keep",
  "1",
  "left",
  "WITHSCORES"
]

Next source assertion: the reply is an error with code “ERR”