SETRANGE

Overwrites a part of a string value with another by an offset. Creates the key if it doesn’t exist.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	SETRANGE
Catalog group	String commands
Upstream since	2.2.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

SETRANGE key offset value

ffkv behavior and limits

Keys and values are binary-safe bytes. Conditional SET and DELEX comparisons use the stored bytes; DIGEST uses XXH3, not a cryptographic digest.

Source: README.md:571–585; src/engine/strings.rs; tests/bdd/features/strings.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), not counting the time taken to copy the new string in place. Usually, this string is very small so the amortized complexity is O(1). Otherwise, complexity is O(M) with M being the length of the value argument.

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

Command flags: WRITE, DENYOOM.

ACL categories: STRING.

Argument structure

Argument	Type	Constraints / metadata
key	key	key_spec_index: 0
offset	integer	Required
value	string	Required

Key specifications

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

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

Additional pinned upstream metadata

{
  "group": "string",
  "since": "2.2.0"
}

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

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.

• Sparse writes zero fill holes and retain TTL — tests/bdd/features/strings.feature:891; command tag and invocation observed.
• String type errors never destroy a collection (Scenario Outline) — tests/bdd/features/strings.feature:1139; 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.

Sparse writes zero fill holes and retain TTL — tests/bdd/features/strings.feature:897 (I execute:)

[
  "SETRANGE",
  "text",
  "1",
  "Z"
]

Next source assertion: the reply equals:

3

String type errors never destroy a collection — tests/bdd/features/strings.feature:1145 (I execute:)

Expanded from an actual Examples row: argv=["SETRANGE","typed","0","replacement"], code=WRONGTYPE.

[
  "SETRANGE",
  "typed",
  "0",
  "replacement"
]

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

Sparse writes zero fill holes and retain TTL — tests/bdd/features/strings.feature:913 (I execute:)

[
  "SETRANGE",
  "text",
  "5",
  "x"
]

Next source assertion: the reply equals:

6