LINSERT

Inserts an element before or after another element in a list.

Browse all commands · Upstream source documentation

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

Syntax

LINSERT key <BEFORE | AFTER> pivot element

ffkv behavior and limits

A successful pop removes the item immediately: Redis list queues have no acknowledgement or automatic redelivery. Blocking calls do not wait in EXEC or Lua. Only large list/native-job bodies are SSD-offloaded in hybrid mode.

Source: README.md:155–174, 810–825; tests/bdd/features/lists.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(N) where N is the number of elements to traverse before seeing the value pivot. This means that inserting somewhere on the left end on the list (head) can be considered O(1) and inserting somewhere on the right end (tail) is O(N).

Upstream arity: 5 (includes the command name; a negative number is a minimum).

Command flags: WRITE, DENYOOM.

ACL categories: LIST.

Argument structure

Argument	Type	Constraints / metadata
key	key	key_spec_index: 0
where	oneof	Required
↳ before	pure-token	token: BEFORE
↳ after	pure-token	token: AFTER
pivot	string	Required
element	string	Required

Key specifications

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

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

Additional pinned upstream metadata

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

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

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.

• Insertion resolves the first pivot and reports missing pivots without mutation — tests/bdd/features/lists.feature:273; command tag and invocation observed.
• Resolved insertion and batch movement recover with ordering and binary values intact — tests/bdd/features/lists.feature:882; command tag and invocation observed.
• An insertion wakes an exact batch after an earlier insufficient push — tests/bdd/features/lists.feature:938; command tag and invocation observed.
• List commands reject incompatible source values without replacing them (Scenario Outline) — tests/bdd/features/lists.feature:1047; 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.

An insertion wakes an exact batch after an earlier insufficient push — tests/bdd/features/lists.feature:966 (I execute:)

[
  "LINSERT",
  "source",
  "BEFORE",
  "c",
  "b"
]

Next source assertion: the reply equals:

3

Insertion resolves the first pivot and reports missing pivots without mutation — tests/bdd/features/lists.feature:287 (I execute:)

[
  "LINSERT",
  "q",
  "AFTER",
  "pivot",
  "after"
]

Next source assertion: the reply equals:

6

Resolved insertion and batch movement recover with ordering and binary values intact — tests/bdd/features/lists.feature:884 (the following commands succeed:)

[
  "LINSERT",
  "source",
  "AFTER",
  "a",
  "middle"
]