MIGRATE

Atomically transfers a key from one Redis instance to another.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	MIGRATE
Catalog group	Generic commands
Upstream since	2.6.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

MIGRATE host port <key | ""> destination-db timeout [COPY] [REPLACE]
  [AUTH password | AUTH2 username password] [KEYS key [key ...]]

ffkv behavior and limits

TTL deadlines use wall-clock time and remain absolute across restart. Key/database operations can overwrite or remove data; SCAN is incremental rather than an atomic snapshot. New typed structures remain in RAM in hybrid mode.

Source: README.md:193–195, 375–377, 584–585; tests/bdd/features/generic.feature.

Data-changing administration: use an isolated dataset or a verified backup. Lost replies have an unknown outcome; never blindly replay a destructive operation.

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: This command actually executes a DUMP+DEL in the source instance, and a RESTORE in the target instance. See the pages of these commands for time complexity. Also an O(N) data transfer between the two instances is performed.

Upstream arity: -6 (includes the command name; a negative number is a minimum).

Command flags: WRITE.

ACL categories: KEYSPACE, DANGEROUS.

Command tips: NONDETERMINISTIC_OUTPUT.

Argument structure

Argument	Type	Constraints / metadata
host	string	Required
port	integer	Required
key-selector	oneof	Required
↳ key	key	key_spec_index: 0
↳ empty-string	pure-token	token: ""
destination-db	integer	Required
timeout	integer	Required
copy	pure-token	optional; token: COPY; since: 3.0.0
replace	pure-token	optional; token: REPLACE; since: 3.0.0
authentication	oneof	optional
↳ auth	string	token: AUTH; since: 4.0.7
↳ auth2	block	token: AUTH2; since: 6.0.0
↳ ↳ username	string	Required
↳ ↳ password	string	Required
keys	key	optional; multiple; token: KEYS; key_spec_index: 1; since: 3.0.6

Key specifications

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

[
  {
    "flags": [
      "RW",
      "ACCESS",
      "DELETE"
    ],
    "begin_search": {
      "index": {
        "pos": 3
      }
    },
    "find_keys": {
      "range": {
        "lastkey": 0,
        "step": 1,
        "limit": 0
      }
    }
  },
  {
    "flags": [
      "RW",
      "ACCESS",
      "DELETE",
      "INCOMPLETE"
    ],
    "begin_search": {
      "keyword": {
        "keyword": "KEYS",
        "startfrom": -2
      }
    },
    "find_keys": {
      "range": {
        "lastkey": -1,
        "step": 1,
        "limit": 0
      }
    }
  }
]

Additional pinned upstream metadata

{
  "group": "generic",
  "since": "2.6.0",
  "history": [
    [
      "3.0.0",
      "Added the `COPY` and `REPLACE` options."
    ],
    [
      "3.0.6",
      "Added the `KEYS` option."
    ],
    [
      "4.0.7",
      "Added the `AUTH` option."
    ],
    [
      "6.0.0",
      "Added the `AUTH2` option."
    ]
  ]
}

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

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.

• Migration copies into a real target database and removes the source only for a move — tests/bdd/features/generic.feature:1408; 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.

Migration copies into a real target database and removes the source only for a move — tests/bdd/features/generic.feature:1415 (I execute:)

Fixture-dependent: {{…}} tokens are replaced by the BDD runtime (for example, node ports, generated IDs or temporary paths). This is not a standalone executable command.

[
  "MIGRATE",
  "{{target_host}}",
  "{{target_port}}",
  "transfer",
  2,
  5000,
  "COPY"
]

Next source assertion: the reply equals:

"OK"

Migration copies into a real target database and removes the source only for a move — tests/bdd/features/generic.feature:1468 (I execute:)

Fixture-dependent: {{…}} tokens are replaced by the BDD runtime (for example, node ports, generated IDs or temporary paths). This is not a standalone executable command.

[
  "MIGRATE",
  "{{target_host}}",
  "{{target_port}}",
  "transfer",
  2,
  5000,
  "REPLACE"
]

Next source assertion: the reply equals:

"OK"