mmk import

Copies the history from a migrate-mongo changelog collection into mmk, so mmk knows which migrations already ran. You do this once, when you switch. The source collection is only read, never changed.

npx mmk import [options]

For the full walkthrough, see Moving from migrate-mongo.

Examples

npx mmk import --dry-run          # show what would be copied, write nothing
npx mmk import                    # copy it
npx mmk import --from old_log     # the source collection has another name

$ npx mmk import
Loaded config from mmk.config.js
✔ Imported 3 record(s) from "changelog" → "_mmk_migrations"
┌─────────────────────────────────┬───────┬─────────────────────┬────────────┐
│ Migration                       │ Batch │ Applied At          │ Checksum   │
├─────────────────────────────────┼───────┼─────────────────────┼────────────┤
│ 20250301100000-create-users.js  │ 1     │ 2025-03-01 15:35:00 │ recomputed │
├─────────────────────────────────┼───────┼─────────────────────┼────────────┤
│ 20250412083000-add-sku-index.js │ 2     │ 2025-04-12 14:10:00 │ recomputed │
├─────────────────────────────────┼───────┼─────────────────────┼────────────┤
│ 20250720140000-split-address.js │ 3     │ 2025-07-20 19:40:00 │ recomputed │
└─────────────────────────────────┴───────┴─────────────────────┴────────────┘

Options

Option	Default	What it does
--from <collection>	changelog	The migrate-mongo collection to read.
--to <collection>	your migrationsCollection	Where to write the records.
--dry-run	off	Show what would be imported, write nothing.
--trust-hash	off	Use migrate-mongo's stored fileHash without checking it against the file.
--force	off	Import even though the target already has records.
--no-lock	off	Don't take the lock. Only for local development.
--json	off	Print the result as JSON.

--from and --to can't be the same collection.

Checksums

The Checksum column says where each checksum came from:

1. If migrate-mongo stored a fileHash and it matches the file on disk (or you passed --trust-hash), that hash is reused.
2. Otherwise it's computed from the file now (recomputed).
3. If the file is gone, the checksum is left empty and you get a warning.

If the target isn't empty

If mmk's history collection already has records, import stops with IMPORT_TARGET_NOT_EMPTY. --force imports anyway, and the imported batches are numbered after the existing ones. Running a forced import twice gives the same result both times.

Imported records are forward-only

Imported records are marked origin: 'migrate-mongo'. Their files use migrate-mongo's up(db, client) style, which mmk can't run safely, so mmk down and mmk redo refuse them before touching anything. Migrations you write afterwards with mmk create roll back as normal.

With a namespace

If several repos shared one migrate-mongo changelog, set a namespace in each repo and run mmk import in each:

• A repo only imports records whose file is in its own migrations folder. The others are listed as skipped (notInRepo in --json).
• Imported records get this repo's namespace.
• The "target isn't empty" check and the batch numbers only count this namespace, so other repos never get in the way.