# Migrate from golang-migrate
Convert a golang-migrate directory to Ptah's format, seal it, and apply it to SQLite.
Source: https://docs.ptah.run/v0.25.0/migrate-from/golang-migrate/
import { Tabs, TabItem } from '@astrojs/starlight/components';
golang-migrate directories are pairs of `NNN_name.up.sql` and `.down.sql` files.
Ptah reads that layout directly. This page converts one, including the case a
real directory always has and a clean example never does: a migration whose
down file was never written.
You will build the source directory, preview the conversion, run it, read what
Ptah wrote for the missing rollback, and apply the result to a disposable
SQLite database.
## What you need
- A `ptah` binary on your `PATH`. [Install Ptah](../../start/install/) if necessary.
- A terminal and about five minutes.
No database server, Docker, or Go toolchain is required.
## Convert the directory
### Build the golang-migrate directory
The second migration has an up file and no down file. That is the wart this
page is about, so create it exactly as shown.
```bash
mkdir -p ptah-from-golang-migrate/legacy
cd ptah-from-golang-migrate
cat > legacy/000001_create_users.up.sql <<'SQL'
CREATE TABLE users (
id INTEGER PRIMARY KEY,
email TEXT NOT NULL
);
SQL
cat > legacy/000001_create_users.down.sql <<'SQL'
DROP TABLE users;
SQL
cat > legacy/000002_add_users_email_index.up.sql <<'SQL'
CREATE UNIQUE INDEX users_email_idx ON users (email);
SQL
```
```powershell
New-Item -ItemType Directory ptah-from-golang-migrate/legacy | Out-Null
Set-Location ptah-from-golang-migrate
@'
CREATE TABLE users (
id INTEGER PRIMARY KEY,
email TEXT NOT NULL
);
'@ | Set-Content legacy/000001_create_users.up.sql
@'
DROP TABLE users;
'@ | Set-Content legacy/000001_create_users.down.sql
@'
CREATE UNIQUE INDEX users_email_idx ON users (email);
'@ | Set-Content legacy/000002_add_users_email_index.up.sql
```
### Preview the conversion
`--dry-run` writes nothing and prints the files the import would produce.
```console
ptah migrations import --from golang-migrate --source-dir ./legacy --migrations-dir ./migrations --dry-run
```
Expected output on standard output:
```text
Dry run: would write 4 migration file(s) to ./migrations
0000000001_create_users.up.sql
0000000001_create_users.down.sql
0000000002_add_users_email_index.up.sql
0000000002_add_users_email_index.down.sql
```
Four files from three. Ptah's format pairs every version, so the second
migration gets a down file whether or not the source had one.
`--from` is optional here: the source tool is detected from the directory
layout. Pass it when you want the run to fail rather than guess.
### Run the import
```console
ptah migrations import --from golang-migrate --source-dir ./legacy --migrations-dir ./migrations
```
Expected output on standard output:
```text
Wrote 4 migration file(s) to ./migrations
Wrote ./migrations/ptah.sum
0000000001_create_users.up.sql
0000000001_create_users.down.sql
0000000002_add_users_email_index.up.sql
0000000002_add_users_email_index.down.sql
```
The version numbers are widened to ten digits and the source directory is left
untouched, so this step is safe to repeat and safe to abandon.
`ptah.sum` is written by the import. Ptah checksums every migration it applies,
and the sum file is what later commands compare against.
### Read the rollback Ptah wrote for you
The second migration had no down file. Ptah wrote one rather than leaving the
pair incomplete:
```console
cat migrations/0000000002_add_users_email_index.down.sql
```
Expected output on standard output:
```text
-- No rollback was provided by the source migration.
```
That is the honest conversion of a migration that never had a rollback: a real
file with no statements in it. The last section of this page shows what that
costs, and this is the file to edit if you want a working rollback.
## Apply the result
### Validate the sealed directory
```console
ptah migrations validate --dir ./migrations
```
Expected output on standard output:
```text
OK: migrations directory matches ptah.sum
```
Editing a converted file without re-hashing fails here, before anything reaches
a database.
### Apply the converted directory
```console
ptah migrations up --db-url sqlite://app.db --migrations-dir ./migrations
```
Expected output includes, on standard output:
```text
Current version: 0
Total migrations: 2
Pending migrations: 2
```
Progress records on standard error carry timestamps and correlation IDs, so
this page does not copy those volatile fields.
### Verify the recorded state
```console
ptah migrations status --db-url sqlite://app.db --migrations-dir ./migrations
```
Expected output includes, on standard output:
```text
Current Version: 2
Total Migrations: 2
Applied Migrations: 2
Pending Migrations: 0
```
Both migrations are recorded as applied, and the directory the revision table
describes is the converted one.
## What the missing rollback costs
### Rolling back past the empty rollback is refused
```console exits=2
ptah migrations down --db-url sqlite://app.db --migrations-dir ./migrations --target 1 --confirm
```
Expected output includes, on standard error:
```text
error: error running down migrations: migration 2 has a down file with no statements (0000000002_add_users_email_index.down.sql), so a rollback would change nothing and still move the version; write the rollback, or state that it has none with `-- +ptah empty_rollback` at the top of the down file
```
Nothing changed. A rollback that ran nothing and moved the version would leave the
index in place, and the next apply of the second migration would fail on it.
### Write the rollback
Write the `DROP INDEX` the source never had:
```bash
cat > migrations/0000000002_add_users_email_index.down.sql <<'SQL'
DROP INDEX users_email_idx;
SQL
```
```powershell
@'
DROP INDEX users_email_idx;
'@ | Set-Content migrations/0000000002_add_users_email_index.down.sql
```
Seal the directory again, and roll back:
```console
ptah migrations hash --dir ./migrations
```
```console
ptah migrations down --db-url sqlite://app.db --migrations-dir ./migrations --target 1 --confirm
```
Expected output includes, on standard output:
```text
Migrations to roll back: 1
✅ Migration rollback completed successfully!
Database is now at version: 1
```
The rollback is worth writing before the directory reaches an environment you
cannot rebuild. A migration with nothing to undo
[says so instead](../../versioned/rollback/#a-down-file-with-no-statements).
## Clean up
```bash
cd ..
rm -rf ptah-from-golang-migrate
```
```powershell
Set-Location ..
Remove-Item -Recurse -Force ptah-from-golang-migrate
```
## Where this leaves you
The `legacy/` directory is no longer read by anything. Keep it in version
control until the converted directory has been applied everywhere that matters,
then delete it in a commit of its own.
If a database already has golang-migrate's `schema_migrations` table with rows
in it, do not run `ptah migrations up` against it. Record the history as
already applied first: see
[Adopt an existing database](../../start/adopt-an-existing-database/).
[Import an existing migration directory](../../versioned/import/) covers the
other source tools and the format table.