> For the complete documentation index, see [llms.txt](https://shipclojure.gitbook.io/shipclojure-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shipclojure.gitbook.io/shipclojure-docs/backend/migrations.md).

# Migrations

Shipclojure uses [migratus](https://github.com/yogthos/migratus) to handle migrations. For ease of creating migrations, there is the [migrations namespace](https://github.com/shipclojure/shipclojure/blob/main/env/dev/clj/migrations.clj)

## Store

By default, ShipClojure stores migrations in a table in the main DB

> See `db.sql/migrations` key in [system.edn](https://github.com/shipclojure/shipclojure/blob/main/resources/system.edn)

## Creating a migration

Let's say you need to create a new image table in the DB to store user images.

1. Visit [migrations.clj](https://github.com/shipclojure/shipclojure/blob/main/env/dev/clj/migrations.clj)
2. In the last comment, you'll see imported the `migration-config` from `user`
3. Write in the same comment

```clojure
  (create-migration (migration-config) "add-images-table" :sql)
```

4. Evaluate this in the REPL
5. Expect to see 2 new files `{current-date}-add-images-table.{up,down}.sql` in `resources/db/migrations`
6. Add the correct up & down configurations, and reset the integrant system. The migrations will be applied automatically

> *Important:* If you want to include multiple statements in the same migration file there is a special notation (`--;;`) you need to use, otherwise you'll get an error `Too many update results were returned`:

```sql
ALTER TABLE user_account
    DROP COLUMN IF EXISTS image_url;
--;;
CREATE TABLE user_image (
    id TEXT NOT NULL PRIMARY KEY,
    alt_text TEXT,
    content_type TEXT NOT NULL,
    blob BYTEA NOT NULL,
    created_at TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
    user_id TEXT NOT NULL REFERENCES user_account(id) ON DELETE CASCADE ON UPDATE CASCADE
);
--;;
CREATE UNIQUE INDEX user_image_user_id_idx ON user_image(user_id);
```

## Rolling back migrations

To roll back migrations, use `user/rollback-latest-migration`


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://shipclojure.gitbook.io/shipclojure-docs/backend/migrations.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.