# PostgreSQL for Schemamama
A PostgreSQL adapter for the lightweight database migration system
[Schemamama](https://github.com/SkylerLipthay/schemamama). Depends on the
`postgres` crate.
## Installation
If you're using Cargo, just add Schemamama to your `Cargo.toml`:
```toml
[dependencies]
schemamama = "0.3"
schemamama_postgres = "0.2"
postgres = "0.15"
```
## Usage
First, define some migrations:
```rust
#[macro_use]
extern crate schemamama;
extern crate schemamama_postgres;
extern crate postgres;
use schemamama::{Migration, Migrator};
use schemamama_postgres::{PostgresAdapter, PostgresMigration};
struct CreateUsers;
// Instead of using sequential numbers (1, 2, 3...), you may choose to use a collaborative
// versioning scheme, such as epoch timestamps.
migration!(CreateUsers, 1, "create users table");
impl PostgresMigration for CreateUsers {
fn up(&self, transaction: &postgres::Transaction) -> Result<(), PostgresError> {
transaction.execute("CREATE TABLE users (id BIGINT PRIMARY KEY);", &[]).map(|_| ())
}
fn down(&self, transaction: &postgres::Transaction) -> Result<(), PostgresError> {
transaction.execute("DROP TABLE users;", &[]).map(|_| ())
}
}
struct CreateProducts;
migration!(CreateProducts, 2, "create products table");
impl PostgresMigration for CreateProducts {
// ...
}
```
Then, run the migrations!
```rust
let url = "postgres://postgres@localhost";
let connection = postgres::Connection::connect(url, &SslMode::None).unwrap();
let adapter = PostgresAdapter::new(&connection);
// Create the metadata tables necessary for tracking migrations. This is safe to call more than
// once (`CREATE TABLE IF NOT EXISTS schemamama` is used internally):
adapter.setup_schema();
let mut migrator = Migrator::new(adapter);
migrator.register(Box::new(CreateUsers));
migrator.register(Box::new(CreateProducts));
// Execute migrations all the way upwards:
migrator.up(None);
assert_eq!(migrator.current_version(), Some(2));
// Reverse all migrations:
migrator.down(None);
assert_eq!(migrator.current_version(), None);
```
## Testing
To run `cargo test`, you must have PostgreSQL running locally with a user role
named `postgres` with login access to a database named `postgres`. All tests
will work in the `pg_temp` schema, so the database will not be modified.
## To-do
* Make metadata table name configurable (currently locked in to `schemamama`).