# pg

Helpers for working with postgres

## Usage

### `with-test-db.sh`

This script allows you to run any command with a fresh, ephemeral/single-use postgres database available. When the script starts a Dockerized postgres container starts-up, and when the script completes that container is removed.

The environment variable `DATABASE_URL` will be set with a connection string that can be used to connect to the database. The [`PG*` environment variables](https://www.postgresql.org/docs/current/libpq-envars.html) that are recognized by libpq (i.e. used by the `psql` client) are also set.

**Example**

```
$ ./with-test-db.sh psql -c 'select 1;'
[+] Running 1/1
 ⠿ Container pg-db_test-1  Healthy                                                           1.8s

 ?column?
----------
        1
(1 row)


[+] Running 1/1
 ⠿ Container pg-db_test-1  Stopped                                                           0.1s
Going to remove pg-db_test-1
[+] Running 1/0
 ⠿ Container pg-db_test-1  Removed
```

### `docker-compose.yaml`

The Docker compose file can be used to run containerized versions of postgres either for single use (as is used by `with-test-db.sh`), or for longer-term use. These are setup as separate services named `test_db` and `db` respectively. In both cases the database is available on the host machine's `localhost` and credentials are:

- Username: pg
- Password: password

However, each service uses a different port, documented below, to avoid conflicts.

#### `test_db` service for single use

The single-use `test_db` service does not have any persistent storage. When the container is removed, data in the database disappears with it.

This service runs on port `5433`.

```
$ docker compose up test_db   # start container
$ docker compose stop test_db # stop container
$ docker compose rm test_db   # remove container
```

#### `db` service for persistent use

The `db` service has persistent storage on the host machine managed by Docker under a volume named `pg_plc_db`. When the container is removed, data in the database will remain on the host machine. In order to start fresh, you would need to remove the volume.

This service runs on port `5432`.

```
$ docker compose up db -d    # start container
$ docker compose stop db     # stop container
$ docker compose rm db       # remove container
$ docker volume rm pg_plc_db # remove volume
```