Database

Defining models and tables

This project relies on Exposed to provide access to an underlying PostgreSQL database.

The Exposed DSL API is used to define the underlying tables and schema, which is then accessed or manipulated through the Exposed DAO API.

Migrations

In order to add new models, three things need to happen. Firstly, a Data Access Object and DSL table will need to be defined in com.kotlindiscord.database.DataModels and com.kotlindiscord.database.TableDefinitions. Secondly, a migration will need to be created and applied with the migrations CLI tool.

Command Line Tool

Connecting to the database

Connecting to the database requires the following environment variables to be set:

• DB_URL
  • Where the database can be found.
  • Example: localhost:5432/docker
• DB_USER
  • The user to authenticate as when connecting to the database.
  • Example: docker
• DB_PASSWORD
  • The password to use when connecting to the database.
  • Example: docker

Commands

• create
  • Requires the MIGRATIONS_DIR environment variable to be set, and point at the directory where the com.kotlindiscord.database.migrations package can be found.
    • Example: /users/{username}/IdeaProjects/database/src/main/kotlin/com/kotlindiscord/database/migrations
  • Creates a new blank migration in com.kotlindiscord.database.migrations.
  • You are required to fill in the implementations of the up() and down() methods of the created migration.
    • Migrations can include their own transaction (which will be called as a nested transaction), or they can rely on the parent transaction.
  • The tool will need to be recompiled after any new migrations have been added.
• up
  • Moves the database forwards a single migration.
• down
  • Moves the database down a single migration.
• all
  • Applies all migrations in order.