79 lines
2.8 KiB
Markdown
79 lines
2.8 KiB
Markdown
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# @markup markdown
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# @title Database
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# Chronicle Database
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Chronicle leverages a database for persistent storage. It uses ActiveRecord for
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interfacing with the supported database types, performing migrations, and
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interacting with models.
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## Supported Databases
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### Currently Supported:
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- SQLite
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### Planned Support:
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- PostgreSQL
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- MySQL
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- MariaDB
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## Creating the Database
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There's a Rake task for creating the database according to ActiveRecord: `rake
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db:create`. For configuration, check out `config/db.yml`. The default
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configuration will create a SQLite3 database at `db/chronicle-bot.db`.
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## Working With the Migrations
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ActiveRecord migrations are database-agnostic schema alterations, stored as
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code. This allows Chronicle to support multiple different database
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architectures, without having to write custom code for each one. Migrations can
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represent changes tied to new versions, or additional database configuration
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tied to an add-on or protocol, for example.
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To apply the migrations, use the Rake task `rake db:migrate`.
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To roll-back the migrations, use the Rake task `rake db:down`.
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### Provided Migrations
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By default, Chronicle includes a migration for setting up the "general" table,
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which provides details around the bot itself.
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It also includes a migration for the Custom Commands add-on, which creates a
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table for storing the commands and responses, along with the room ID the command
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was created in.
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Each of these migrations include a "roll-back" solution, which simply drops the
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corresponding tables.
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### Writing Additional Migrations
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The most important thing when creating new migrations is to follow the naming
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convention:
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```
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XXXX_name_of_migration.rb
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```
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The Rake tasks for working with migrations will look at every file in the
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`db/migrate/` directory, and sort them. It will `require` those files, and then
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compile a list of the classes within those files according to specific logic: it
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takes the file name, drops the numbers at the beginning, and converts the file
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name from snake case and to camel case, dropping the file extension. For example,
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"0000_create_general.rb" will be processed to the class named "CreateGeneral",
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which will be added to a list. The Rake task will then go through each the list
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of all classes and run the "migrate" method of each class, passing it "up" if
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migrations are being applied, or "down" if migrations are being rolled-back.
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Generally speaking, the number for the migration is mostly important for sorting
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order. However, a simple naming convention can help distinguish between types of
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migrations, by changing the 2nd-position digit:
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- For migrations tied to Chronicle functionality, use `00XX`.
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- For migrations tied to addon functionality, use `01XX`.
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- For migrations tied to protocol functionality, use `02XX`.
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- For any miscellaneous migrations, use `03XX`.
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