[DRAFT PR] ORMTables -- DatabaseTables with less boilerplate

[guineawheek]

Overview

ORM tables are a new variant on DatabaseTables:

• they are defined from class attributes
• initial_create, initial_migrate, get_by, delete, and update_or_add (upsert) are handled for you
• ability to instantiate objects directly from the results of SQL queries using from_record
• inferred versioning from column parameters (mostly adds columns)

Differences from DatabaseTable:

• __uniques__ MUST be a tuple of primary key column names! Do not set it to a string! Runtime will check for this and yell at you!
  • By default, __version__ is None. This means that versions/migrations will be computed from arguments given to Column (see next section)
  • initial_create/initial_migrate will create the latest version of the table, rather than version 0.

Versioning:

• In general, columns should be defined using the latest version of the schema.
  • If your table previously had an id field that's now channel_id, name the thing channel_id: int = db.Column("bigint NOT NULL")
  • The default versioning scheme looks at db.Column.version to see when the first version a column is introduced. It will then either just add the column using ALTER TABLE ADD COLUMN or run a custom script via whatever script is in Column.alter_tbl.
  • You can set version to a List for the default functionality of calling migration functions in order. You can also override cls.initial_create and cls.initial_migrate to have tables created at version 0 and upgraded all the way up, like DatabaseTable.

Worked example:

    class StarboardConfig(db.ORMTable):
        __tablename__ = 'starboard_settings'
        __uniques__ = ('guild_id',) 

        # the column definitions
        guild_id: int     = db.Column("bigint NOT NULL")
        channel_id: int   = db.Column("bigint NOT NULL")
        star_emoji: str   = db.Column("varchar NOT NULL")
        cancel_emoji: str = db.Column("varchar")
        threshold: int    = db.Column("bigint NOT NULL")
        # this parameter could be added later down the line, and it will be added using ALTER TABLE.
        some_new_col: int = db.Column("bigint NOT NULL DEFAULT 10", version=1)

TODO

• [ ] add and test a sample class for test instrumentation
• [ ] feedback from other dozer maintainers
• [ ] adapt agreed-upon classes to paradigm