waterline-schema

Waterline Schema

This is the core schema builder used in the Waterline ORM. It is responsible for taking an attributes object from a Collection and turning it into a fully fledged schema object.

It's mainly tasked with figuring out and expanding associations between Collections.

Schema Format

A Waterline schema is a javascript object that maps to a generalized database schema format. An adapter should be able to take it and build out a schema definition including join tables in a relational database.

Belongs To

Belongs to relationships are defined by adding a property to a collection's attributes with a model property that points to another collection.

attributes: {
  user: { model: 'user' }
}

Should create the following after being run through the schema.

attributes: {
  user: {
    columnName: 'user_id',
    type: 'integer',
    foreignKey: true,
    references: 'user',
    on: 'id'
  }
}

Has Many

Has many relationships are defined by adding a property to a collection's attributes with a collection property that points to another collection. This isn't used for the actual database structure in a relational system but could be helpful in a nosql database. It is also used internally inside of Waterline. A via key is required to point to a foriegn key.

attributes: {
  users: {
    collection: 'user',
    via: 'foo'
  }
}

Should create the following after being run through the schema.

attributes: {
  users: {
    collection: 'user',
    references: 'user',
    on: 'user_id',
    via: 'foo'
  }
}

Many To Many

Many To Many relationships are defined by adding a collection property on two Collections that point to each other. This will create an additional collection in the schema that maps out the relationship between the two. It will rewrite the foreign keys on the two collections to reference the new join collections. A via key is required on both so that the relationships can be properly mapped.

// Foo Collection
attributes: {
  bars: {
    collection: 'bar',
    via: 'foos'
  }
}

// Bar Collection
attributes: {
  foos: {
    collection: 'foo',
    via: 'bars'
  }
}

Should create the following after being run through the schema.

// Foo Collection
attributes: {
  id: {
    type: 'integer',
    autoIncrement: true,
    primaryKey: true,
    unique: true
  },
  bars: {
    collection: 'bar_foos__foo_bars',
    references: 'bar_foos__foo_bars',
    on: 'foo__bars',
    via: 'bar_foos'
  }
}

// Bar Collection
attributes: {
  id: {
    type: 'integer',
    autoIncrement: true,
    primaryKey: true,
    unique: true
  },
  foos: {
    collection: 'bar_foos__foo_bars',
    references: 'bar_foos__foo_bars',
    on: 'bar_foos',
    via: 'foo_bars'
  }
}

// bar_foos__foo_bars Collection
attributes: {
  bar_foos: {
    columnName: 'bar_foos',
    type: 'integer',
    foreignKey: true,
    references: 'bar',
    on: 'id',
    groupKey: 'bar'
  },
  foo_bars: {
    columnName: 'foo_bars',
    type: 'integer',
    foreignKey: true,
    references: 'foo',
    on: 'id',
    groupKey: 'foo'
  }
}