SQL » Schemas

The SQL adapter adds its own schema types and association declarations to the built-in Relation Schema feature.

Inferring Attributes

If you don't want to declare all attributes explicitly, you can tell rom-sql to infer attributes from an existing schema.

Inference will define normal attributes, foreign keys and primary key (even when it's a composite primary key).

To infer a schema automatically:

require 'rom-sql'

class Users < ROM::Relation[:sql]
  schema(infer: true) # that's it
end

Coercions

Relations and commands can coerce output and input data automatically based on your schema attributes. Default attribute types in schemas are used for input coercions in commands, if you want to apply additional coercions when relations read their data, you can do it via :read type in schema definitions:

class Posts < ROM::Relation[:sql]
  schema(infer: true) do
    attribute :status, Types::String, read: Types.Constructor(Symbol, &:to_sym)
  end
end

id = posts.insert(title: 'Hello World', status: :draft)

posts.by_pk(1).one
# => {:id => 1, :title => "Hello World", status: :draft }

PostgreSQL Types

When you define relation schema attributes using custom PG types, the values will be automatically coerced before executing commands, so you don't have to handle that yourself.

require 'rom-sql'

class Users < ROM::Relation[:sql]
  schema do
    attribute :meta, Types::PG::JSONB
    attribute :tags, Types::PG::Array('varchar')
    attribute :info, Types::PG::HStore
  end
end

Users.schema[:meta][{ name: 'Jane' }].class
# Sequel::Postgres::JSONBHash

Users.schema[:meta][[1, 2, 3]].class
# Sequel::Postgres::JSONBArray

Users.schema[:tags][%w(red green blue)].class
# => Sequel::Postgres::PGArray

Users.schema[:info][{ some: 'info' }].class
# => Sequel::Postgres::HStore

For getting hstore to work be sure you have the pg_hstore extension loaded.