Persistence

Model Requirements

Requirements for a model can be seen in https://github.com/samvera-labs/valkyrie/blob/main/lib/valkyrie/specs/shared_specs/resource.rb.

A typical model declaration looks like this:

# frozen_string_literal: true
class Book < Valkyrie::Resource
  attribute :id, Valkyrie::Types::ID.optional
  attribute :title, Valkyrie::Types::Set.optional  # default type if none is specified
  attribute :member_ids, Valkyrie::Types::Array
end

where Valkyrie::Types::Set is a Valkyrie type implemented via Dry-Types

Persistence

Metadata Adapters & Registration

There are a variety of metadata adapters available, and the most common way of using them is to instantiate them and register them with Valkyrie::MetadataAdapter via a short-name, for access later.

# in config/initializers/valkyrie.rb
Valkyrie::MetadataAdapter.register(
  Valkyrie::Persistence::Memory::MetadataAdapter.new,
  :memory
)

When registered, an adapter instance can be recalled via Valkyrie::MetadataAdapter.find

[1] pry(main)> Valkyrie::MetadataAdapter.find(:memory)
=> #<Valkyrie::Persistence::Memory::MetadataAdapter:0x007fa6ec031bd8>

Metadata Adapter instances must respond to two methods, #persister and #query_service

Persistence

Persistence in Valkyrie is done by passing an object to a persistence object, which has a defined interface (enforced by the shared spec.)

Saving an Object

metadata_adapter = Valkyrie::MetadataAdapter.find(:memory)
book = Book.new # => #<Book:0x007fe383479988 @id=nil, @title=[], @member_ids=[]>
book = metadata_adapter.persister.save(resource: book)
book.id # => #<Valkyrie::ID:0x007fe38353ac78 @id="692ccfd5-414a-42f9-a8d5-c1605e7baef9">

Saving to two backends

adapter1 = Valkyrie::MetadataAdapter.find(:postgres)
adapter2 = Valkyrie::MetadataAdapter.find(:fedora)
composite_persister = Valkyrie::Persistence::CompositePersister.new(adapter1.persister, adapter2.persister)
book = Book.new
composite_persister.save(resource: book)

For more on saving to two backends, see https://github.com/samvera-labs/valkyrie/wiki/Combining-Persistence-&-Indexing

Deleting an Object

metadata_adapter.persister.delete(resource: book)

Deleting all Objects

metadata_adapter.persister.wipe!

Continue on to Queries