Class: Kithe::Model

Inherits:
ActiveRecord::Base
  • Object
show all
Includes:
AttrJson::NestedAttributes, AttrJson::Record, AttrJson::Record::Dirty, Indexable, StiPreload
Defined in:
app/models/kithe/model.rb

Direct Known Subclasses

Asset, Collection, Work

Instance Method Summary collapse

Methods included from Indexable

auto_callbacks?, index_with, #update_index

Constructor Details

#initialize(*_) ⇒ Model

Returns a new instance of Model.

Raises:

  • (TypeError) 


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# File 'app/models/kithe/model.rb', line 67

def initialize(*_)
  raise TypeError.new("Kithe::Model is abstract and cannot be initialized") if self.class == ::Kithe::Model
  super
end

Instance Method Details

#friendlier_id(*_) ⇒ Object

Due to rails bug, we don’t immediately have the database-provided value after create. :( If we ask for it and it’s empty, go to the db to get it github.com/rails/rails/issues/21627



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# File 'app/models/kithe/model.rb', line 80

def friendlier_id(*_)
  in_memory = super

  if !in_memory && persisted? && !@friendlier_id_retrieved
    in_memory = self.class.where(id: id).limit(1).pluck(:friendlier_id).first
    write_attribute(:friendlier_id, in_memory)
    clear_attribute_change(:friendlier_id)
    # just to avoid doing it multiple times if it's still unset in db for some reason
    @friendlier_id_retrieved = true
  end

  in_memory
end

#leaf_representative ⇒ Object

insist that leaf_representative is an Asset, otherwise return nil. nil means there is no asset leaf, and lets caller rely on leaf being an asset.



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# File 'app/models/kithe/model.rb', line 97

def leaf_representative
  leaf = super
  leaf.kind_of?(Kithe::Asset) ? leaf : nil
end

#set_leaf_representative ⇒ Object

if a representative is set, set leaf_representative by following the tree with an efficient recursive CTE to find proper value.

Normally this is called for you in callbacks, and you don’t need to call manually. But if things get out of sync, you can.

work.set_leaf_representative
work.save!



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# File 'app/models/kithe/model.rb', line 110

def set_leaf_representative
  if self.kind_of?(Kithe::Asset) # not applicable
    self.leaf_representative_id = nil
  end

  # a postgres recursive CTE to find the ultimate leaf through
  # a possible chain of works, guarding against cycles.
  # https://www.postgresql.org/docs/9.1/queries-with.html
  recursive_cte = <<~EOS
    WITH RECURSIVE find_terminal(id, link) AS (
        SELECT m.id, m.representative_id
        FROM kithe_models m
        WHERE m.id = $1
      UNION
        SELECT m.id, m.representative_id
        FROM kithe_models m, find_terminal ft
        WHERE m.id = ft.link
    ) SELECT id
      FROM find_terminal
      WHERE link IS NULL
      LIMIT 1;
  EOS

  # trying to use a prepared statement, hoping it means performance advantage
  result = self.class.connection.select_all(
    recursive_cte,
    "set_leaf_representative",
    [[nil, self.representative_id]],
    preparable: true
  ).first.try(:dig, "id")

  self.leaf_representative_id = result
end

#to_param ⇒ Object

We want friendlier_id to be in URLs, not id



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# File 'app/models/kithe/model.rb', line 73

def to_param
  friendlier_id
end