Module: Sequel::Plugins::DatasetAssociations::DatasetMethods

Defined in:
lib/sequel/plugins/dataset_associations.rb

Instance Method Summary collapse

Instance Method Details

#associated(name) ⇒ Object

For the association given by name, return a dataset of associated objects such that it would return the union of calling the association method on all objects returned by the current dataset.

This supports most options that are supported when eager loading. However, it will only work for limited associations or *_one associations with orders if the database supports window functions.

Raises:



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# File 'lib/sequel/plugins/dataset_associations.rb', line 70

def associated(name)
  raise Error, "unrecognized association name: #{name.inspect}" unless r = model.association_reflection(name)
  ds = r.associated_class.dataset
  sds = opts[:limit] ? self : unordered
  ds = case r[:type]
  when :many_to_one
    ds.filter(r.qualified_primary_key=>sds.select(*Array(r[:qualified_key])))
  when :one_to_one, :one_to_many
    r.send(:apply_filter_by_associations_limit_strategy, ds.filter(r.qualified_key=>sds.select(*Array(r.qualified_primary_key))))
  when :many_to_many, :one_through_one
    mds = r.associated_class.dataset.
      join(r[:join_table], r[:right_keys].zip(r.right_primary_keys)).
      select(*Array(r.qualified_right_key)).
      where(r.qualify(r.join_table_alias, r[:left_keys])=>sds.select(*r.qualify(model.table_name, r[:left_primary_key_columns])))
    ds.filter(r.qualified_right_primary_key=>r.send(:apply_filter_by_associations_limit_strategy, mds))
  when :many_through_many, :one_through_many
    fre = r.reverse_edges.first
    fe, *edges = r.edges
    edges << r.final_edge
    mds = model.
      select(*Array(r.qualify(fre[:table], fre[:left]))).
      join(fe[:table], Array(fe[:right]).zip(Array(fe[:left])), :implicit_qualifier=>model.table_name).
      where(r.qualify(fe[:table], fe[:right])=>sds.select(*r.qualify(model.table_name, r[:left_primary_key_columns])))
    edges.each{|e| mds = mds.join(e[:table], Array(e[:right]).zip(Array(e[:left])))}
    ds.filter(r.qualified_right_primary_key=>r.send(:apply_filter_by_associations_limit_strategy, mds))
  when :pg_array_to_many
    ds.filter(Sequel.expr(r.primary_key=>sds.select{Sequel.pg_array_op(r.qualify(r[:model].table_name, r[:key])).unnest}))
  when :many_to_pg_array
    ds.filter(Sequel.function(:coalesce, Sequel.pg_array_op(r[:key]).overlaps(sds.select{array_agg(r.qualify(r[:model].table_name, r.primary_key))}), false))
  else
    raise Error, "unrecognized association type for association #{name.inspect}: #{r[:type].inspect}"
  end
  r.apply_eager_dataset_changes(ds).unlimited
end