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dataset_module do | |
# User.one_to_one(:auth) | |
# User.eager_cursor(1000, :auth) do |user| | |
# user.auth # no additional query | |
# end | |
def eager_cursor rows_per_fetch=1000, *associations | |
cursor = use_cursor(rows_per_fetch: rows_per_fetch) | |
cursor.each_slice(rows_per_fetch) do |records| | |
associations.each do |assoc| | |
refl = model.association_reflection(assoc) | |
case refl[:type] | |
when :one_to_one | |
EagerCursorOneToMany | |
when :many_to_one | |
EagerCursorManyToOne | |
else | |
raise "Cannot handle: #{refl[:type]}" | |
end.new(records, refl).load | |
records.each do |r| | |
yield(r) | |
end | |
end | |
end | |
end | |
class EagerCursor < Struct.new(:records, :reflection) | |
def load | |
associations = reflection.associated_class. | |
where(association_key => records.map(&record_key)).all | |
records.each do |r| | |
if i = associations.find_index(&method(:find).curry[r]) | |
a = associations.delete_at(i) | |
r.associations[reflection[:name]] = a | |
end | |
end | |
records | |
end | |
private | |
def find record, association | |
record.public_send(record_key) == | |
association.public_send(association_key) | |
end | |
end | |
class EagerCursorOneToMany < EagerCursor | |
private | |
def association_key; reflection[:key] ; end | |
def record_key ; reflection.primary_key; end | |
end | |
class EagerCursorManyToOne < EagerCursor | |
private | |
def association_key; reflection.primary_key; end | |
def record_key ; reflection[:key] ; end | |
end | |
end |
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