app/graphql/lazy_loading/line_stop_areas.rb
module LazyLoading
class LineStopAreas
def initialize(query_ctx, line_id)
@line_id = line_id
# Initialize the loading state for this query or get the previously-initiated state
@lazy_state = query_ctx[:lazy_find_line_stop_areas] ||= {
pending_ids: Set.new,
loaded_ids: {},
}
# Register this ID to be loaded later:
@lazy_state[:pending_ids] << line_id
end
# Return the loaded record, hitting the database if needed
def stop_areas
# Check if the record was already loaded:
loaded_records = @lazy_state[:loaded_ids][@line_id]
if loaded_records
# The pending IDs were already loaded so return the result of that previous load
loaded_records
else
# The record hasn't been loaded yet, so hit the database with all pending IDs
pending_ids = @lazy_state[:pending_ids].to_a
stop_areas = Chouette::StopArea.joins(:stop_points => [:route => :line])
.where(:lines => {:id => pending_ids})
.select('stop_areas.*', 'lines.id as line_id')
# Fill and clean the map
stop_areas.each do |stop|
@lazy_state[:loaded_ids][stop.line_id] ||= []
@lazy_state[:loaded_ids][stop.line_id] << stop
end
@lazy_state[:pending_ids].clear
@lazy_state[:loaded_ids].transform_values! { |v| v.uniq } # The request returns the same stop multiple times
# Now, get the matching stop_areas from the loaded result:
@lazy_state[:loaded_ids][@line_id]
end
end
end
end