Recipes.rst

Recipe

The library revolves around the idea that you can define a godd enough graph where nodes are tables with filters and vertices are meaningful relations of filtering. For instance, we can define the following schema (it comes from the dataseed/MassaliaSchema folder in the repo, which is used for integration tests in the repo) :

data Plant
  = Plant
      { id :: UUID,
        name :: Text,
        createdAt :: LocalTime,
        checkDate :: Day,
        description :: Maybe Text
      }
  deriving (Show, Generic)
deriving instance SQLRecord (Paginated PlantFilter) Plant

data PlantFilter = PlantFilter
  { id :: Maybe GQLFilterUUID,
    name :: Maybe GQLFilterText,
    checkDate :: Maybe GQLFilterDay
  }
  deriving
    ( Show,
      Generic,
      SQLFilter
    )
data Truck
  = Truck
      { id :: UUID,
        vehicleId :: Text
      }
  deriving (Show, Generic, Eq)
deriving instance SQLRecord (Paginated TruckFilter) Truck

data TruckFilter
  = TruckFilter
      { id :: Maybe GQLFilterUUID,
        vehicleId :: Maybe GQLFilterText
      }
  deriving (Show, Generic, SQLFilter)

instance SQLFilterField TruckFilter where
  filterStruct opts selection val = case selection of
    "exists_truck" -> Just $ handleExistFilter True opts selection val
    "not_exists_truck" -> Just $ handleExistFilter False opts selection val
    _ -> Nothing
    where
      handleExistFilter isExist = existsOrNotPrimitive isExist filterInside actualFilter
      filterInside = True
      actualFilter fatherTableName =
        ( mempty
            { _select = pure "1",
              _from = Just "truck",
              _where = Just condition
            },
          "exists_subquery_name"
        )
        where
          condition = ("truck" ° "plant_id") <> "=" <> (ftn ° "id")
          ftn = fromText fatherTableName