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300 lines
13 KiB
Haskell
300 lines
13 KiB
Haskell
{-# OPTIONS_HADDOCK not-home #-}
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-- | Supporting functionality for fine-grained dependency tracking.
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module Hasura.Incremental.Internal.Dependency where
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import Hasura.Prelude
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import qualified Data.Dependent.Map as DM
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import qualified Data.HashMap.Strict as Map
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import qualified Data.HashMap.Strict.InsOrd as OMap
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import qualified Data.URL.Template as UT
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import qualified Language.GraphQL.Draft.Syntax as G
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import qualified Network.URI.Extended as N
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import Data.Aeson (Value)
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import Data.ByteString (ByteString)
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import Data.CaseInsensitive (CI)
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import Data.Functor.Classes (Eq1 (..), Eq2 (..))
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import Data.Functor.Const
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import Data.GADT.Compare
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import Data.Int
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import Data.Scientific (Scientific)
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import Data.Set (Set)
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import Data.Text.NonEmpty
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import Data.Time
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import Data.Vector (Vector)
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import Data.Word
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import GHC.Generics (Generic (..), K1 (..), M1 (..), U1 (..), V1,
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(:*:) (..), (:+:) (..))
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import System.Cron.Types
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import Hasura.Incremental.Select
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-- | A 'Dependency' represents a value that a 'Rule' can /conditionally/ depend on. A 'Dependency'
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-- is created using 'newDependency', and it can be “opened” again using 'dependOn'. What makes a
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-- 'Dependency' useful is the way it cooperates with 'cache'---if a 'Dependency' is passed to a
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-- cached rule, but that rule (or any of its sub-rules) never “opens” it using 'dependOn', then
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-- subsequent executions of the rule will ignore the 'Dependency' when computing whether or not it
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-- is necessary to re-execute the rule.
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--
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-- The above functionality is useful on its own to express conditional dependencies, but even more
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-- useful is the ability to express /partial/ dependencies. For example, if a 'Dependency' contains
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-- a 'HashMap', a rule can choose to only depend on the value associated with a particular key by
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-- using 'selectKeyD' (or the more general 'selectD'). Only the parts that are actually used will be
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-- counted when computing whether a rule needs to be re-executed.
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data Dependency a = Dependency !(DependencyKey a) !a
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instance (Eq a) => Eq (Dependency a) where
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Dependency _ a == Dependency _ b = a == b
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-- | Applies a 'Selector' to select part of a 'Dependency'.
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selectD :: (Select a) => Selector a b -> Dependency a -> Dependency b
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selectD k (Dependency dk a) = Dependency (DependencyChild k dk) (select k a)
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-- | Selects a single key from a dependency containing a map-like data structure.
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selectKeyD :: (Select a, Selector a ~ ConstS k v) => k -> Dependency a -> Dependency v
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selectKeyD = selectD . ConstS
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-- | Tracks whether a 'Dependency' is a “root” dependency created by 'newDependency' or a “child”
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-- dependency created from an existing dependency using 'selectD'.
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data DependencyKey a where
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DependencyRoot :: !(UniqueS a) -> DependencyKey a
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DependencyChild :: (Select a) => !(Selector a b) -> !(DependencyKey a) -> DependencyKey b
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instance GEq DependencyKey where
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DependencyRoot a `geq` DependencyRoot b
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| Just Refl <- a `geq` b
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= Just Refl
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DependencyChild a1 a2 `geq` DependencyChild b1 b2
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| Just Refl <- a2 `geq` b2
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, Just Refl <- a1 `geq` b1
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= Just Refl
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_ `geq` _ = Nothing
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instance GCompare DependencyKey where
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DependencyRoot a `gcompare` DependencyRoot b = case gcompare a b of
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GLT -> GLT
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GEQ -> GEQ
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GGT -> GGT
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DependencyChild a1 a2 `gcompare` DependencyChild b1 b2 = case gcompare a2 b2 of
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GLT -> GLT
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GEQ -> case gcompare a1 b1 of
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GLT -> GLT
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GEQ -> GEQ
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GGT -> GGT
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GGT -> GGT
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DependencyRoot _ `gcompare` DependencyChild _ _ = GLT
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DependencyChild _ _ `gcompare` DependencyRoot _ = GGT
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-- | A typeclass that implements the dependency-checking machinery used by 'cache'. Morally, this
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-- class is like 'Eq', but it only checks the parts of a 'Dependency' that were actually accessed on
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-- the previous execution. It is highly unlikely you will need to implement any 'Cacheable'
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-- instances yourself; the default implementation uses 'Generic' to derive an instance
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-- automatically.
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class (Eq a) => Cacheable a where
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unchanged :: Accesses -> a -> a -> Bool
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default unchanged :: (Generic a, GCacheable (Rep a)) => Accesses -> a -> a -> Bool
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unchanged accesses a b = gunchanged (from a) (from b) accesses
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{-# INLINABLE unchanged #-}
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-- | A mapping from root 'Dependency' keys to the accesses made against those dependencies.
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newtype Accesses = Accesses { unAccesses :: DM.DMap UniqueS Access }
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instance Semigroup Accesses where
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Accesses a <> Accesses b = Accesses $ DM.unionWithKey (const (<>)) a b
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instance Monoid Accesses where
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mempty = Accesses DM.empty
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recordAccess :: DependencyKey a -> Access a -> Accesses -> Accesses
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recordAccess depKey !access (Accesses accesses) = case depKey of
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DependencyRoot rootKey -> Accesses $ DM.insertWith' (<>) rootKey access accesses
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DependencyChild selector parentKey ->
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recordAccess parentKey (AccessedParts $ DM.singleton selector access) (Accesses accesses)
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-- | Records the accesses made within a single 'Dependency' and its children. The 'Semigroup'
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-- instance for 'Access' computes a least upper bound:
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--
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-- * 'AccessedAll' serves as the top of the lattice and records the dependency’s entire value was
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-- accessed.
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-- * 'AccessedParts' records a set of accesses for individual parts of a dependency.
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data Access a where
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AccessedAll :: (Cacheable a) => Access a
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AccessedParts :: (Select a) => !(DM.DMap (Selector a) Access) -> Access a
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instance Semigroup (Access a) where
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AccessedAll <> _ = AccessedAll
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_ <> AccessedAll = AccessedAll
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AccessedParts a <> AccessedParts b = AccessedParts $ DM.unionWithKey (const (<>)) a b
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instance (Cacheable a) => Cacheable (Dependency a) where
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unchanged accesses (Dependency key1 v1) (Dependency _ v2) =
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-- look up which parts of this dependency were previously accessed
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case lookupAccess key1 of
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-- looking up the access was enough to determine the result
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Left result -> result
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-- otherwise, look through the accessed children
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Right access -> unchangedBy v1 v2 access
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where
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-- Looks up the Access associated with the given DependencyKey, if it exists.
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lookupAccess :: DependencyKey b -> Either Bool (Access b)
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lookupAccess = \case
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DependencyRoot key -> handleNoAccess $ DM.lookup key (unAccesses accesses)
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DependencyChild selector key -> lookupAccess key >>= \case
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AccessedAll -> Left (unchanged accesses v1 v2)
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AccessedParts parts -> handleNoAccess $ DM.lookup selector parts
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where
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-- if this dependency was never accessed, then it’s certainly unchanged
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handleNoAccess = maybe (Left True) Right
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-- Walks the given values guided by the given Access, checking that all the subparts
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-- identified by the AccessedAll leaves are unchanged.
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unchangedBy :: forall b. b -> b -> Access b -> Bool
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unchangedBy a b = \case
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AccessedAll -> unchanged accesses a b
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AccessedParts parts -> DM.foldrWithKey reduce True parts
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where
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reduce :: (Select b) => Selector b c -> Access c -> Bool -> Bool
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reduce selector = (&&) . unchangedBy (select selector a) (select selector b)
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-- -------------------------------------------------------------------------------------------------
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-- boilerplate Cacheable instances
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instance Cacheable Char where unchanged _ = (==)
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instance Cacheable Double where unchanged _ = (==)
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instance Cacheable Int where unchanged _ = (==)
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instance Cacheable Int32 where unchanged _ = (==)
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instance Cacheable Integer where unchanged _ = (==)
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instance Cacheable Scientific where unchanged _ = (==)
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instance Cacheable Text where unchanged _ = (==)
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instance Cacheable NonEmptyText where unchanged _ = (==)
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instance Cacheable N.URIAuth where unchanged _ = (==)
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instance Cacheable G.Name where unchanged _ = (==)
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instance Cacheable DiffTime where unchanged _ = (==)
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instance Cacheable NominalDiffTime where unchanged _ = (==)
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instance Cacheable UTCTime where unchanged _ = (==)
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instance Cacheable Day where unchanged _ = (==)
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instance Cacheable TimeOfDay where unchanged _ = (==)
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instance Cacheable LocalTime where unchanged _ = (==)
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instance Cacheable ByteString where unchanged _ = (==)
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instance Cacheable Float where unchanged _ = (==)
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instance Cacheable Word8 where unchanged _ = (==)
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-- instances for CronSchedule from package `cron`
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instance Cacheable StepField
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instance Cacheable RangeField
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instance Cacheable SpecificField
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instance Cacheable BaseField
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instance Cacheable CronField
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instance Cacheable MonthSpec
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instance Cacheable DayOfMonthSpec
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instance Cacheable DayOfWeekSpec
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instance Cacheable HourSpec
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instance Cacheable MinuteSpec
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instance Cacheable CronSchedule
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instance (Cacheable a) => Cacheable (Seq a) where
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unchanged = liftEq . unchanged
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instance (Cacheable a) => Cacheable (Vector a) where
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unchanged = liftEq . unchanged
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instance (Cacheable k, Cacheable v) => Cacheable (HashMap k v) where
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unchanged accesses = liftEq2 (unchanged accesses) (unchanged accesses)
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instance (Cacheable a) => Cacheable (HashSet a) where
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unchanged = liftEq . unchanged
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instance (Cacheable a) => Cacheable (CI a) where
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unchanged _ = (==)
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instance (Cacheable a) => Cacheable (Set a) where
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unchanged = liftEq . unchanged
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instance (Hashable k, Cacheable k, Cacheable v) => Cacheable (InsOrdHashMap k v) where
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unchanged accesses l r = unchanged accesses (toHashMap l) (toHashMap r)
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where
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toHashMap = Map.fromList . OMap.toList
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instance Cacheable ()
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instance (Cacheable a, Cacheable b) => Cacheable (a, b)
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instance (Cacheable a, Cacheable b, Cacheable c) => Cacheable (a, b, c)
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instance (Cacheable a, Cacheable b, Cacheable c, Cacheable d) => Cacheable (a, b, c, d)
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instance (Cacheable a, Cacheable b, Cacheable c, Cacheable d, Cacheable e) => Cacheable (a, b, c, d, e)
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instance (Cacheable a, Cacheable b, Cacheable c, Cacheable d, Cacheable e, Cacheable f) => Cacheable (a, b, c, d, e, f)
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instance Cacheable Bool
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instance Cacheable Void
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instance Cacheable Value
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instance Cacheable G.FragmentDefinition
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instance Cacheable G.GType
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instance Cacheable G.Nullability
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instance Cacheable G.OperationType
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instance Cacheable G.VariableDefinition
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instance Cacheable G.InputValueDefinition
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instance Cacheable G.EnumValueDefinition
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instance (Cacheable a) => Cacheable (G.FieldDefinition a)
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instance Cacheable G.ScalarTypeDefinition
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instance Cacheable G.UnionTypeDefinition
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instance (Cacheable possibleTypes, Cacheable a) => Cacheable (G.InterfaceTypeDefinition a possibleTypes)
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instance Cacheable G.EnumTypeDefinition
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instance (Cacheable a) => Cacheable (G.InputObjectTypeDefinition a)
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instance (Cacheable a) => Cacheable (G.ObjectTypeDefinition a)
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instance (Cacheable a, Cacheable possibleTypes) => Cacheable (G.TypeDefinition a possibleTypes)
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instance Cacheable N.URI
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instance Cacheable UT.Variable
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instance Cacheable UT.TemplateItem
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instance Cacheable UT.URLTemplate
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instance (Cacheable a) => Cacheable (Maybe a)
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instance (Cacheable a, Cacheable b) => Cacheable (Either a b)
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instance (Cacheable a) => Cacheable (NESeq a)
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instance Cacheable a => Cacheable [a]
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instance Cacheable a => Cacheable (NonEmpty a)
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instance Cacheable a => Cacheable (G.Directive a)
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instance Cacheable a => Cacheable (G.ExecutableDefinition a)
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instance (Cacheable (a b), Cacheable b) => Cacheable (G.Field a b)
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instance Cacheable a => Cacheable (G.FragmentSpread a)
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instance (Cacheable (a b), Cacheable b) => Cacheable (G.InlineFragment a b)
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instance (Cacheable (a b), Cacheable b) => Cacheable (G.OperationDefinition a b)
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instance (Cacheable (a b), Cacheable b) => Cacheable (G.Selection a b)
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instance (Cacheable (a b), Cacheable b) => Cacheable (G.TypedOperationDefinition a b)
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instance Cacheable a => Cacheable (G.Value a)
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instance Cacheable a => Cacheable (Const a b)
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deriving instance Cacheable G.Description
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deriving instance Cacheable G.EnumValue
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deriving instance Cacheable a => Cacheable (G.ExecutableDocument a)
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instance Cacheable G.RootOperationTypeDefinition
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instance Cacheable G.SchemaDefinition
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instance Cacheable G.TypeSystemDefinition
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instance Cacheable G.SchemaDocument
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instance Cacheable G.SchemaIntrospection
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class GCacheable f where
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gunchanged :: f p -> f p -> Accesses -> Bool
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instance GCacheable V1 where
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gunchanged a = case a of {}
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{-# INLINE gunchanged #-}
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instance GCacheable U1 where
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gunchanged U1 U1 _ = True
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{-# INLINE gunchanged #-}
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instance (Cacheable a) => GCacheable (K1 t a) where
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gunchanged (K1 a) (K1 b) accesses = unchanged accesses a b
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{-# INLINE gunchanged #-}
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instance (GCacheable f) => GCacheable (M1 t m f) where
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gunchanged (M1 a) (M1 b) = gunchanged a b
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{-# INLINE gunchanged #-}
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instance (GCacheable f, GCacheable g) => GCacheable (f :*: g) where
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gunchanged (a1 :*: a2) (b1 :*: b2) = liftA2 (&&) (gunchanged a1 b1) (gunchanged a2 b2)
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{-# INLINE gunchanged #-}
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instance (GCacheable f, GCacheable g) => GCacheable (f :+: g) where
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gunchanged (L1 a) (L1 b) = gunchanged a b
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gunchanged (R1 a) (R1 b) = gunchanged a b
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gunchanged _ _ = const False
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{-# INLINE gunchanged #-}
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