graphql-engine/server/src-lib/Hasura/RQL/DDL/Schema/Cache/Common.hs
Auke Booij cdac24c79f server: delete the Cacheable type class in favor of Eq
What is the `Cacheable` type class about?
```haskell
class Eq a => Cacheable a where
  unchanged :: Accesses -> a -> a -> Bool
  default unchanged :: (Generic a, GCacheable (Rep a)) => Accesses -> a -> a -> Bool
  unchanged accesses a b = gunchanged (from a) (from b) accesses
```
Its only method is an alternative to `(==)`. The added value of `unchanged` (and the additional `Accesses` argument) arises _only_ for one type, namely `Dependency`. Indeed, the `Cacheable (Dependency a)` instance is non-trivial, whereas every other `Cacheable` instance is completely boilerplate (and indeed either generated from `Generic`, or simply `unchanged _ = (==)`). The `Cacheable (Dependency a)` instance is the only one where the `Accesses` argument is not just passed onwards.

The only callsite of the `unchanged` method is in the `ArrowCache (Rule m)` method. That is to say that the `Cacheable` type class is used to decide when we can re-use parts of the schema cache between Metadata operations.

So what is the `Cacheable (Dependency a)` instance about? Normally, the output of a `Rule m a b` is re-used when the new input (of type `a`) is equal to the old one. But sometimes, that's too coarse: it might be that a certain `Rule m a b` only depends on a small part of its input of type `a`. A `Dependency` allows us to spell out what parts of `a` are being depended on, and these parts are recorded as values of types `Access a` in the state `Accesses`.

If the input `a` changes, but not in a way that touches the recorded `Accesses`, then the output `b` of that rule can be re-used without recomputing.

So now you understand _why_ we're passing `Accesses` to the `unchanged` method: `unchanged` is an equality check in disguise that just needs some additional context.

But we don't need to pass `Accesses` as a function argument. We can use the `reflection` package to pass it as type-level context. So the core of this PR is that we change the instance declaration from
```haskell
instance (Cacheable a) => Cacheable (Dependency a) where
```
to
```haskell
 instance (Given Accesses, Eq a) => Eq (Dependency a) where
```
and use `(==)` instead of `unchanged`.

If you haven't seen `reflection` before: it's like a `MonadReader`, but it doesn't require a `Monad`.

In order to pass the current `Accesses` value, instead of simply passing the `Accesses` as a function argument, we need to instantiate the `Given Accesses` context. We use the `give` method from the `reflection` package for that.
```haskell
give :: forall r. Accesses -> (Given Accesses => r) -> r

unchanged :: (Given Accesses => Eq a) => Accesses -> a -> a -> Bool
unchanged accesses a b = give accesses (a == b)
```
With these three components in place, we can delete the `Cacheable` type class entirely.

The remainder of this PR is just to remove the `Cacheable` type class and its instances.

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6877
GitOrigin-RevId: 7125f5e11d856e7672ab810a23d5bf5ad176e77f
2022-11-21 16:35:37 +00:00

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{-# LANGUAGE Arrows #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE UndecidableInstances #-}
-- | Types/functions shared between modules that implement "Hasura.RQL.DDL.Schema.Cache". Other
-- modules should not import this module directly.
module Hasura.RQL.DDL.Schema.Cache.Common
( ApolloFederationConfig (..),
ApolloFederationVersion (..),
BackendInvalidationKeysWrapper (..),
BuildOutputs (..),
CacheBuild,
CacheBuildParams (CacheBuildParams),
InvalidationKeys (..),
ikMetadata,
ikRemoteSchemas,
ikSources,
ikBackends,
NonColumnTableInputs (..),
RebuildableSchemaCache (RebuildableSchemaCache, lastBuiltSchemaCache),
TableBuildInput (TableBuildInput, _tbiName),
TablePermissionInputs (..),
addTableContext,
bindErrorA,
boActions,
boCronTriggers,
boCustomTypes,
boBackendCache,
boEndpoints,
boOpenTelemetryInfo,
boRemoteSchemas,
boRoles,
boSources,
buildInfoMap,
buildInfoMapPreservingMetadata,
initialInvalidationKeys,
invalidateKeys,
mkTableInputs,
runCacheBuild,
runCacheBuildM,
withRecordDependencies,
)
where
import Control.Arrow.Extended
import Control.Arrow.Interpret
import Control.Lens
import Control.Monad.Trans.Control (MonadBaseControl)
import Control.Monad.Unique
import Data.HashMap.Strict.Extended qualified as M
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.Sequence qualified as Seq
import Data.Text.Extended
import Hasura.Base.Error
import Hasura.Incremental qualified as Inc
import Hasura.Prelude
import Hasura.RQL.Types.Backend
import Hasura.RQL.Types.Common
import Hasura.RQL.Types.CustomTypes
import Hasura.RQL.Types.Endpoint
import Hasura.RQL.Types.EventTrigger
import Hasura.RQL.Types.Metadata
import Hasura.RQL.Types.Metadata.Backend (BackendMetadata (..))
import Hasura.RQL.Types.Metadata.Instances ()
import Hasura.RQL.Types.Metadata.Object
import Hasura.RQL.Types.OpenTelemetry (OpenTelemetryInfo)
import Hasura.RQL.Types.Permission
import Hasura.RQL.Types.QueryCollection
import Hasura.RQL.Types.Relationships.Local
import Hasura.RQL.Types.Relationships.Remote
import Hasura.RQL.Types.Roles
import Hasura.RQL.Types.SchemaCache
import Hasura.RQL.Types.SchemaCache.Build
import Hasura.RQL.Types.Source
import Hasura.RemoteSchema.Metadata
import Hasura.SQL.Backend
import Hasura.SQL.BackendMap (BackendMap)
import Hasura.SQL.BackendMap qualified as BackendMap
import Hasura.Server.Types
import Hasura.Session
import Network.HTTP.Client.Manager (HasHttpManagerM (..))
import Network.HTTP.Client.Transformable qualified as HTTP
newtype BackendInvalidationKeysWrapper (b :: BackendType) = BackendInvalidationKeysWrapper
{ unBackendInvalidationKeysWrapper :: BackendInvalidationKeys b
}
deriving newtype instance Eq (BackendInvalidationKeys b) => Eq (BackendInvalidationKeysWrapper b)
deriving newtype instance Ord (BackendInvalidationKeys b) => Ord (BackendInvalidationKeysWrapper b)
deriving newtype instance Show (BackendInvalidationKeys b) => Show (BackendInvalidationKeysWrapper b)
deriving newtype instance Semigroup (BackendInvalidationKeys b) => Semigroup (BackendInvalidationKeysWrapper b)
deriving newtype instance Monoid (BackendInvalidationKeys b) => Monoid (BackendInvalidationKeysWrapper b)
instance Inc.Select (BackendInvalidationKeysWrapper b)
-- | 'InvalidationKeys' used to apply requested 'CacheInvalidations'.
data InvalidationKeys = InvalidationKeys
{ _ikMetadata :: Inc.InvalidationKey,
_ikRemoteSchemas :: HashMap RemoteSchemaName Inc.InvalidationKey,
_ikSources :: HashMap SourceName Inc.InvalidationKey,
_ikBackends :: BackendMap BackendInvalidationKeysWrapper
}
deriving (Show, Eq, Generic)
instance Inc.Select InvalidationKeys
$(makeLenses ''InvalidationKeys)
initialInvalidationKeys :: InvalidationKeys
initialInvalidationKeys = InvalidationKeys Inc.initialInvalidationKey mempty mempty mempty
invalidateKeys :: CacheInvalidations -> InvalidationKeys -> InvalidationKeys
invalidateKeys CacheInvalidations {..} InvalidationKeys {..} =
InvalidationKeys
{ _ikMetadata = if ciMetadata then Inc.invalidate _ikMetadata else _ikMetadata,
_ikRemoteSchemas = foldl' (flip invalidate) _ikRemoteSchemas ciRemoteSchemas,
_ikSources = foldl' (flip invalidate) _ikSources ciSources,
_ikBackends = BackendMap.modify @'DataConnector invalidateDataConnectors _ikBackends
}
where
invalidate ::
Hashable a =>
a ->
HashMap a Inc.InvalidationKey ->
HashMap a Inc.InvalidationKey
invalidate = M.alter $ Just . maybe Inc.initialInvalidationKey Inc.invalidate
invalidateDataConnectors :: BackendInvalidationKeysWrapper 'DataConnector -> BackendInvalidationKeysWrapper 'DataConnector
invalidateDataConnectors (BackendInvalidationKeysWrapper invalidationKeys) =
BackendInvalidationKeysWrapper $ foldl' (flip invalidate) invalidationKeys ciDataConnectors
data TableBuildInput b = TableBuildInput
{ _tbiName :: TableName b,
_tbiIsEnum :: Bool,
_tbiConfiguration :: TableConfig b,
_tbiApolloFederationConfig :: Maybe ApolloFederationConfig
}
deriving (Show, Eq, Generic)
instance (Backend b) => NFData (TableBuildInput b)
data NonColumnTableInputs b = NonColumnTableInputs
{ _nctiTable :: TableName b,
_nctiObjectRelationships :: [ObjRelDef b],
_nctiArrayRelationships :: [ArrRelDef b],
_nctiComputedFields :: [ComputedFieldMetadata b],
_nctiRemoteRelationships :: [RemoteRelationship]
}
deriving (Show, Eq, Generic)
data TablePermissionInputs b = TablePermissionInputs
{ _tpiTable :: TableName b,
_tpiInsert :: [InsPermDef b],
_tpiSelect :: [SelPermDef b],
_tpiUpdate :: [UpdPermDef b],
_tpiDelete :: [DelPermDef b]
}
deriving (Generic)
deriving instance (Backend b) => Show (TablePermissionInputs b)
deriving instance (Backend b) => Eq (TablePermissionInputs b)
mkTableInputs ::
TableMetadata b -> (TableBuildInput b, NonColumnTableInputs b, TablePermissionInputs b)
mkTableInputs TableMetadata {..} =
(buildInput, nonColumns, permissions)
where
buildInput = TableBuildInput _tmTable _tmIsEnum _tmConfiguration _tmApolloFederationConfig
nonColumns =
NonColumnTableInputs
_tmTable
(OMap.elems _tmObjectRelationships)
(OMap.elems _tmArrayRelationships)
(OMap.elems _tmComputedFields)
(OMap.elems _tmRemoteRelationships)
permissions =
TablePermissionInputs
_tmTable
(OMap.elems _tmInsertPermissions)
(OMap.elems _tmSelectPermissions)
(OMap.elems _tmUpdatePermissions)
(OMap.elems _tmDeletePermissions)
-- | The direct output of 'buildSchemaCacheRule'. Contains most of the things necessary to build a
-- schema cache, but dependencies and inconsistent metadata objects are collected via a separate
-- 'MonadWriter' side channel.
data BuildOutputs = BuildOutputs
{ _boSources :: SourceCache,
_boActions :: ActionCache,
-- | We preserve the 'MetadataObject' from the original catalog metadata in the output so we can
-- reuse it later if we need to mark the remote schema inconsistent during GraphQL schema
-- generation (because of field conflicts).
_boRemoteSchemas :: HashMap RemoteSchemaName (RemoteSchemaCtx, MetadataObject),
_boCustomTypes :: AnnotatedCustomTypes,
_boCronTriggers :: M.HashMap TriggerName CronTriggerInfo,
_boEndpoints :: M.HashMap EndpointName (EndpointMetadata GQLQueryWithText),
_boRoles :: HashMap RoleName Role,
_boBackendCache :: BackendCache,
_boOpenTelemetryInfo :: OpenTelemetryInfo
}
$(makeLenses ''BuildOutputs)
-- | Parameters required for schema cache build
data CacheBuildParams = CacheBuildParams
{ _cbpManager :: HTTP.Manager,
_cbpPGSourceResolver :: SourceResolver ('Postgres 'Vanilla),
_cbpMSSQLSourceResolver :: SourceResolver 'MSSQL,
_cbpServerConfigCtx :: ServerConfigCtx
}
-- | The monad in which @'RebuildableSchemaCache' is being run
newtype CacheBuild a = CacheBuild (ReaderT CacheBuildParams (ExceptT QErr IO) a)
deriving
( Functor,
Applicative,
Monad,
MonadError QErr,
MonadReader CacheBuildParams,
MonadIO,
MonadBase IO,
MonadBaseControl IO,
MonadUnique
)
instance HasHttpManagerM CacheBuild where
askHttpManager = asks _cbpManager
instance HasServerConfigCtx CacheBuild where
askServerConfigCtx = asks _cbpServerConfigCtx
instance MonadResolveSource CacheBuild where
getPGSourceResolver = asks _cbpPGSourceResolver
getMSSQLSourceResolver = asks _cbpMSSQLSourceResolver
runCacheBuild ::
( MonadIO m,
MonadError QErr m
) =>
CacheBuildParams ->
CacheBuild a ->
m a
runCacheBuild params (CacheBuild m) = do
liftEitherM $ liftIO $ runExceptT (runReaderT m params)
runCacheBuildM ::
( MonadIO m,
MonadError QErr m,
HasHttpManagerM m,
HasServerConfigCtx m,
MonadResolveSource m
) =>
CacheBuild a ->
m a
runCacheBuildM m = do
params <-
CacheBuildParams
<$> askHttpManager
<*> getPGSourceResolver
<*> getMSSQLSourceResolver
<*> askServerConfigCtx
runCacheBuild params m
data RebuildableSchemaCache = RebuildableSchemaCache
{ lastBuiltSchemaCache :: SchemaCache,
_rscInvalidationMap :: InvalidationKeys,
_rscRebuild :: Inc.Rule (ReaderT BuildReason CacheBuild) (Metadata, InvalidationKeys) SchemaCache
}
bindErrorA ::
(ArrowChoice arr, ArrowKleisli m arr, ArrowError e arr, MonadError e m) =>
arr (m a) a
bindErrorA = liftEitherA <<< arrM \m -> (Right <$> m) `catchError` (pure . Left)
{-# INLINE bindErrorA #-}
withRecordDependencies ::
(ArrowWriter (Seq (Either im MetadataDependency)) arr) =>
WriterA (Seq SchemaDependency) arr (e, s) a ->
arr (e, (MetadataObject, (SchemaObjId, s))) a
withRecordDependencies f = proc (e, (metadataObject, (schemaObjectId, s))) -> do
(result, dependencies) <- runWriterA f -< (e, s)
recordDependencies -< (metadataObject, schemaObjectId, toList dependencies)
returnA -< result
{-# INLINEABLE withRecordDependencies #-}
noDuplicates ::
(MonadWriter (Seq (Either InconsistentMetadata md)) m) =>
(a -> MetadataObject) ->
[a] ->
m (Maybe a)
noDuplicates mkMetadataObject = \case
[] -> pure Nothing
[value] -> pure $ Just value
values@(value : _) -> do
let objectId = _moId $ mkMetadataObject value
definitions = map (_moDefinition . mkMetadataObject) values
tell $ Seq.singleton $ Left (DuplicateObjects objectId definitions)
return Nothing
-- | Processes a list of catalog metadata into a map of processed information, marking any duplicate
-- entries inconsistent.
buildInfoMap ::
( ArrowChoice arr,
Inc.ArrowDistribute arr,
ArrowWriter (Seq (Either InconsistentMetadata md)) arr,
Hashable k
) =>
(a -> k) ->
(a -> MetadataObject) ->
(e, a) `arr` Maybe b ->
(e, [a]) `arr` HashMap k b
buildInfoMap extractKey mkMetadataObject buildInfo = proc (e, infos) -> do
let groupedInfos = M.groupOn extractKey infos
infoMapMaybes <-
(|
Inc.keyed
( \_ duplicateInfos -> do
infoMaybe <- interpretWriter -< noDuplicates mkMetadataObject duplicateInfos
case infoMaybe of
Nothing -> returnA -< Nothing
Just info -> buildInfo -< (e, info)
)
|) groupedInfos
returnA -< catMaybes infoMapMaybes
{-# INLINEABLE buildInfoMap #-}
-- | Like 'buildInfo', but includes each processed infos associated 'MetadataObject' in the result.
-- This is useful if the results will be further processed, and the 'MetadataObject' is still needed
-- to mark the object inconsistent.
buildInfoMapPreservingMetadata ::
( ArrowChoice arr,
Inc.ArrowDistribute arr,
ArrowWriter (Seq (Either InconsistentMetadata MetadataDependency)) arr,
Hashable k
) =>
(a -> k) ->
(a -> MetadataObject) ->
(e, a) `arr` Maybe b ->
(e, [a]) `arr` HashMap k (b, MetadataObject)
buildInfoMapPreservingMetadata extractKey mkMetadataObject buildInfo =
buildInfoMap extractKey mkMetadataObject buildInfoPreserving
where
buildInfoPreserving = proc (e, info) -> do
result <- buildInfo -< (e, info)
returnA -< result <&> (,mkMetadataObject info)
{-# INLINEABLE buildInfoMapPreservingMetadata #-}
addTableContext :: (Backend b) => TableName b -> Text -> Text
addTableContext tableName e = "in table " <> tableName <<> ": " <> e