Merge pull request #3798 from lexi-lambda/3759-3791-minor-metadata-build-bugfixes

Fix two minor bugs in the schema cache build process (fix #3759 and #3791)

server/src-exec/Main.hs

@@ -46,7 +46,7 @@ runApp (HGEOptionsG rci hgeCmd) =
         execQuery queryBs
           & runHasSystemDefinedT (SystemDefined False)
           & runCacheRWT schemaCache
-          & fmap fst
+          & fmap (\(res, _, _) -> res)
       either printErrJExit (liftIO . BLC.putStrLn) res
 
     HCVersion -> liftIO $ putStrLn $ "Hasura GraphQL Engine: " ++ convertText currentVersion

server/src-lib/Hasura/Incremental.hs

@@ -1,27 +1,51 @@
 -- | A simple implementation of /incremental build rules/, which can be used to avoid unnecessary
 -- recomputation on incrementally-changing input. See 'Rule' for more details.
-module Hasura.Incremental
+module Hasura.Incremental (
-  ( Rule
+  -- * The @Rule@ datatype
+    Rule
   , Result
   , build
   , rebuild
   , rebuildRule
   , result
 
+  -- * Abstract interface
   , ArrowDistribute(..)
   , ArrowCache(..)
   , MonadDepend(..)
   , DependT
 
+  -- * Fine-grained dependencies
   , Dependency
-  , Selector
+  , Select(Selector)
   , selectD
   , selectKeyD
   , Cacheable(..)
   , Accesses
+
+  -- * Cache invalidation
+  , InvalidationKey
+  , initialInvalidationKey
+  , invalidate
   ) where
 
+import           Hasura.Prelude
+
 import           Hasura.Incremental.Internal.Cache
 import           Hasura.Incremental.Internal.Dependency
 import           Hasura.Incremental.Internal.Rule
 import           Hasura.Incremental.Select
+
+-- | A simple helper type that can be used to implement explicit cache invalidation. Internally,
+-- each 'InvalidationKey' is a counter; 'initialInvalidationKey' starts the counter at 0 and
+-- 'invalidate' increments it by 1. Two 'InvalidationKey's are equal iff they have the same internal
+-- count, so depending on an 'InvalidationKey' provides a mechanism to force portions of the build
+-- process to be reexecuted by calling 'invalidate' before running the build.
+newtype InvalidationKey = InvalidationKey Int
+  deriving (Show, Eq, Cacheable)
+
+initialInvalidationKey :: InvalidationKey
+initialInvalidationKey = InvalidationKey 0
+
+invalidate :: InvalidationKey -> InvalidationKey
+invalidate (InvalidationKey n) = InvalidationKey (n + 1)

server/src-lib/Hasura/Incremental/Select.hs

@@ -6,6 +6,7 @@ module Hasura.Incremental.Select
   ( Select(..)
   , ConstS(..)
   , selectKey
+  , FieldS(..)
   , UniqueS
   , newUniqueS
   , DMapS(..)
@@ -25,6 +26,10 @@ import qualified Data.HashMap.Strict  as M
 import           Control.Monad.Unique
 import           Data.GADT.Compare
 import           Data.Kind
+import           Data.Proxy           (Proxy (..))
+import           GHC.OverloadedLabels (IsLabel (..))
+import           GHC.Records          (HasField (..))
+import           GHC.TypeLits         (KnownSymbol, sameSymbol, symbolVal)
 import           Unsafe.Coerce        (unsafeCoerce)
 
 -- | The 'Select' class provides a way to access subparts of a product type using a reified
@@ -34,10 +39,18 @@ import           Unsafe.Coerce        (unsafeCoerce)
 --
 -- This is useful to implement dependency tracking, since it’s possible to track in a reified form
 -- exactly which parts of a data structure are used.
+--
+-- Instances of 'Select' can be automatically derived for record types (just define an empty
+-- instance). The instance uses the magical 'HasField' constraints, and 'Selector's for the type can
+-- be written using @OverloadedLabels@.
 class (GCompare (Selector a)) => Select a where
   type Selector a :: Type -> Type
   select :: Selector a b -> a -> b
 
+  type Selector r = FieldS r
+  default select :: Selector a ~ FieldS a => Selector a b -> a -> b
+  select (FieldS (_ :: Proxy s)) = getField @s
+
 instance (Eq k, Ord k, Hashable k) => Select (HashMap k v) where
   type Selector (HashMap k v) = ConstS k (Maybe v)
   select (ConstS k) = M.lookup k
@@ -66,6 +79,29 @@ instance (Ord k) => GCompare (ConstS k a) where
     EQ -> GEQ
     GT -> GGT
 
+data FieldS r a where
+  FieldS :: (KnownSymbol s, HasField s r a) => !(Proxy s) -> FieldS r a
+
+instance (KnownSymbol s, HasField s r a) => IsLabel s (FieldS r a) where
+  fromLabel = FieldS (Proxy @s)
+
+instance GEq (FieldS r) where
+  FieldS a `geq` FieldS b = case sameSymbol a b of
+    -- If two fields of the same record have the same name, then their fields fundamentally must
+    -- have the same type! However, unfortunately, `HasField` constraints use a functional
+    -- dependency to enforce this rather than a type family, and functional dependencies don’t
+    -- provide evidence, so we have to use `unsafeCoerce` here. Yuck!
+    Just Refl -> Just (unsafeCoerce Refl)
+    Nothing   -> Nothing
+
+instance GCompare (FieldS r) where
+  FieldS a `gcompare` FieldS b = case sameSymbol a b of
+    -- See note about `HasField` and `unsafeCoerce` above.
+    Just Refl -> unsafeCoerce GEQ
+    Nothing
+      | symbolVal a < symbolVal b -> GLT
+      | otherwise -> GGT
+
 -- | A 'UniqueS' is, as the name implies, a globally-unique 'Selector', which can be created using
 -- 'newUniqueS'. If a value of type @'UniqueS' a@ is found to be equal (via 'geq') with another
 -- value of type @'UniqueS' b@, then @a@ and @b@ must be the same type. This effectively allows the

server/src-lib/Hasura/RQL/DDL/Metadata.hs

@@ -380,7 +380,7 @@ runExportMetadata _ =
 
 runReloadMetadata :: (QErrM m, CacheRWM m) => ReloadMetadata -> m EncJSON
 runReloadMetadata ReloadMetadata = do
-  buildSchemaCache
+  buildSchemaCacheWithOptions CatalogUpdate mempty { ciMetadata = True }
   return successMsg
 
 runDumpInternalState

server/src-lib/Hasura/RQL/DDL/RemoteSchema.hs

@@ -13,6 +13,7 @@ import           Hasura.Prelude
 
 import qualified Data.Aeson                  as J
 import qualified Data.HashMap.Strict         as Map
+import qualified Data.HashSet                as S
 import qualified Database.PG.Query           as Q
 
 import           Hasura.GraphQL.RemoteServer
@@ -87,8 +88,8 @@ runReloadRemoteSchema (RemoteSchemaNameQuery name) = do
   void $ onNothing (Map.lookup name rmSchemas) $
     throw400 NotExists $ "remote schema with name " <> name <<> " does not exist"
 
-  invalidateCachedRemoteSchema name
+  let invalidations = mempty { ciRemoteSchemas = S.singleton name }
-  withNewInconsistentObjsCheck buildSchemaCache
+  withNewInconsistentObjsCheck $ buildSchemaCacheWithOptions CatalogUpdate invalidations
   pure successMsg
 
 addRemoteSchemaToCatalog

server/src-lib/Hasura/RQL/DDL/Schema/Cache.hs

@@ -1,4 +1,5 @@
-{-# LANGUAGE Arrows #-}
+{-# LANGUAGE Arrows           #-}
+{-# LANGUAGE OverloadedLabels #-}
 
 {-| Top-level functions concerned specifically with operations on the schema cache, such as
 rebuilding it from the catalog and incorporating schema changes. See the module documentation for
@@ -60,75 +61,97 @@ buildRebuildableSchemaCache
   => m (RebuildableSchemaCache m)
 buildRebuildableSchemaCache = do
   catalogMetadata <- liftTx fetchCatalogData
-  result <- flip runReaderT CatalogSync $ Inc.build buildSchemaCacheRule (catalogMetadata, M.empty)
+  result <- flip runReaderT CatalogSync $
-  pure $ RebuildableSchemaCache (Inc.result result) M.empty (Inc.rebuildRule result)
+    Inc.build buildSchemaCacheRule (catalogMetadata, initialInvalidationKeys)
+  pure $ RebuildableSchemaCache (Inc.result result) initialInvalidationKeys (Inc.rebuildRule result)
 
 newtype CacheRWT m a
-  = CacheRWT { unCacheRWT :: StateT (RebuildableSchemaCache m) m a }
+  -- The CacheInvalidations component of the state could actually be collected using WriterT, but
+  -- WriterT implementations prior to transformers-0.5.6.0 (which added
+  -- Control.Monad.Trans.Writer.CPS) are leaky, and we don’t have that yet.
+  = CacheRWT (StateT (RebuildableSchemaCache m, CacheInvalidations) m a)
   deriving
-    ( Functor, Applicative, Monad, MonadIO, MonadReader r, MonadError e, MonadWriter w, MonadTx
+    ( Functor, Applicative, Monad, MonadIO, MonadReader r, MonadError e, MonadTx
     , UserInfoM, HasHttpManager, HasSQLGenCtx, HasSystemDefined )
 
-runCacheRWT :: RebuildableSchemaCache m -> CacheRWT m a -> m (a, RebuildableSchemaCache m)
+runCacheRWT
-runCacheRWT cache = flip runStateT cache . unCacheRWT
+  :: Functor m
+  => RebuildableSchemaCache m -> CacheRWT m a -> m (a, RebuildableSchemaCache m, CacheInvalidations)
+runCacheRWT cache (CacheRWT m) =
+  runStateT m (cache, mempty) <&> \(v, (newCache, invalidations)) -> (v, newCache, invalidations)
 
 instance MonadTrans CacheRWT where
   lift = CacheRWT . lift
 
 instance (Monad m) => TableCoreInfoRM (CacheRWT m)
 instance (Monad m) => CacheRM (CacheRWT m) where
-  askSchemaCache = CacheRWT $ gets lastBuiltSchemaCache
+  askSchemaCache = CacheRWT $ gets (lastBuiltSchemaCache . fst)
 
-instance (MonadIO m, MonadTx m, MonadUnique m) => CacheRWM (CacheRWT m) where
+instance (MonadIO m, MonadTx m) => CacheRWM (CacheRWT m) where
-  buildSchemaCacheWithOptions buildReason = CacheRWT do
+  buildSchemaCacheWithOptions buildReason invalidations = CacheRWT do
-    RebuildableSchemaCache _ invalidationMap rule <- get
+    (RebuildableSchemaCache _ invalidationKeys rule, oldInvalidations) <- get
+    let newInvalidationKeys = invalidateKeys invalidations invalidationKeys
     catalogMetadata <- liftTx fetchCatalogData
-    result <- lift $ flip runReaderT buildReason $ Inc.build rule (catalogMetadata, invalidationMap)
+    result <- lift $ flip runReaderT buildReason $
+      Inc.build rule (catalogMetadata, newInvalidationKeys)
     let schemaCache = Inc.result result
-        prunedInvalidationMap = pruneInvalidationMap schemaCache invalidationMap
+        prunedInvalidationKeys = pruneInvalidationKeys schemaCache newInvalidationKeys
-    put $! RebuildableSchemaCache schemaCache prunedInvalidationMap (Inc.rebuildRule result)
+        !newCache = RebuildableSchemaCache schemaCache prunedInvalidationKeys (Inc.rebuildRule result)
+        !newInvalidations = oldInvalidations <> invalidations
+    put (newCache, newInvalidations)
     where
-      pruneInvalidationMap schemaCache = M.filterWithKey \name _ ->
+      -- Prunes invalidation keys that no longer exist in the schema to avoid leaking memory by
+      -- hanging onto unnecessary keys.
+      pruneInvalidationKeys schemaCache = over ikRemoteSchemas $ M.filterWithKey \name _ ->
         M.member name (scRemoteSchemas schemaCache)
 
-  invalidateCachedRemoteSchema name = CacheRWT do
-    unique <- newUnique
-    assign (rscInvalidationMap . at name) (Just unique)
-
 buildSchemaCacheRule
   -- Note: by supplying BuildReason via MonadReader, it does not participate in caching, which is
   -- what we want!
   :: ( HasVersion, ArrowChoice arr, Inc.ArrowDistribute arr, Inc.ArrowCache m arr
      , MonadIO m, MonadTx m, MonadReader BuildReason m, HasHttpManager m, HasSQLGenCtx m )
-  => (CatalogMetadata, InvalidationMap) `arr` SchemaCache
+  => (CatalogMetadata, InvalidationKeys) `arr` SchemaCache
-buildSchemaCacheRule = proc inputs -> do
+buildSchemaCacheRule = proc (catalogMetadata, invalidationKeys) -> do
-  (outputs, collectedInfo) <- runWriterA buildAndCollectInfo -< inputs
+  invalidationKeysDep <- Inc.newDependency -< invalidationKeys
+
+  -- Step 1: Process metadata and collect dependency information.
+  (outputs, collectedInfo) <-
+    runWriterA buildAndCollectInfo -< (catalogMetadata, invalidationKeysDep)
   let (inconsistentObjects, unresolvedDependencies) = partitionCollectedInfo collectedInfo
-  (resolvedOutputs, extraInconsistentObjects, resolvedDependencies) <-
+
+  -- Step 2: Resolve dependency information and drop dangling dependents.
+  (resolvedOutputs, dependencyInconsistentObjects, resolvedDependencies) <-
     resolveDependencies -< (outputs, unresolvedDependencies)
+
+  -- Step 3: Build the GraphQL schema.
+  ((remoteSchemaMap, gqlSchema, remoteGQLSchema), gqlSchemaInconsistentObjects)
+    <- runWriterA buildGQLSchema
+    -< (_boTables resolvedOutputs, _boFunctions resolvedOutputs, _boRemoteSchemas resolvedOutputs)
+
   returnA -< SchemaCache
     { scTables = _boTables resolvedOutputs
     , scFunctions = _boFunctions resolvedOutputs
-    , scRemoteSchemas = _boRemoteSchemas resolvedOutputs
+    , scRemoteSchemas = remoteSchemaMap
     , scAllowlist = _boAllowlist resolvedOutputs
-    , scGCtxMap = _boGCtxMap resolvedOutputs
+    , scGCtxMap = gqlSchema
-    , scDefaultRemoteGCtx = _boDefaultRemoteGCtx resolvedOutputs
+    , scDefaultRemoteGCtx = remoteGQLSchema
     , scDepMap = resolvedDependencies
-    , scInconsistentObjs = inconsistentObjects <> extraInconsistentObjects
+    , scInconsistentObjs =
+        inconsistentObjects <> dependencyInconsistentObjects <> toList gqlSchemaInconsistentObjects
     }
   where
     buildAndCollectInfo
-      :: ( HasVersion, ArrowChoice arr, Inc.ArrowDistribute arr, Inc.ArrowCache m arr
+      :: ( ArrowChoice arr, Inc.ArrowDistribute arr, Inc.ArrowCache m arr
          , ArrowWriter (Seq CollectedInfo) arr, MonadIO m, MonadTx m, MonadReader BuildReason m
          , HasHttpManager m, HasSQLGenCtx m )
-      => (CatalogMetadata, InvalidationMap) `arr` BuildOutputs
+      => (CatalogMetadata, Inc.Dependency InvalidationKeys) `arr` BuildOutputs
-    buildAndCollectInfo = proc (catalogMetadata, invalidationMap) -> do
+    buildAndCollectInfo = proc (catalogMetadata, invalidationKeys) -> do
       let CatalogMetadata tables relationships permissions
             eventTriggers remoteSchemas functions allowlistDefs
             computedFields = catalogMetadata
 
       -- tables
-      tableRawInfos <- buildTableCache -< tables
+      tableRawInfos <- buildTableCache -< (tables, Inc.selectD #_ikMetadata invalidationKeys)
 
       -- relationships and computed fields
       let relationshipsByTable = M.groupOn _crTable relationships
@@ -182,23 +205,15 @@ buildSchemaCacheRule = proc inputs -> do
             & map (queryWithoutTypeNames . getGQLQuery . _lqQuery)
             & HS.fromList
 
-      -- build GraphQL context with tables and functions
-      baseGQLSchema <- bindA -< GS.mkGCtxMap tableCache functionCache
-
       -- remote schemas
-      let invalidatedRemoteSchemas = flip map remoteSchemas \remoteSchema ->
+      let remoteSchemaInvalidationKeys = Inc.selectD #_ikRemoteSchemas invalidationKeys
-            (M.lookup (_arsqName remoteSchema) invalidationMap, remoteSchema)
+      remoteSchemaMap <- buildRemoteSchemas -< (remoteSchemaInvalidationKeys, remoteSchemas)
-      (remoteSchemaMap, gqlSchema, remoteGQLSchema) <-
-        (| foldlA' (\schemas schema -> (schemas, schema) >- addRemoteSchema)
-        |) (M.empty, baseGQLSchema, GC.emptyGCtx) invalidatedRemoteSchemas
 
       returnA -< BuildOutputs
         { _boTables = tableCache
         , _boFunctions = functionCache
         , _boRemoteSchemas = remoteSchemaMap
         , _boAllowlist = allowList
-        , _boGCtxMap = gqlSchema
-        , _boDefaultRemoteGCtx = remoteGQLSchema
         }
 
     mkEventTriggerMetadataObject (CatalogEventTrigger qt trn configuration) =
@@ -206,6 +221,9 @@ buildSchemaCacheRule = proc inputs -> do
           definition = object ["table" .= qt, "configuration" .= configuration]
       in MetadataObject objectId definition
 
+    mkRemoteSchemaMetadataObject remoteSchema =
+      MetadataObject (MORemoteSchema (_arsqName remoteSchema)) (toJSON remoteSchema)
+
     -- Given a map of table info, “folds in” another map of information, accumulating inconsistent
     -- metadata objects for any entries in the second map that don’t appear in the first map. This
     -- is used to “line up” the metadata for relationships, computed fields, permissions, etc. with
@@ -236,14 +254,7 @@ buildSchemaCacheRule = proc inputs -> do
       :: ( ArrowChoice arr, Inc.ArrowDistribute arr, ArrowWriter (Seq CollectedInfo) arr
          , Inc.ArrowCache m arr, MonadIO m, MonadTx m, MonadReader BuildReason m, HasSQLGenCtx m )
       => (TableCoreInfo, [CatalogEventTrigger]) `arr` EventTriggerInfoMap
-    buildTableEventTriggers = proc (tableInfo, eventTriggers) ->
+    buildTableEventTriggers = buildInfoMap _cetName mkEventTriggerMetadataObject buildEventTrigger
-      (\infos -> M.catMaybes infos >- returnA) <-<
-        (| Inc.keyed (\_ duplicateEventTriggers -> do
-             maybeEventTrigger <- noDuplicates mkEventTriggerMetadataObject -< duplicateEventTriggers
-             (\info -> join info >- returnA) <-<
-               (| traverseA (\eventTrigger -> buildEventTrigger -< (tableInfo, eventTrigger))
-               |) maybeEventTrigger)
-        |) (M.groupOn _cetName eventTriggers)
       where
         buildEventTrigger = proc (tableInfo, eventTrigger) -> do
           let CatalogEventTrigger qt trn configuration = eventTrigger
@@ -268,24 +279,48 @@ buildSchemaCacheRule = proc inputs -> do
               liftTx $ delTriggerQ triggerName -- executes DROP IF EXISTS.. sql
               mkAllTriggersQ triggerName tableName (M.elems tableColumns) triggerDefinition
 
-    addRemoteSchema
+    buildRemoteSchemas
-      :: ( HasVersion, ArrowChoice arr, ArrowWriter (Seq CollectedInfo) arr, ArrowKleisli m arr
+      :: ( ArrowChoice arr, Inc.ArrowDistribute arr, ArrowWriter (Seq CollectedInfo) arr
-         , MonadIO m, HasHttpManager m )
+         , Inc.ArrowCache m arr , MonadIO m, HasHttpManager m )
-      => ( (RemoteSchemaMap, GS.GCtxMap, GS.GCtx)
+      => ( Inc.Dependency (HashMap RemoteSchemaName Inc.InvalidationKey)
-         , (Maybe InvalidationKey, AddRemoteSchemaQuery)
+         , [AddRemoteSchemaQuery]
+         ) `arr` HashMap RemoteSchemaName (RemoteSchemaCtx, MetadataObject)
+    buildRemoteSchemas =
+      buildInfoMapPreservingMetadata _arsqName mkRemoteSchemaMetadataObject buildRemoteSchema
+      where
+        -- We want to cache this call because it fetches the remote schema over HTTP, and we don’t
+        -- want to re-run that if the remote schema definition hasn’t changed.
+        buildRemoteSchema = Inc.cache proc (invalidationKeys, remoteSchema) -> do
+          Inc.dependOn -< Inc.selectKeyD (_arsqName remoteSchema) invalidationKeys
+          (| withRecordInconsistency (liftEitherA <<< bindA -<
+               runExceptT $ addRemoteSchemaP2Setup remoteSchema)
+           |) (mkRemoteSchemaMetadataObject remoteSchema)
+
+    -- Builds the GraphQL schema and merges in remote schemas. This function is kind of gross, as
+    -- it’s possible for the remote schema merging to fail, at which point we have to mark them
+    -- inconsistent. This means we have to accumulate the consistent remote schemas as we go, in
+    -- addition to the built GraphQL context.
+    buildGQLSchema
+      :: ( ArrowChoice arr, ArrowWriter (Seq InconsistentMetadata) arr, ArrowKleisli m arr
+         , MonadError QErr m )
+      => ( TableCache
+         , FunctionCache
+         , HashMap RemoteSchemaName (RemoteSchemaCtx, MetadataObject)
          ) `arr` (RemoteSchemaMap, GS.GCtxMap, GS.GCtx)
-    addRemoteSchema = proc ((remoteSchemas, gCtxMap, defGCtx), (_, remoteSchema)) -> do
+    buildGQLSchema = proc (tableCache, functionCache, remoteSchemas) -> do
-      let name = _arsqName remoteSchema
+      baseGQLSchema <- bindA -< GS.mkGCtxMap tableCache functionCache
-      (| onNothingA (returnA -< (remoteSchemas, gCtxMap, defGCtx)) |) <-<
+      (| foldlA' (\(remoteSchemaMap, gqlSchemas, remoteGQLSchemas)
-         (| withRecordInconsistency (case M.lookup name remoteSchemas of
+                   (remoteSchemaName, (remoteSchema, metadataObject)) ->
-              Just _ -> throwA -< err400 AlreadyExists "duplicate definition for remote schema"
+           (| withRecordInconsistency (do
-              Nothing -> liftEitherA <<< bindA -< runExceptT do
+                let gqlSchema = convRemoteGCtx $ rscGCtx remoteSchema
-                rsCtx <- addRemoteSchemaP2Setup remoteSchema
+                mergedGQLSchemas <- bindErrorA -< mergeRemoteSchema gqlSchemas gqlSchema
-                let rGCtx = convRemoteGCtx $ rscGCtx rsCtx
+                mergedRemoteGQLSchemas <- bindErrorA -< mergeGCtx remoteGQLSchemas gqlSchema
-                mergedGCtxMap <- mergeRemoteSchema gCtxMap rGCtx
+                let mergedRemoteSchemaMap = M.insert remoteSchemaName remoteSchema remoteSchemaMap
-                mergedDefGCtx <- mergeGCtx defGCtx rGCtx
+                returnA -< (mergedRemoteSchemaMap, mergedGQLSchemas, mergedRemoteGQLSchemas))
-                pure (M.insert name rsCtx remoteSchemas, mergedGCtxMap, mergedDefGCtx))
+           |) metadataObject
-         |) (MetadataObject (MORemoteSchema name) (toJSON remoteSchema))
+           >-> (| onNothingA ((remoteSchemaMap, gqlSchemas, remoteGQLSchemas) >- returnA) |))
+       |) (M.empty, baseGQLSchema, GC.emptyGCtx) (M.toList remoteSchemas)
+
 
 -- | @'withMetadataCheck' cascade action@ runs @action@ and checks if the schema changed as a
 -- result. If it did, it checks to ensure the changes do not violate any integrity constraints, and

server/src-lib/Hasura/RQL/DDL/Schema/Cache/Common.hs

@@ -1,4 +1,5 @@
-{-# LANGUAGE Arrows #-}
+{-# LANGUAGE Arrows          #-}
+{-# LANGUAGE RecordWildCards #-}
 
 -- | Types/functions shared between modules that implement "Hasura.RQL.DDL.Schema.Cache". Other
 -- modules should not import this module directly.
@@ -6,14 +7,13 @@ module Hasura.RQL.DDL.Schema.Cache.Common where
 
 import           Hasura.Prelude
 
+import qualified Data.HashMap.Strict.Extended     as M
 import qualified Data.HashSet                     as HS
 import qualified Data.Sequence                    as Seq
 
 import           Control.Arrow.Extended
 import           Control.Lens
-import           Control.Monad.Unique
 
-import qualified Hasura.GraphQL.Context           as GC
 import qualified Hasura.Incremental               as Inc
 
 import           Hasura.RQL.Types
@@ -22,18 +22,30 @@ import           Hasura.RQL.Types.QueryCollection
 import           Hasura.RQL.Types.Run
 import           Hasura.SQL.Types
 
--- | A map used to explicitly invalidate part of the build cache, which is most useful for external
+-- | 'InvalidationKeys' used to apply requested 'CacheInvalidations'.
--- resources (currently only remote schemas). The 'InvalidationKey' values it contains are used as
+data InvalidationKeys = InvalidationKeys
--- inputs to build rules, so setting an entry to a fresh 'InvalidationKey' forces it to be
+  { _ikMetadata      :: !Inc.InvalidationKey
--- re-executed.
+  , _ikRemoteSchemas :: !(HashMap RemoteSchemaName Inc.InvalidationKey)
-type InvalidationMap = HashMap RemoteSchemaName InvalidationKey
+  } deriving (Eq, Generic)
-type InvalidationKey = Unique
+instance Inc.Cacheable InvalidationKeys
+instance Inc.Select InvalidationKeys
+$(makeLenses ''InvalidationKeys)
+
+initialInvalidationKeys :: InvalidationKeys
+initialInvalidationKeys = InvalidationKeys Inc.initialInvalidationKey mempty
+
+invalidateKeys :: CacheInvalidations -> InvalidationKeys -> InvalidationKeys
+invalidateKeys CacheInvalidations{..} InvalidationKeys{..} = InvalidationKeys
+  { _ikMetadata = if ciMetadata then Inc.invalidate _ikMetadata else _ikMetadata
+  , _ikRemoteSchemas = foldl' (flip invalidateRemoteSchema) _ikRemoteSchemas ciRemoteSchemas }
+  where
+    invalidateRemoteSchema = M.alter $ Just . maybe Inc.initialInvalidationKey Inc.invalidate
 
 data BuildInputs
   = BuildInputs
   { _biReason          :: !BuildReason
   , _biCatalogMetadata :: !CatalogMetadata
-  , _biInvalidationMap :: !InvalidationMap
+  , _biInvalidationMap :: !InvalidationKeys
   } deriving (Eq)
 
 -- | The direct output of 'buildSchemaCacheRule'. Contains most of the things necessary to build a
@@ -41,20 +53,21 @@ data BuildInputs
 -- 'MonadWriter' side channel.
 data BuildOutputs
   = BuildOutputs
-  { _boTables            :: !TableCache
+  { _boTables        :: !TableCache
-  , _boFunctions         :: !FunctionCache
+  , _boFunctions     :: !FunctionCache
-  , _boRemoteSchemas     :: !RemoteSchemaMap
+  , _boRemoteSchemas :: !(HashMap RemoteSchemaName (RemoteSchemaCtx, MetadataObject))
-  , _boAllowlist         :: !(HS.HashSet GQLQuery)
+  -- ^ We preserve the 'MetadataObject' from the original catalog metadata in the output so we can
-  , _boGCtxMap           :: !GC.GCtxMap
+  -- reuse it later if we need to mark the remote schema inconsistent during GraphQL schema
-  , _boDefaultRemoteGCtx :: !GC.GCtx
+  -- generation (because of field conflicts).
+  , _boAllowlist     :: !(HS.HashSet GQLQuery)
   } deriving (Show, Eq)
 $(makeLenses ''BuildOutputs)
 
 data RebuildableSchemaCache m
   = RebuildableSchemaCache
   { lastBuiltSchemaCache :: !SchemaCache
-  , _rscInvalidationMap :: !InvalidationMap
+  , _rscInvalidationMap :: !InvalidationKeys
-  , _rscRebuild :: !(Inc.Rule (ReaderT BuildReason m) (CatalogMetadata, InvalidationMap) SchemaCache)
+  , _rscRebuild :: !(Inc.Rule (ReaderT BuildReason m) (CatalogMetadata, InvalidationKeys) SchemaCache)
   }
 $(makeLenses ''RebuildableSchemaCache)
 
@@ -91,5 +104,38 @@ noDuplicates mkMetadataObject = proc values -> case values of
     returnA -< Nothing
 {-# INLINABLE noDuplicates #-}
 
+-- | 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 CollectedInfo) arr
+     , Eq k, Hashable k )
+  => (a -> k)
+  -> (a -> MetadataObject)
+  -> (e, a) `arr` Maybe b
+  -> (e, [a]) `arr` HashMap k b
+buildInfoMap extractKey mkMetadataObject buildInfo = proc (e, infos) ->
+      (M.groupOn extractKey infos >- returnA)
+  >-> (| Inc.keyed (\_ duplicateInfos ->
+               (duplicateInfos >- noDuplicates mkMetadataObject)
+           >-> (| traverseA (\info -> (e, info) >- buildInfo) |)
+           >-> (\info -> join info >- returnA)) |)
+  >-> (\infoMap -> M.catMaybes infoMap >- returnA)
+{-# INLINABLE buildInfoMap #-}
+
+-- | Like 'buildInfo', but includes each processed info’s 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 CollectedInfo) arr
+     , Eq k, 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 proc (e, info) ->
+    ((e, info) >- buildInfo) >-> \result -> result <&> (, mkMetadataObject info) >- returnA
+{-# INLINABLE buildInfoMapPreservingMetadata #-}
+
 addTableContext :: QualifiedTable -> Text -> Text
 addTableContext tableName e = "in table " <> tableName <<> ": " <> e

server/src-lib/Hasura/RQL/DDL/Schema/Cache/Fields.hs

@@ -34,31 +34,19 @@ addNonColumnFields
      , [CatalogComputedField]
      ) `arr` FieldInfoMap FieldInfo
 addNonColumnFields = proc (rawTableInfo, columns, relationships, computedFields) -> do
-  let foreignKeys = _tciForeignKeys <$> rawTableInfo
+  relationshipInfos
-  relationshipInfos <-
+    <- buildInfoMapPreservingMetadata _crRelName mkRelationshipMetadataObject buildRelationship
-    (| Inc.keyed (\_ relationshipsByName -> do
+    -< (_tciForeignKeys <$> rawTableInfo, relationships)
-         maybeRelationship <- noDuplicates mkRelationshipMetadataObject -< relationshipsByName
+  computedFieldInfos
-         (\info -> join info >- returnA) <-<
+    <- buildInfoMapPreservingMetadata
-           (| traverseA (\relationship -> do
+         (_afcName . _cccComputedField)
-                info <- buildRelationship -< (foreignKeys, relationship)
+         mkComputedFieldMetadataObject
-                returnA -< info <&> (, mkRelationshipMetadataObject relationship))
+         buildComputedField
-           |) maybeRelationship)
+    -< (HS.fromList $ M.keys rawTableInfo, computedFields)
-    |) (M.groupOn _crRelName relationships)
-
-  let trackedTableNames = HS.fromList $ M.keys rawTableInfo
-  computedFieldInfos <-
-    (| Inc.keyed (\_ computedFieldsByName -> do
-         maybeComputedField <- noDuplicates mkComputedFieldMetadataObject -< computedFieldsByName
-         (\info -> join info >- returnA) <-<
-           (| traverseA (\computedField -> do
-                info <- buildComputedField -< (trackedTableNames, computedField)
-                returnA -< info <&> (, mkComputedFieldMetadataObject computedField))
-           |) maybeComputedField)
-    |) (M.groupOn (_afcName . _cccComputedField) computedFields)
 
   let mapKey f = M.fromList . map (first f) . M.toList
-      relationshipFields = mapKey fromRel $ M.catMaybes relationshipInfos
+      relationshipFields = mapKey fromRel relationshipInfos
-      computedFieldFields = mapKey fromComputedField $ M.catMaybes computedFieldInfos
+      computedFieldFields = mapKey fromComputedField computedFieldInfos
 
   -- First, check for conflicts between non-column fields, since we can raise a better error
   -- message in terms of the two metadata objects that define them.

server/src-lib/Hasura/RQL/DDL/Schema/Table.hs

@@ -292,10 +292,14 @@ buildTableCache
   :: forall arr m
    . ( ArrowChoice arr, Inc.ArrowDistribute arr, ArrowWriter (Seq CollectedInfo) arr
      , Inc.ArrowCache m arr, MonadTx m )
-  => [CatalogTable] `arr` M.HashMap QualifiedTable TableRawInfo
+  => ( [CatalogTable]
-buildTableCache = Inc.cache proc catalogTables -> do
+     , Inc.Dependency Inc.InvalidationKey
+     ) `arr` M.HashMap QualifiedTable TableRawInfo
+buildTableCache = Inc.cache proc (catalogTables, reloadMetadataInvalidationKey) -> do
   rawTableInfos <-
-    (| Inc.keyed (| withTable (\tables -> buildRawTableInfo <<< noDuplicateTables -< tables) |)
+    (| Inc.keyed (| withTable (\tables
+         -> (tables, reloadMetadataInvalidationKey)
+         >- first noDuplicateTables >>> buildRawTableInfo) |)
     |) (M.groupOnNE _ctName catalogTables)
   let rawTableCache = M.catMaybes rawTableInfos
       enumTables = flip M.mapMaybe rawTableCache \rawTableInfo ->
@@ -314,8 +318,13 @@ buildTableCache = Inc.cache proc catalogTables -> do
       _           -> throwA -< err400 AlreadyExists "duplication definition for table"
 
     -- Step 1: Build the raw table cache from metadata information.
-    buildRawTableInfo :: ErrorA QErr arr CatalogTable (TableCoreInfoG PGRawColumnInfo PGCol)
+    buildRawTableInfo
-    buildRawTableInfo = Inc.cache proc (CatalogTable name systemDefined isEnum config maybeInfo) -> do
+      :: ErrorA QErr arr
+       ( CatalogTable
+       , Inc.Dependency Inc.InvalidationKey
+       ) (TableCoreInfoG PGRawColumnInfo PGCol)
+    buildRawTableInfo = Inc.cache proc (catalogTable, reloadMetadataInvalidationKey) -> do
+      let CatalogTable name systemDefined isEnum config maybeInfo = catalogTable
       catalogInfo <-
         (| onNothingA (throwA -<
              err400 NotExists $ "no such table/view exists in postgres: " <>> name)
@@ -326,7 +335,11 @@ buildTableCache = Inc.cache proc catalogTables -> do
           primaryKey = _ctiPrimaryKey catalogInfo
       rawPrimaryKey <- liftEitherA -< traverse (resolvePrimaryKeyColumns columnMap) primaryKey
       enumValues <- if isEnum
-        then bindErrorA -< Just <$> fetchAndValidateEnumValues name rawPrimaryKey columns
+        then do
+          -- We want to make sure we reload enum values whenever someone explicitly calls
+          -- `reload_metadata`.
+          Inc.dependOn -< reloadMetadataInvalidationKey
+          bindErrorA -< Just <$> fetchAndValidateEnumValues name rawPrimaryKey columns
         else returnA -< Nothing
 
       returnA -< TableCoreInfo

server/src-lib/Hasura/RQL/Types/RemoteSchema.hs

@@ -22,7 +22,7 @@ type UrlFromEnv = Text
 newtype RemoteSchemaName
   = RemoteSchemaName
   { unRemoteSchemaName :: NonEmptyText }
-  deriving ( Show, Eq, Lift, Hashable, J.ToJSON, J.ToJSONKey
+  deriving ( Show, Eq, Ord, Lift, Hashable, J.ToJSON, J.ToJSONKey
            , J.FromJSON, Q.ToPrepArg, Q.FromCol, DQuote, NFData
            , Generic, Cacheable, Arbitrary
            )

server/src-lib/Hasura/RQL/Types/SchemaCache/Build.hs

@@ -13,6 +13,7 @@ module Hasura.RQL.Types.SchemaCache.Build
 
   , CacheRWM(..)
   , BuildReason(..)
+  , CacheInvalidations(..)
   , buildSchemaCache
   , buildSchemaCacheFor
   , buildSchemaCacheStrict
@@ -26,7 +27,10 @@ import qualified Data.Sequence                 as Seq
 import qualified Data.Text                     as T
 
 import           Control.Arrow.Extended
+import           Control.Lens
 import           Data.Aeson                    (toJSON)
+import           Data.Aeson.Casing
+import           Data.Aeson.TH
 import           Data.List                     (nub)
 
 import           Hasura.RQL.Types.Error
@@ -44,6 +48,14 @@ data CollectedInfo
     !SchemaObjId
     !SchemaDependency
   deriving (Show, Eq)
+$(makePrisms ''CollectedInfo)
+
+class AsInconsistentMetadata s where
+  _InconsistentMetadata :: Prism' s InconsistentMetadata
+instance AsInconsistentMetadata InconsistentMetadata where
+  _InconsistentMetadata = id
+instance AsInconsistentMetadata CollectedInfo where
+  _InconsistentMetadata = _CIInconsistency
 
 partitionCollectedInfo
   :: Seq CollectedInfo
@@ -55,12 +67,14 @@ partitionCollectedInfo =
       let dependency = (metadataObject, objectId, schemaDependency)
       in (inconsistencies, dependency:dependencies)
 
-recordInconsistency :: (ArrowWriter (Seq CollectedInfo) arr) => (MetadataObject, Text) `arr` ()
+recordInconsistency
+  :: (ArrowWriter (Seq w) arr, AsInconsistentMetadata w) => (MetadataObject, Text) `arr` ()
 recordInconsistency = first (arr (:[])) >>> recordInconsistencies
 
-recordInconsistencies :: (ArrowWriter (Seq CollectedInfo) arr) => ([MetadataObject], Text) `arr` ()
+recordInconsistencies
+  :: (ArrowWriter (Seq w) arr, AsInconsistentMetadata w) => ([MetadataObject], Text) `arr` ()
 recordInconsistencies = proc (metadataObjects, reason) ->
-  tellA -< Seq.fromList $ map (CIInconsistency . InconsistentObject reason) metadataObjects
+  tellA -< Seq.fromList $ map (review _InconsistentMetadata . InconsistentObject reason) metadataObjects
 
 recordDependencies
   :: (ArrowWriter (Seq CollectedInfo) arr)
@@ -69,7 +83,7 @@ recordDependencies = proc (metadataObject, schemaObjectId, dependencies) ->
   tellA -< Seq.fromList $ map (CIDependency metadataObject schemaObjectId) dependencies
 
 withRecordInconsistency
-  :: (ArrowChoice arr, ArrowWriter (Seq CollectedInfo) arr)
+  :: (ArrowChoice arr, ArrowWriter (Seq w) arr, AsInconsistentMetadata w)
   => ErrorA QErr arr (e, s) a
   -> arr (e, (MetadataObject, s)) (Maybe a)
 withRecordInconsistency f = proc (e, (metadataObject, s)) -> do
@@ -85,8 +99,7 @@ withRecordInconsistency f = proc (e, (metadataObject, s)) -> do
 -- operations for triggering a schema cache rebuild
 
 class (CacheRM m) => CacheRWM m where
-  buildSchemaCacheWithOptions :: BuildReason -> m ()
+  buildSchemaCacheWithOptions :: BuildReason -> CacheInvalidations -> m ()
-  invalidateCachedRemoteSchema :: RemoteSchemaName -> m ()
 
 data BuildReason
   -- | The build was triggered by an update this instance made to the catalog (in the
@@ -99,12 +112,26 @@ data BuildReason
   | CatalogSync
   deriving (Show, Eq)
 
+data CacheInvalidations = CacheInvalidations
+  { ciMetadata      :: !Bool
+  -- ^ Force reloading of all database information, including information not technically stored in
+  -- metadata (currently just enum values). Set by the @reload_metadata@ API.
+  , ciRemoteSchemas :: !(HashSet RemoteSchemaName)
+  -- ^ Force refetching of the given remote schemas, even if their definition has not changed. Set
+  -- by the @reload_remote_schema@ API.
+  }
+$(deriveJSON (aesonDrop 2 snakeCase) ''CacheInvalidations)
+
+instance Semigroup CacheInvalidations where
+  CacheInvalidations a1 b1 <> CacheInvalidations a2 b2 = CacheInvalidations (a1 || a2) (b1 <> b2)
+instance Monoid CacheInvalidations where
+  mempty = CacheInvalidations False mempty
+
 instance (CacheRWM m) => CacheRWM (ReaderT r m) where
-  buildSchemaCacheWithOptions = lift . buildSchemaCacheWithOptions
+  buildSchemaCacheWithOptions a b = lift $ buildSchemaCacheWithOptions a b
-  invalidateCachedRemoteSchema = lift . invalidateCachedRemoteSchema
 
 buildSchemaCache :: (CacheRWM m) => m ()
-buildSchemaCache = buildSchemaCacheWithOptions CatalogUpdate
+buildSchemaCache = buildSchemaCacheWithOptions CatalogUpdate mempty
 
 -- | Rebuilds the schema cache. If an object with the given object id became newly inconsistent,
 -- raises an error about it specifically. Otherwise, raises a generic metadata inconsistency error.

server/src-lib/Hasura/Server/App.hs

@@ -5,6 +5,7 @@ module Hasura.Server.App where
 
 import           Control.Concurrent.MVar
 import           Control.Exception                      (IOException, try)
+import           Control.Lens                           (view, _2)
 import           Control.Monad.Stateless
 import           Data.Aeson                             hiding (json)
 import           Data.Either                            (isRight)
@@ -457,9 +458,9 @@ mkWaiApp isoLevel logger sqlGenCtx enableAL pool ci httpManager mode corsCfg ena
     (cacheRef, cacheBuiltTime) <- do
       pgResp <- runExceptT $ peelRun runCtx pgExecCtxSer Q.ReadWrite $
         (,) <$> buildRebuildableSchemaCache <*> liftTx fetchLastUpdate
-      (schemaCache, time) <- liftIO $ either initErrExit return pgResp
+      (schemaCache, event) <- liftIO $ either initErrExit return pgResp
       scRef <- liftIO $ newIORef (schemaCache, initSchemaCacheVer)
-      return (scRef, snd <$> time)
+      return (scRef, view _2 <$> event)
 
     cacheLock <- liftIO $ newMVar ()
     planCache <- liftIO $ E.initPlanCache planCacheOptions

server/src-lib/Hasura/Server/Migrate.hs

@@ -16,9 +16,6 @@ module Hasura.Server.Migrate
   , dropCatalog
   ) where
 
-import           Control.Monad.Unique
-import           Data.Time.Clock               (UTCTime)
-
 import           Hasura.Prelude
 
 import qualified Data.Aeson                    as A
@@ -29,6 +26,10 @@ import qualified Database.PG.Query.Connection  as Q
 import qualified Language.Haskell.TH.Lib       as TH
 import qualified Language.Haskell.TH.Syntax    as TH
 
+import           Control.Lens                  (view, _2)
+import           Control.Monad.Unique
+import           Data.Time.Clock               (UTCTime)
+
 import           Hasura.Logging                (Hasura, LogLevel (..), ToEngineLog (..))
 import           Hasura.RQL.DDL.Relationship
 import           Hasura.RQL.DDL.Schema
@@ -163,7 +164,7 @@ migrateCatalog migrationTime = do
     buildCacheAndRecreateSystemMetadata :: m (RebuildableSchemaCache m)
     buildCacheAndRecreateSystemMetadata = do
       schemaCache <- buildRebuildableSchemaCache
-      snd <$> runCacheRWT schemaCache recreateSystemMetadata
+      view _2 <$> runCacheRWT schemaCache recreateSystemMetadata
 
     -- the old 0.8 catalog version is non-integral, so we store it in the database as a string
     getCatalogVersion = liftTx $ runIdentity . Q.getRow <$> Q.withQE defaultTxErrorHandler

server/src-lib/Hasura/Server/Migrate/Version.hs

@@ -12,7 +12,7 @@ import           Hasura.Prelude
 import qualified Data.Text      as T
 
 latestCatalogVersion :: Integer
-latestCatalogVersion = 30
+latestCatalogVersion = 31
 
 latestCatalogVersionString :: T.Text
 latestCatalogVersionString = T.pack $ show latestCatalogVersion

server/src-lib/Hasura/Server/Query.hs

@@ -150,23 +150,21 @@ $(deriveJSON
   ''RQLQueryV2
  )
 
-fetchLastUpdate :: Q.TxE QErr (Maybe (InstanceId, UTCTime))
+fetchLastUpdate :: Q.TxE QErr (Maybe (InstanceId, UTCTime, CacheInvalidations))
-fetchLastUpdate = do
+fetchLastUpdate = over (_Just._3) Q.getAltJ <$> Q.withQE defaultTxErrorHandler [Q.sql|
-  Q.withQE defaultTxErrorHandler
+  SELECT instance_id::text, occurred_at, invalidations
-    [Q.sql|
+  FROM hdb_catalog.hdb_schema_update_event
-       SELECT instance_id::text, occurred_at
+  ORDER BY occurred_at DESC LIMIT 1
-       FROM hdb_catalog.hdb_schema_update_event
+  |] () True
-       ORDER BY occurred_at DESC LIMIT 1
-          |] () True
 
-recordSchemaUpdate :: InstanceId -> Q.TxE QErr ()
+recordSchemaUpdate :: InstanceId -> CacheInvalidations -> Q.TxE QErr ()
-recordSchemaUpdate instanceId =
+recordSchemaUpdate instanceId invalidations =
   liftTx $ Q.unitQE defaultTxErrorHandler [Q.sql|
              INSERT INTO hdb_catalog.hdb_schema_update_event
-               (instance_id, occurred_at) VALUES ($1::uuid, DEFAULT)
+               (instance_id, occurred_at, invalidations) VALUES ($1::uuid, DEFAULT, $2::json)
              ON CONFLICT ((occurred_at IS NOT NULL))
-             DO UPDATE SET instance_id = $1::uuid, occurred_at = DEFAULT
+             DO UPDATE SET instance_id = $1::uuid, occurred_at = DEFAULT, invalidations = $2::json
-            |] (Identity instanceId) True
+            |] (instanceId, Q.AltJ invalidations) True
 
 runQuery
   :: (HasVersion, MonadIO m, MonadError QErr m)
@@ -184,12 +182,12 @@ runQuery pgExecCtx instanceId userInfo sc hMgr sqlGenCtx systemDefined query = d
   either throwError withReload resE
   where
     runCtx = RunCtx userInfo hMgr sqlGenCtx
-    withReload r = do
+    withReload (result, updatedCache, invalidations) = do
       when (queryModifiesSchemaCache query) $ do
-        e <- liftIO $ runExceptT $ runLazyTx pgExecCtx Q.ReadWrite
+        e <- liftIO $ runExceptT $ runLazyTx pgExecCtx Q.ReadWrite $ liftTx $
-             $ liftTx $ recordSchemaUpdate instanceId
+          recordSchemaUpdate instanceId invalidations
         liftEither e
-      return r
+      return (result, updatedCache)
 
 -- | A predicate that determines whether the given query might modify/rebuild the schema cache. If
 -- so, it needs to acquire the global lock on the schema cache so that other queries do not modify

server/src-lib/Hasura/Server/SchemaUpdate.hs

@@ -58,9 +58,10 @@ instance ToEngineLog SchemaSyncThreadLog Hasura where
 
 data EventPayload
   = EventPayload
-  { _epInstanceId :: !InstanceId
+  { _epInstanceId    :: !InstanceId
-  , _epOccurredAt :: !UTC.UTCTime
+  , _epOccurredAt    :: !UTC.UTCTime
-  } deriving (Show, Eq)
+  , _epInvalidations :: !CacheInvalidations
+  }
 $(deriveJSON (aesonDrop 3 snakeCase) ''EventPayload)
 
 data ThreadError
@@ -136,9 +137,9 @@ listener sqlGenCtx pool logger httpMgr updateEventRef
         Just time -> (dbInstId /= instanceId) && accrdAt > time
 
     refreshCache Nothing = return ()
-    refreshCache (Just (dbInstId, accrdAt)) =
+    refreshCache (Just (dbInstId, accrdAt, invalidations)) =
       when (shouldRefresh dbInstId accrdAt) $
-        refreshSchemaCache sqlGenCtx pool logger httpMgr cacheRef
+        refreshSchemaCache sqlGenCtx pool logger httpMgr cacheRef invalidations
           threadType "schema cache reloaded after postgres listen init"
 
     notifyHandler = \case
@@ -179,7 +180,7 @@ processor sqlGenCtx pool logger httpMgr updateEventRef
     event <- STM.atomically getLatestEvent
     logInfo logger threadType $ object ["processed_event" .= event]
     when (shouldReload event) $
-      refreshSchemaCache sqlGenCtx pool logger httpMgr cacheRef
+      refreshSchemaCache sqlGenCtx pool logger httpMgr cacheRef (_epInvalidations event)
         threadType "schema cache reloaded"
   where
     -- checks if there is an event
@@ -202,15 +203,17 @@ refreshSchemaCache
   -> Logger Hasura
   -> HTTP.Manager
   -> SchemaCacheRef
+  -> CacheInvalidations
   -> ThreadType
   -> T.Text -> IO ()
-refreshSchemaCache sqlGenCtx pool logger httpManager cacheRef threadType msg = do
+refreshSchemaCache sqlGenCtx pool logger httpManager cacheRef invalidations threadType msg = do
   -- Reload schema cache from catalog
   resE <- liftIO $ runExceptT $ withSCUpdate cacheRef logger do
     rebuildableCache <- fst <$> liftIO (readIORef $ _scrCache cacheRef)
-    buildSchemaCacheWithOptions CatalogSync
+    ((), cache, _) <- buildSchemaCacheWithOptions CatalogSync invalidations
       & runCacheRWT rebuildableCache
       & peelRun runCtx pgCtx PG.ReadWrite
+    pure ((), cache)
   case resE of
     Left e   -> logError logger threadType $ TEQueryError e
     Right () -> logInfo logger threadType $ object ["message" .= msg]

server/src-rsr/initialise.sql

@@ -411,7 +411,8 @@ CREATE TABLE hdb_catalog.remote_schemas (
 
 CREATE TABLE hdb_catalog.hdb_schema_update_event (
   instance_id uuid NOT NULL,
-  occurred_at timestamptz NOT NULL DEFAULT NOW()
+  occurred_at timestamptz NOT NULL DEFAULT NOW(),
+  invalidations json NOT NULL
 );
 
 CREATE UNIQUE INDEX hdb_schema_update_event_one_row
@@ -422,13 +423,16 @@ $function$
   DECLARE
     instance_id uuid;
     occurred_at timestamptz;
+    invalidations json;
     curr_rec record;
   BEGIN
     instance_id = NEW.instance_id;
     occurred_at = NEW.occurred_at;
+    invalidations = NEW.invalidations;
     PERFORM pg_notify('hasura_schema_update', json_build_object(
       'instance_id', instance_id,
-      'occurred_at', occurred_at
+      'occurred_at', occurred_at,
+      'invalidations', invalidations
       )::text);
     RETURN curr_rec;
   END;
@@ -657,9 +661,9 @@ CREATE VIEW hdb_catalog.hdb_computed_field_function AS
   FROM hdb_catalog.hdb_computed_field
 );
 
-CREATE OR REPLACE FUNCTION hdb_catalog.check_violation(msg text) RETURNS bool AS 
+CREATE OR REPLACE FUNCTION hdb_catalog.check_violation(msg text) RETURNS bool AS
 $$
   BEGIN
     RAISE check_violation USING message=msg;
   END;
-$$ LANGUAGE plpgsql;
+$$ LANGUAGE plpgsql;

server/src-rsr/migrations/30_to_31.sql

@@ -0,0 +1,22 @@
+TRUNCATE hdb_catalog.hdb_schema_update_event;
+ALTER TABLE hdb_catalog.hdb_schema_update_event ADD COLUMN invalidations json NOT NULL;
+CREATE OR REPLACE FUNCTION hdb_catalog.hdb_schema_update_event_notifier() RETURNS trigger AS
+$function$
+  DECLARE
+    instance_id uuid;
+    occurred_at timestamptz;
+    invalidations json;
+    curr_rec record;
+  BEGIN
+    instance_id = NEW.instance_id;
+    occurred_at = NEW.occurred_at;
+    invalidations = NEW.invalidations;
+    PERFORM pg_notify('hasura_schema_update', json_build_object(
+      'instance_id', instance_id,
+      'occurred_at', occurred_at,
+      'invalidations', invalidations
+      )::text);
+    RETURN curr_rec;
+  END;
+$function$
+LANGUAGE plpgsql;

server/src-rsr/migrations/31_to_30.sql

@@ -0,0 +1,19 @@
+TRUNCATE hdb_catalog.hdb_schema_update_event;
+CREATE OR REPLACE FUNCTION hdb_catalog.hdb_schema_update_event_notifier() RETURNS trigger AS
+$function$
+  DECLARE
+    instance_id uuid;
+    occurred_at timestamptz;
+    curr_rec record;
+  BEGIN
+    instance_id = NEW.instance_id;
+    occurred_at = NEW.occurred_at;
+    PERFORM pg_notify('hasura_schema_update', json_build_object(
+      'instance_id', instance_id,
+      'occurred_at', occurred_at
+      )::text);
+    RETURN curr_rec;
+  END;
+$function$
+LANGUAGE plpgsql;
+ALTER TABLE hdb_catalog.hdb_schema_update_event DROP COLUMN invalidations;

server/src-test/Hasura/Server/MigrateSpec.hs

@@ -36,11 +36,10 @@ instance (MonadBase IO m) => TableCoreInfoRM (CacheRefT m)
 instance (MonadBase IO m) => CacheRM (CacheRefT m) where
   askSchemaCache = CacheRefT (fmap lastBuiltSchemaCache . readMVar)
 
-instance (MonadIO m, MonadBaseControl IO m, MonadTx m, MonadUnique m) => CacheRWM (CacheRefT m) where
+instance (MonadIO m, MonadBaseControl IO m, MonadTx m) => CacheRWM (CacheRefT m) where
-  buildSchemaCacheWithOptions options = CacheRefT $ flip modifyMVar \schemaCache ->
+  buildSchemaCacheWithOptions reason invalidations = CacheRefT $ flip modifyMVar \schemaCache -> do
-    swap <$> runCacheRWT schemaCache (buildSchemaCacheWithOptions options)
+    ((), cache, _) <- runCacheRWT schemaCache (buildSchemaCacheWithOptions reason invalidations)
-  invalidateCachedRemoteSchema name = CacheRefT $ flip modifyMVar \schemaCache ->
+    pure (cache, ())
-    swap <$> runCacheRWT schemaCache (invalidateCachedRemoteSchema name)
 
 instance Example (CacheRefT m ()) where
   type Arg (CacheRefT m ()) = CacheRefT m :~> IO

server/tests-py/queries/v1/set_table_is_enum/relationship_with_inconsistent_enum_table.yaml

@@ -0,0 +1,55 @@
+# This is a regression test for #3791.
+- description: Setup enum table, create relationship, and insert invalid enum value
+  url: /v1/query
+  status: 200
+  query:
+    type: bulk
+    args:
+    - type: set_table_is_enum
+      args:
+        table: weekdays
+        is_enum: true
+    - type: create_object_relationship
+      args:
+        table: employees
+        name: favorite_color_object
+        using:
+          foreign_key_constraint_on: favorite_color
+    - type: run_sql
+      args:
+        sql: INSERT INTO colors (value, comment) VALUES ('illegal+graphql+identifier', '')
+    - type: reload_metadata
+      args: {}
+
+- description: Query inconsistent objects
+  url: /v1/query
+  status: 200
+  response:
+    is_consistent: false
+    inconsistent_objects:
+    - definition:
+        schema: public
+        name: colors
+      reason: the table "colors" cannot be used as an enum because the value
+        "illegal+graphql+identifier" is not a valid GraphQL enum value name
+      type: table
+    - definition:
+        using:
+          foreign_key_constraint_on: favorite_color
+        name: favorite_color_object
+        comment:
+        table:
+          schema: public
+          name: employees
+      reason: table "colors" is not tracked
+      type: object_relation
+  query:
+    type: get_inconsistent_metadata
+    args: {}
+
+- description: Drop inconsistent objects
+  url: /v1/query
+  status: 200
+  query:
+    type: drop_inconsistent_metadata
+    args: {}

server/tests-py/test_schema_stitching.py

@@ -90,7 +90,7 @@ class TestRemoteSchemaBasic:
         q = mk_add_remote_q('simple 2', 'http://localhost:5000/hello-graphql')
         st_code, resp = hge_ctx.v1q(q)
         assert st_code == 400
-        assert resp['code'] == 'constraint-violation'
+        assert resp['code'] == 'unexpected'
 
     def test_remove_schema_error(self, hge_ctx):
         """remove remote schema which is not added"""

server/tests-py/test_v1_queries.py

@@ -679,6 +679,9 @@ class TestSetTableIsEnum(DefaultTestQueries):
     def test_add_test_schema_enum_table(self, hge_ctx):
         check_query_f(hge_ctx, self.dir() + '/add_test_schema_enum_table.yaml')
 
+    def test_relationship_with_inconsistent_enum_table(self, hge_ctx):
+        check_query_f(hge_ctx, self.dir() + '/relationship_with_inconsistent_enum_table.yaml')
+
 class TestSetTableCustomFields(DefaultTestQueries):
     @classmethod
     def dir(cls):
@@ -735,5 +738,3 @@ class TestBulkQuery(DefaultTestQueries):
 
     def test_run_bulk_with_select_and_reads(self, hge_ctx):
         check_query_f(hge_ctx, self.dir() + '/select_with_reads.yaml')
-
-