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server: query remote server in a remote join query iff all arguments are not null (#31)
* server: query remote server in a remote join query iff all arguments are not null Co-authored-by: Karthikeyan Chinnakonda <karthikeyan@hasura.io> GITHUB_PR_NUMBER: 6199 GITHUB_PR_URL: https://github.com/hasura/graphql-engine/pull/6199 * Update server/src-lib/Hasura/Backends/Postgres/Execute/RemoteJoin.hs Co-authored-by: Brandon Simmons <brandon@hasura.io> * Apply suggestions from code review Co-authored-by: Brandon Simmons <brandon@hasura.io> * Update server/tests-py/test_remote_relationships.py Co-authored-by: Brandon Simmons <brandon@hasura.io> * Apply suggestions from code review Co-authored-by: Brandon Simmons <brandon@hasura.io> * use guard instead of case match * add comment about the remote relationship joining * add a comment about the design discussion * update CHANGELOG Co-authored-by: Karthikeyan Chinnakonda <karthikeyan@hasura.io> Co-authored-by: Brandon Simmons <brandon@hasura.io> GitOrigin-RevId: ce7e8288d37ad7c32705f96cb6363f6ad68f3c0a
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CHANGELOG.md
20
CHANGELOG.md
@ -123,6 +123,26 @@ const newTable: TableEntry = {
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### Breaking changes
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#### PDV
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This release contains the [PDV refactor (#4111)](https://github.com/hasura/graphql-engine/pull/4111), a significant rewrite of the internals of the server, which did include some breaking changes:
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- The semantics of explicit `null` values in `where` filters have changed according to the discussion in [issue 704](https://github.com/hasura/graphql-engine/issues/704#issuecomment-635571407): an explicit `null` value in a comparison input object will be treated as an error rather than resulting in the expression being evaluated to `True`. For instance: `delete_users(where: {id: {_eq: $userId}}) { name }` will yield an error if `$userId` is `null` instead of deleting all users.
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- The validation of required headers has been fixed (closing #14 and #3659):
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- if a query selects table `bar` through table `foo` via a relationship, the required permissions headers will be the union of the required headers of table `foo` and table `bar` (we used to only check the headers of the root table);
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- if an insert does not have an `on_conflict` clause, it will not require the update permissions headers.
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#### Remote Relationship
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In this release, a breaking change has been introduced:
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In a remote relationship query, the remote schema will be queried when all of the joining arguments
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are **not** `null` values. When there are `null` value(s), the remote schema won't be queried and the
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response of the remote relationship field will be `null`. Earlier, the remote schema
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was queried with the `null` value arguments and the response depended upon how the remote schema handled the `null`
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arguments.
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### Bug fixes and improvements
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@ -49,7 +49,6 @@ import Hasura.RQL.Types
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import Hasura.Server.Version (HasVersion)
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import Hasura.Session
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-- | Executes given query and fetch response JSON from Postgres. Substitutes remote relationship fields.
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executeQueryWithRemoteJoins
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:: ( HasVersion
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@ -89,7 +88,8 @@ processRemoteJoins env manager reqHdrs userInfo pgRes rjs = do
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jsonRes <- onLeft (AO.eitherDecode pgRes) (throw500 . T.pack)
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-- Step 2: Traverse through the JSON obtained in above step and generate composite JSON value with remote joins
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compositeJson <- traverseQueryResponseJSON rjMap jsonRes
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let remoteJoins = collectRemoteFields compositeJson
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-- The remote server is queried only when all of the joining fields are *not* NULL:
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let remoteJoins = catMaybes $ collectRemoteFields compositeJson
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-- Step 3: Make queries to remote server and fetch graphql response
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remoteServerResp <- fetchRemoteJoinFields env manager reqHdrs userInfo remoteJoins
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-- Step 4: Replace remote fields in composite json with remote join values
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@ -313,7 +313,7 @@ data RemoteJoinField
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-- from remote join map and query response JSON from Postgres.
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traverseQueryResponseJSON
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:: (MonadError QErr m)
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=> RemoteJoinMap 'Postgres -> AO.Value -> m (CompositeValue RemoteJoinField)
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=> RemoteJoinMap 'Postgres -> AO.Value -> m (CompositeValue (Maybe RemoteJoinField))
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traverseQueryResponseJSON rjm =
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flip runReaderT rjm . flip evalStateT (Counter 0) . traverseValue mempty
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where
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@ -322,24 +322,72 @@ traverseQueryResponseJSON rjm =
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askRemoteJoins path = asks (Map.lookup path)
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traverseValue :: (MonadError QErr m, MonadReader (RemoteJoinMap 'Postgres) m, MonadState Counter m)
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=> FieldPath -> AO.Value -> m (CompositeValue RemoteJoinField)
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=> FieldPath -> AO.Value -> m (CompositeValue (Maybe RemoteJoinField))
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traverseValue path = \case
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AO.Object obj -> traverseObject obj
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AO.Array arr -> CVObjectArray <$> mapM (traverseValue path) (toList arr)
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v -> pure $ CVOrdValue v
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where
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mkRemoteSchemaField siblingFields remoteJoin = do
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mkRemoteSchemaField
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:: (MonadError QErr m, MonadState Counter m)
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=> AO.Object
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-> RemoteJoin 'Postgres
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-> m (Maybe RemoteJoinField)
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mkRemoteSchemaField siblingFields remoteJoin = runMaybeT $ do
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counter <- getCounter
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let RemoteJoin fieldName inputArgs selSet hasuraFields fieldCall rsi _ = remoteJoin
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hasuraFieldVariables <- mapM (parseGraphQLName . getFieldNameTxt) $ toList hasuraFields
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siblingFieldArgsVars <- mapM (\(k,val) -> do
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(,) <$> parseGraphQLName k <*> ordJSONValueToGValue val)
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$ siblingFields
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-- when any of the joining fields are `NULL`, we don't query
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-- the remote schema
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--
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-- The rationale for performing such a join is that, postgres
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-- implements joins in the same way. For example:
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-- Let's say we have the following tables
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--
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-- test_db=# select * from users;
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-- id | first_name | last_name
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-- ----+------------+-----------
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-- 4 | foo |
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-- 5 | baz | bar
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-- 6 | hello |
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-- (3 rows)
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-- test_db=# select * from address;
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-- id | first_name | last_name | address
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-- ----+------------+-----------+----------
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-- 4 | foo | | address1
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-- 5 | baz | bar | address2
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-- 6 | | hello | address3
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--
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-- Executing the following query:
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-- select u.first_name,u.last_name,a.address
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-- from users u
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-- left join address a on u.first_name = a.first_name
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-- and u.last_name = a.last_name;
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--
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-- gives the following result:
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--
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-- first_name | last_name | address
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-- -----------+-----------+----------
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-- baz | bar | address2
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-- foo | |
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-- hello | |
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--
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-- The data from the `address` table is fetched only when all
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-- of the arguments are **NOT** NULL.
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--
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-- For discussion of this design here
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-- see: https://github.com/hasura/graphql-engine-mono/pull/31#issuecomment-728230307
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for_ hasuraFields $ \(FieldName fieldNameTxt) -> do
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fldValue <- hoistMaybe $ AO.lookup fieldNameTxt siblingFields
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guard $ fldValue /= AO.Null
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hasuraFieldVariables <- lift $ mapM (parseGraphQLName . getFieldNameTxt) $ toList hasuraFields
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siblingFieldArgsVars <- lift $ mapM (\(k,val) -> do
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(,) <$> parseGraphQLName k <*> ordJSONValueToGValue val)
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$ AO.toList siblingFields
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let siblingFieldArgs = Map.fromList $ siblingFieldArgsVars
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hasuraFieldArgs = flip Map.filterWithKey siblingFieldArgs $ \k _ -> k `elem` hasuraFieldVariables
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fieldAlias <- pathToAlias (appendPath fieldName path) counter
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queryField <- fieldCallsToField (inputArgsToMap inputArgs) hasuraFieldArgs selSet fieldAlias fieldCall
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fieldAlias <- lift $ pathToAlias (appendPath fieldName path) counter
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queryField <- lift $ fieldCallsToField (inputArgsToMap inputArgs) hasuraFieldArgs selSet fieldAlias fieldCall
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pure $ RemoteJoinField rsi
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fieldAlias
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queryField
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@ -364,9 +412,9 @@ traverseQueryResponseJSON rjm =
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phantomColumnFields = map (fromPGCol . pgiColumn) $
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concatMap _rjPhantomFields remoteJoins
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if | fieldName `elem` phantomColumnFields -> pure Nothing
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| otherwise ->
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| otherwise -> do
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case find ((== fieldName) . _rjName) remoteJoins of
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Just rj -> Just . CVFromRemote <$> mkRemoteSchemaField fields rj
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Just rj -> Just . CVFromRemote <$> mkRemoteSchemaField obj rj
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Nothing -> Just <$> traverseValue fieldPath value
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pure $ CVObject $ OMap.fromList processedFields
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@ -499,16 +547,18 @@ fetchRemoteJoinFields env manager reqHdrs userInfo remoteJoins = do
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-- | Replace 'RemoteJoinField' in composite JSON with it's json value from remote server response.
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replaceRemoteFields
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:: MonadError QErr m
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=> CompositeValue RemoteJoinField
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=> CompositeValue (Maybe RemoteJoinField)
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-> AO.Object
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-> m AO.Value
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replaceRemoteFields compositeJson remoteServerResponse =
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compositeValueToJSON <$> traverse replaceValue compositeJson
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where
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replaceValue rj = do
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let alias = _rjfAlias rj
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fieldCall = _rjfFieldCall rj
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extractAtPath (alias:fieldCall) $ AO.Object remoteServerResponse
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-- `Nothing` below signifies that at-least one of the joining fields was NULL
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-- , when that happens we have to manually insert the `NULL` value for the
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-- remoteField value in the response.
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replaceValue Nothing = pure $ AO.Null
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replaceValue (Just RemoteJoinField {_rjfAlias, _rjfFieldCall}) =
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extractAtPath (_rjfAlias:_rjfFieldCall) $ AO.Object remoteServerResponse
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-- | 'FieldCall' is path to remote relationship value in remote server response.
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-- 'extractAtPath' traverse through the path and extracts the json value
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@ -606,9 +656,8 @@ substituteVariables values = traverse go
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where
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go = \case
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G.VVariable variableName ->
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case Map.lookup variableName values of
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Nothing -> Failure ["Value for variable " <> variableName <<> " not provided"]
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Just value -> pure value
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onNothing (Map.lookup variableName values) $
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Failure ["Value for variable " <> variableName <<> " not provided"]
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G.VList listValue ->
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fmap G.VList (traverse go listValue)
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G.VObject objectValue ->
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@ -15,6 +15,7 @@ module Hasura.Prelude
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, base64Decode
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, spanMaybeM
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, liftEitherM
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, hoistMaybe
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-- * Efficient coercions
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, coerce
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, findWithIndex
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@ -179,3 +180,7 @@ startTimer = do
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return $ do
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aft <- liftIO Clock.getMonotonicTimeNSec
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return $ nanoseconds $ fromIntegral (aft - bef)
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-- copied from http://hackage.haskell.org/package/errors-2.3.0/docs/src/Control.Error.Util.html#hoistMaybe
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hoistMaybe :: (Monad m) => Maybe b -> MaybeT m b
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hoistMaybe = MaybeT . return
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@ -0,0 +1,33 @@
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description: Remote join with null joining fields
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url: /v1/graphql
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status: 200
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response:
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data:
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employees:
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- id: 1
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name: alice
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employeeMessages:
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- id: 1
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name: alice
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msg: You win!
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- id: 2
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name: null
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# since the join argument (name) was `NULL`, we don't perform the remote query
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# and just return `null` for the joined field:
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employeeMessages: null
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- id: 3
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name: bob
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employeeMessages: []
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query:
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query: |
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query {
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employees {
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id
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name
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employeeMessages {
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id
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name
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msg
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}
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}
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}
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@ -52,3 +52,17 @@ args:
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args:
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schema: public
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name: authors
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- type: run_sql
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args:
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sql: |
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create table employees (
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id serial primary key,
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name text
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);
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insert into employees (name) values ('alice'),(NULL),('bob');
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- type: track_table
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args:
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schema: public
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name: employees
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@ -0,0 +1,16 @@
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type: create_remote_relationship
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args:
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name: employeeMessages
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table: employees
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hasura_fields:
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- id
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- name
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remote_schema: my-remote-schema
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remote_field:
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messages:
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arguments:
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where:
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name:
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eq: "$name"
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includes:
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id: ["$id"]
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@ -15,6 +15,11 @@ args:
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sql: |
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drop table if exists authors
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- type: run_sql
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args:
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sql: |
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drop table if exists employees
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# also drops remote relationship as direct dep
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- type: remove_remote_schema
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args:
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@ -186,6 +186,12 @@ class TestExecution:
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assert st_code == 200, resp
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check_query_f(hge_ctx, self.dir() + 'basic_multiple_fields.yaml')
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# https://github.com/hasura/graphql-engine/issues/5448
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def test_remote_join_fields_with_null_joining_fields(self, hge_ctx):
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st_code, resp = hge_ctx.v1q_f(self.dir() + 'setup_remote_rel_null_joining_fields.yaml')
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assert st_code == 200, resp
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check_query_f(hge_ctx, self.dir() + 'remote_rel_with_null_joining_fields.yaml')
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def test_nested_fields(self, hge_ctx):
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st_code, resp = hge_ctx.v1q_f(self.dir() + 'setup_remote_rel_nested_fields.yaml')
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assert st_code == 200, resp
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