graphql-engine/server/src-lib/Hasura/GraphQL/Execute/Query.hs
Antoine Leblanc 6e1761f8f9 Enable remote joins from remote schemas in the execution engine.
### Description

This PR adds the ability to perform remote joins from remote schemas in the engine. To do so, we alter the definition of an `ExecutionStep` targeting a remote schema: the `ExecStepRemote` constructor now expects a `Maybe RemoteJoins`. This new argument is used when processing the execution step, in the transport layer (either `Transport.HTTP` or `Transport.WebSocket`).

For this `Maybe RemoteJoins` to be extracted from a parsed query, this PR also extends the `Execute.RemoteJoin.Collect` module, to implement "collection" from a selection set. Not only do those new functions extract the remote joins, but they also apply all necessary transformations to the selection sets (such as inserting the necessary "phantom" fields used as join keys).

Finally in `Execute.RemoteJoin.Join`, we make two changes. First, we now always look for nested remote joins, regardless of whether the join we just performed went to a source or a remote schema; and second we adapt our join tree logic according to the special cases that were added to deal with remote server edge cases.

Additionally, this PR refactors / cleans / documents `Execute.RemoteJoin.RemoteServer`. This is not required as part of this change and could be moved to a separate PR if needed (a similar cleanup of `Join` is done independently in #3894). It also introduces a draft of a new documentation page for this project, that will be refined in the release PR that ships the feature (either #3069 or a copy of it).

While this PR extends the engine, it doesn't plug such relationships in the schema, meaning that, as of this PR, the new code paths in `Join` are technically unreachable. Adding the corresponding schema code and, ultimately, enabling the metadata API will be done in subsequent PRs.

### Keeping track of concrete type names

The main change this PR makes to the existing `Join` code is to handle a new reserved field we sometimes use when targeting remote servers: the `__hasura_internal_typename` field. In short, a GraphQL selection set can sometimes "branch" based on the concrete "runtime type" of the object on which the selection happens:

```graphql
query {
  author(id: 53478) {
    ... on Writer {
      name
      articles {
        title
      }
    }
    ... on Artist {
      name
      articles {
        title
      }
    }
  }
}
```

If both of those `articles` are remote joins, we need to be able, when we get the answer, to differentiate between the two different cases. We do this by asking for `__typename`, to be able to decide if we're in the `Writer` or the `Artist` branch of the query.

To avoid further processing / customization of results, we only insert this `__hasura_internal_typename: __typename` field in the query in the case of unions of interfaces AND if we have the guarantee that we will processing the request as part of the remote joins "folding": that is, if there's any remote join in this branch in the tree. Otherwise, we don't insert the field, and we leave that part of the response untouched.

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/3810
GitOrigin-RevId: 89aaf16274d68e26ad3730b80c2d2fdc2896b96c
2022-03-09 03:18:22 +00:00

127 lines
5.2 KiB
Haskell

module Hasura.GraphQL.Execute.Query
( convertQuerySelSet,
parseGraphQLQuery,
)
where
import Data.Aeson qualified as J
import Data.Environment qualified as Env
import Data.HashMap.Strict qualified as Map
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.Tagged qualified as Tagged
import Hasura.Base.Error
import Hasura.GraphQL.Context
import Hasura.GraphQL.Execute.Action
import Hasura.GraphQL.Execute.Backend
import Hasura.GraphQL.Execute.Common
import Hasura.GraphQL.Execute.Instances ()
import Hasura.GraphQL.Execute.Remote
import Hasura.GraphQL.Execute.RemoteJoin.Collect qualified as RJ
import Hasura.GraphQL.Execute.Resolve
import Hasura.GraphQL.Namespace
import Hasura.GraphQL.ParameterizedQueryHash
import Hasura.GraphQL.Parser
import Hasura.GraphQL.Parser.Directives
import Hasura.GraphQL.Transport.HTTP.Protocol qualified as GH
import Hasura.Logging qualified as L
import Hasura.Prelude
import Hasura.QueryTags
import Hasura.RQL.IR
import Hasura.RQL.Types
import Hasura.SQL.AnyBackend qualified as AB
import Hasura.Server.Types (RequestId (..))
import Hasura.Session
import Language.GraphQL.Draft.Syntax qualified as G
import Network.HTTP.Client qualified as HTTP
import Network.HTTP.Types qualified as HTTP
parseGraphQLQuery ::
MonadError QErr m =>
GQLContext ->
[G.VariableDefinition] ->
Maybe (HashMap G.Name J.Value) ->
[G.Directive G.Name] ->
G.SelectionSet G.NoFragments G.Name ->
m
( RootFieldMap (QueryRootField UnpreparedValue),
[G.Directive Variable],
G.SelectionSet G.NoFragments Variable
)
parseGraphQLQuery gqlContext varDefs varValsM directives fields = do
(resolvedDirectives, resolvedSelSet) <- resolveVariables varDefs (fromMaybe Map.empty varValsM) directives fields
parsedQuery <- (gqlQueryParser gqlContext >>> (`onLeft` reportParseErrors)) resolvedSelSet
pure (parsedQuery, resolvedDirectives, resolvedSelSet)
convertQuerySelSet ::
forall m.
( MonadError QErr m,
MonadGQLExecutionCheck m,
MonadQueryTags m
) =>
Env.Environment ->
L.Logger L.Hasura ->
GQLContext ->
UserInfo ->
HTTP.Manager ->
HTTP.RequestHeaders ->
[G.Directive G.Name] ->
G.SelectionSet G.NoFragments G.Name ->
[G.VariableDefinition] ->
GH.GQLReqUnparsed ->
SetGraphqlIntrospectionOptions ->
RequestId ->
-- | Graphql Operation Name
Maybe G.Name ->
m (ExecutionPlan, [QueryRootField UnpreparedValue], DirectiveMap, ParameterizedQueryHash)
convertQuerySelSet
env
logger
gqlContext
userInfo
manager
reqHeaders
directives
fields
varDefs
gqlUnparsed
introspectionDisabledRoles
reqId
maybeOperationName = do
-- Parse the GraphQL query into the RQL AST
(unpreparedQueries, normalizedDirectives, normalizedSelectionSet) <-
parseGraphQLQuery gqlContext varDefs (GH._grVariables gqlUnparsed) directives fields
-- Transform the query plans into an execution plan
let usrVars = _uiSession userInfo
-- Process directives on the query
dirMap <-
(`onLeft` reportParseErrors)
=<< runParseT (parseDirectives customDirectives (G.DLExecutable G.EDLQUERY) normalizedDirectives)
let parameterizedQueryHash = calculateParameterizedQueryHash normalizedSelectionSet
executionPlan <- flip OMap.traverseWithKey unpreparedQueries $ \rootFieldName rootFieldUnpreparedValue -> do
case rootFieldUnpreparedValue of
RFDB sourceName exists ->
AB.dispatchAnyBackend @BackendExecute
exists
\(SourceConfigWith (sourceConfig :: (SourceConfig b)) queryTagsConfig (QDBR db)) -> do
let queryTagsAttributes = encodeQueryTags $ QTQuery $ QueryMetadata reqId maybeOperationName rootFieldName parameterizedQueryHash
queryTagsComment = Tagged.untag $ createQueryTags @m queryTagsAttributes queryTagsConfig
(noRelsDBAST, remoteJoins) = RJ.getRemoteJoins db
dbStepInfo <- flip runReaderT queryTagsComment $ mkDBQueryPlan @b userInfo sourceName sourceConfig noRelsDBAST
pure $ ExecStepDB [] (AB.mkAnyBackend dbStepInfo) remoteJoins
RFRemote rf -> do
RemoteSchemaRootField remoteSchemaInfo resultCustomizer remoteField <- runVariableCache $ for rf $ resolveRemoteVariable userInfo
let (noRelsRemoteField, remoteJoins) = RJ.getRemoteJoinsGraphQLField remoteField
pure $ buildExecStepRemote remoteSchemaInfo resultCustomizer G.OperationTypeQuery noRelsRemoteField remoteJoins (GH._grOperationName gqlUnparsed)
RFAction action -> do
let (noRelsDBAST, remoteJoins) = RJ.getRemoteJoinsActionQuery action
(actionExecution, actionName, fch) <- pure $ case noRelsDBAST of
AQQuery s -> (AEPSync $ resolveActionExecution env logger userInfo s (ActionExecContext manager reqHeaders usrVars) (Just (GH._grQuery gqlUnparsed)), _aaeName s, _aaeForwardClientHeaders s)
AQAsync s -> (AEPAsyncQuery $ AsyncActionQueryExecutionPlan (_aaaqActionId s) $ resolveAsyncActionQuery userInfo s, _aaaqName s, _aaaqForwardClientHeaders s)
pure $ ExecStepAction actionExecution (ActionsInfo actionName fch) remoteJoins
RFRaw r -> flip onLeft throwError =<< executeIntrospection userInfo r introspectionDisabledRoles
pure (executionPlan, OMap.elems unpreparedQueries, dirMap, parameterizedQueryHash)