mssql: support query multiplexing in subscriptions

GitOrigin-RevId: 757ceba2c1cdb1107ce0b0e41d2e70ac795d0d73

CHANGELOG.md

@@ -14,6 +14,7 @@ only when there are enough present in the items inventory.
 
 ### Bug fixes and improvements
 
+- server: support query multiplexing in MSSQL subscriptions
 - console: add bigquery support (#1000)
 - cli: add support for bigquery in metadata operations
 

server/graphql-engine.cabal

@@ -356,9 +356,9 @@ library
 
                      , Hasura.Backends.MSSQL.Connection
                      , Hasura.Backends.MSSQL.DDL
+                     , Hasura.Backends.MSSQL.DDL.BoolExp
                      , Hasura.Backends.MSSQL.DDL.RunSQL
                      , Hasura.Backends.MSSQL.DDL.Source
-                     , Hasura.Backends.MSSQL.DDL.BoolExp
                      , Hasura.Backends.MSSQL.FromIr
                      , Hasura.Backends.MSSQL.Instances.Execute
                      , Hasura.Backends.MSSQL.Instances.Metadata
@@ -367,6 +367,7 @@ library
                      , Hasura.Backends.MSSQL.Instances.Types
                      , Hasura.Backends.MSSQL.Meta
                      , Hasura.Backends.MSSQL.Plan
+                     , Hasura.Backends.MSSQL.SQL.Value
                      , Hasura.Backends.MSSQL.ToQuery
                      , Hasura.Backends.MSSQL.Types
                      , Hasura.Backends.MSSQL.Types.Instances
@@ -571,6 +572,7 @@ library
                      , Hasura.SQL.GeoJSON
                      , Hasura.SQL.Time
                      , Hasura.SQL.Types
+                     , Hasura.SQL.Value
                      , Hasura.SQL.WKT
                      , Hasura.Tracing
                      , Network.HTTP.Client.Extended

server/src-lib/Hasura/Backends/MSSQL/Instances/Execute.hs

@@ -1,23 +1,27 @@
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
-module Hasura.Backends.MSSQL.Instances.Execute (NoMultiplex(..)) where
+module Hasura.Backends.MSSQL.Instances.Execute (MultiplexedQuery'(..), multiplexRootReselect) where
 
 import           Hasura.Prelude
 
+import qualified Data.Aeson.Extended                   as J
 import qualified Data.Environment                      as Env
-import qualified Data.HashMap.Strict.InsOrd            as OMap
+import qualified Data.List.NonEmpty                    as NE
+import qualified Data.Text.Extended                    as T
 import qualified Database.ODBC.SQLServer               as ODBC
 import qualified Language.GraphQL.Draft.Syntax         as G
 import qualified Network.HTTP.Client                   as HTTP
 import qualified Network.HTTP.Types                    as HTTP
 
-import           Data.Text.Extended
 
 import qualified Hasura.SQL.AnyBackend                 as AB
 
 import           Hasura.Backends.MSSQL.Connection
+import           Hasura.Backends.MSSQL.FromIr          as TSQL
 import           Hasura.Backends.MSSQL.Plan
+import           Hasura.Backends.MSSQL.SQL.Value       (toTxtEncodedVal)
 import           Hasura.Backends.MSSQL.ToQuery
+import           Hasura.Backends.MSSQL.Types           as TSQL
 import           Hasura.EncJSON
 import           Hasura.GraphQL.Context
 import           Hasura.GraphQL.Execute.Backend
@@ -29,7 +33,7 @@ import           Hasura.Session
 
 instance BackendExecute 'MSSQL where
   type PreparedQuery    'MSSQL = Text
-  type MultiplexedQuery 'MSSQL = NoMultiplex
+  type MultiplexedQuery 'MSSQL = MultiplexedQuery'
   type ExecutionMonad   'MSSQL = ExceptT QErr IO
   getRemoteJoins = const []
 
@@ -39,12 +43,12 @@ instance BackendExecute 'MSSQL where
   mkDBQueryExplain = msDBQueryExplain
   mkLiveQueryExplain = msDBLiveQueryExplain
 
+
 -- multiplexed query
+newtype MultiplexedQuery' = MultiplexedQuery' Reselect
 
-newtype NoMultiplex = NoMultiplex (G.Name, ODBC.Query)
-
-instance ToTxt NoMultiplex where
-  toTxt (NoMultiplex (_name, query)) = toTxt query
+instance T.ToTxt MultiplexedQuery' where
+  toTxt (MultiplexedQuery' reselect) = T.toTxt $ toQueryPretty $ fromReselect reselect
 
 
 -- query
@@ -73,9 +77,7 @@ msDBQueryPlan _env _manager _reqHeaders userInfo _directives sourceName sourceCo
     $ DBStepInfo sourceName sourceConfig (Just queryString) odbcQuery
 
 msDBQueryExplain
-  :: forall m
-    . ( MonadError QErr m
-      )
+  :: MonadError QErr m
   => G.Name
   -> UserInfo
   -> SourceName
@@ -95,18 +97,86 @@ msDBQueryExplain fieldName userInfo sourceName sourceConfig qrf = do
     $ DBStepInfo sourceName sourceConfig Nothing odbcQuery
 
 msDBLiveQueryExplain
-  :: ( MonadError QErr m
-     , MonadIO m
-     )
+  :: MonadError QErr m
   => LiveQueryPlan 'MSSQL (MultiplexedQuery 'MSSQL) -> m LiveQueryPlanExplanation
-msDBLiveQueryExplain (LiveQueryPlan plan sourceConfig variables) = do
-  let NoMultiplex (_name, query) = _plqpQuery plan
-      select    = withExplain $ QueryPrinter query
-      pool      = _mscConnectionPool sourceConfig
+msDBLiveQueryExplain (LiveQueryPlan plan _sourceConfig variables) = do
+  let query = _plqpQuery plan
       -- TODO: execute `select` in separate batch
       -- https://github.com/hasura/graphql-engine-mono/issues/1024
-  _explainInfo <- runJSONPathQuery pool (toQueryFlat select)
-  pure $ LiveQueryPlanExplanation (toTxt query) [] variables
+      -- select    = withExplain $ QueryPrinter query
+      -- pool      = _mscConnectionPool sourceConfig
+      -- explainInfo <- runJSONPathQuery pool (toQueryFlat select)
+  pure $ LiveQueryPlanExplanation (T.toTxt query) [] variables
+
+--------------------------------------------------------------------------------
+-- Producing the correct SQL-level list comprehension to multiplex a query
+
+-- Problem description:
+--
+-- Generate a query that repeats the same query N times but with
+-- certain slots replaced:
+--
+-- [ Select x y | (x,y) <- [..] ]
+--
+
+multiplexRootReselect
+  :: [(CohortId, CohortVariables)]
+  -> TSQL.Reselect
+  -> TSQL.Select
+multiplexRootReselect variables rootReselect =
+  Select
+    { selectTop = NoTop
+    , selectProjections =
+        [ FieldNameProjection
+            Aliased
+              { aliasedThing =
+                  TSQL.FieldName
+                    {fieldNameEntity = rowAlias, fieldName = resultIdAlias}
+              , aliasedAlias = resultIdAlias
+              }
+        , ExpressionProjection
+            Aliased
+              { aliasedThing =
+                  ColumnExpression
+                    (TSQL.FieldName
+                      { fieldNameEntity = resultAlias
+                      , fieldName = TSQL.jsonFieldName
+                      })
+              , aliasedAlias = resultAlias
+              }
+        ]
+    , selectFrom =
+        FromOpenJson
+          Aliased
+            { aliasedThing =
+                OpenJson
+                  { openJsonExpression =
+                      ValueExpression (ODBC.TextValue $ lbsToTxt $ J.encode variables)
+                  , openJsonWith =
+                      NE.fromList
+                        [ UuidField resultIdAlias (Just $ IndexPath RootPath 0)
+                        , JsonField resultVarsAlias (Just $ IndexPath RootPath 1)
+                        ]
+                  }
+            , aliasedAlias = rowAlias
+            }
+    , selectJoins =
+        [ Join
+            { joinSource = JoinReselect rootReselect
+            , joinJoinAlias =
+                JoinAlias
+                  { joinAliasEntity = resultAlias
+                  , joinAliasField = Just TSQL.jsonFieldName
+                  }
+            }
+        ]
+    , selectWhere = Where mempty
+    , selectFor =
+        JsonFor ForJson {jsonCardinality = JsonArray, jsonRoot = NoRoot}
+    , selectOrderBy = Nothing
+    , selectOffset = Nothing
+    }
+
 
 -- mutation
 
@@ -138,13 +208,18 @@ msDBSubscriptionPlan
   -> SourceConfig 'MSSQL
   -> InsOrdHashMap G.Name (QueryDB 'MSSQL (UnpreparedValue 'MSSQL))
   -> m (LiveQueryPlan 'MSSQL (MultiplexedQuery 'MSSQL))
-msDBSubscriptionPlan userInfo _sourceName sourceConfig rootFields = do
-  -- WARNING: only keeping the first root field for now!
-  query <- traverse mkQuery $ head $ OMap.toList rootFields
-  let roleName = _uiRole userInfo
-      parameterizedPlan = ParameterizedLiveQueryPlan roleName $ NoMultiplex query
+msDBSubscriptionPlan UserInfo {_uiSession, _uiRole} _sourceName sourceConfig rootFields = do
+  (reselect, prepareState) <- planMultiplex rootFields _uiSession
+  let PrepareState{sessionVariables, namedArguments, positionalArguments} = prepareState
+  -- TODO: call MSSQL validateVariables
+  -- We need to ensure that the values provided for variables are correct according to MSSQL.
+  -- Without this check an invalid value for a variable for one instance of the subscription will
+  -- take down the entire multiplexed query.
+  let cohortVariables = mkCohortVariables
+        sessionVariables
+        _uiSession
+        (toTxtEncodedVal namedArguments)
+        (toTxtEncodedVal positionalArguments)
+  let parameterizedPlan = ParameterizedLiveQueryPlan _uiRole $ MultiplexedQuery' reselect
   pure
-    $ LiveQueryPlan parameterizedPlan sourceConfig
-    $ mkCohortVariables mempty mempty mempty mempty
-  where
-    mkQuery = fmap (toQueryFlat . fromSelect) . planNoPlan userInfo
+    $ LiveQueryPlan parameterizedPlan sourceConfig cohortVariables

server/src-lib/Hasura/Backends/MSSQL/Instances/Transport.hs

@@ -6,16 +6,18 @@ import           Hasura.Prelude
 
 import qualified Data.Aeson                              as J
 import qualified Data.ByteString                         as B
+import qualified Database.ODBC.SQLServer                 as ODBC
 import qualified Language.GraphQL.Draft.Syntax           as G
 
+import           Data.String                             (fromString)
 import           Data.Text.Encoding                      (encodeUtf8)
 import           Data.Text.Extended
-import           Hasura.RQL.Types.Error                  as HE
 
 import qualified Hasura.Logging                          as L
 
 import           Hasura.Backends.MSSQL.Connection
 import           Hasura.Backends.MSSQL.Instances.Execute
+import           Hasura.Backends.MSSQL.ToQuery
 import           Hasura.EncJSON
 import           Hasura.GraphQL.Execute.Backend
 import           Hasura.GraphQL.Execute.LiveQuery.Plan
@@ -34,6 +36,14 @@ instance BackendTransport 'MSSQL  where
   runDBMutation = runMutation
   runDBSubscription = runSubscription
 
+newtype CohortResult = CohortResult (CohortId, Text)
+
+instance J.FromJSON CohortResult where
+  parseJSON = J.withObject "CohortResult" \o -> do
+    cohortId   <- o J..: "result_id"
+    cohortData <- o J..: "result"
+    pure $ CohortResult (cohortId, cohortData)
+
 runQuery
   :: ( MonadIO m
      , MonadQueryLog m
@@ -88,25 +98,29 @@ runMutation reqId query fieldName _userInfo logger _sourceConfig tx _genSql =  d
     $ run tx
 
 runSubscription
-  :: ( MonadIO m
-     )
+  :: MonadIO m
   => SourceConfig 'MSSQL
   -> MultiplexedQuery 'MSSQL
   -> [(CohortId, CohortVariables)]
   -> m (DiffTime, Either QErr [(CohortId, B.ByteString)])
-runSubscription sourceConfig (NoMultiplex (name, query)) variables = do
+runSubscription sourceConfig (MultiplexedQuery' reselect) variables = do
   let pool = _mscConnectionPool sourceConfig
-  withElapsedTime $ runExceptT $ for variables $ traverse $ const $
-    fmap toResult $ run $ runJSONPathQuery pool query
-  where
-    toResult :: Text -> B.ByteString
-    toResult = encodeUtf8 . addFieldName
-
-    -- TODO: This should probably be generated from the database or should
-    -- probably return encjson so that encJFromAssocList can be used
-    addFieldName result =
-      "{\"" <> G.unName name <> "\":" <> result <> "}"
+      multiplexed = multiplexRootReselect variables reselect
+      query = toQueryFlat $ fromSelect multiplexed
+  withElapsedTime $ runExceptT $ executeMultiplexedQuery pool query
 
+executeMultiplexedQuery
+  :: MonadIO m
+  => MSSQLPool
+  -> ODBC.Query
+  -> ExceptT QErr m [(CohortId, B.ByteString)]
+executeMultiplexedQuery pool query = do
+  let parseResult r = J.eitherDecodeStrict (encodeUtf8 r) `onLeft` \s -> throw400 ParseFailed (fromString s)
+      convertFromJSON :: [CohortResult] -> [(CohortId, B.ByteString)]
+      convertFromJSON = map \(CohortResult (cid, cresult)) -> (cid, encodeUtf8 cresult)
+  textResult   <- run $ runJSONPathQuery pool query
+  parsedResult <- parseResult textResult
+  pure $ convertFromJSON parsedResult
 
 run :: (MonadIO m, MonadError QErr m) => ExceptT QErr IO a -> m a
 run action = do

server/src-lib/Hasura/Backends/MSSQL/Plan.hs

@@ -13,7 +13,6 @@ import qualified Data.Aeson                    as J
 import qualified Data.HashMap.Strict           as HM
 import qualified Data.HashMap.Strict.InsOrd    as OMap
 import qualified Data.HashSet                  as Set
-import qualified Data.List.NonEmpty            as NE
 import qualified Data.Text                     as T
 import qualified Database.ODBC.SQLServer       as ODBC
 import qualified Language.GraphQL.Draft.Syntax as G
@@ -59,21 +58,22 @@ planNoPlan userInfo queryDB = do
             JsonFor forJson -> JsonFor forJson {jsonRoot = Root "root"}
       }
 
-  -- planMultiplex ::
-  --      OMap.InsOrdHashMap G.Name (SubscriptionRootFieldMSSQL (GraphQL.UnpreparedValue 'MSSQL))
-  --   -> Either PrepareError Select
-  -- planMultiplex _unpreparedMap =
-  -- let rootFieldMap =
-  --       evalState
-  --         (traverse
-  --            (traverseQueryRootField prepareValueMultiplex)
-  --            unpreparedMap)
-  --         emptyPrepareState
-  -- selectMap <-
-  --   first
-  --     FromIrError
-  --     (runValidate (TSQL.runFromIr (traverse TSQL.fromRootField rootFieldMap)))
-  -- pure (multiplexRootReselect (collapseMap selectMap))
+planMultiplex
+  :: MonadError QErr m
+  => OMap.InsOrdHashMap G.Name (QueryDB 'MSSQL (GraphQL.UnpreparedValue 'MSSQL))
+  -> SessionVariables
+  -> m (Reselect, PrepareState)
+planMultiplex unpreparedMap sessionVariables = do
+  let (rootFieldMap, prepareState) =
+        runState
+          (traverse
+            (traverseQueryDB (prepareValueMultiplex (getSessionVariablesSet sessionVariables)))
+            unpreparedMap)
+          emptyPrepareState
+  selectMap <-
+    runValidate (TSQL.runFromIr (traverse TSQL.fromRootField rootFieldMap))
+    `onLeft` (throw400 NotSupported . tshow)
+  pure (collapseMap selectMap, prepareState)
 
   -- Plan a query without prepare/exec.
   -- planNoPlanMap ::
@@ -119,10 +119,6 @@ globalSessionExpression :: TSQL.Expression
 globalSessionExpression =
   ValueExpression (ODBC.TextValue "current_setting('hasura.user')::json")
 
--- TODO: real env object.
-envObjectExpression :: TSQL.Expression
-envObjectExpression =
-  ValueExpression (ODBC.TextValue "[{\"result_id\":1,\"result_vars\":{\"synthetic\":[10]}}]")
 
 --------------------------------------------------------------------------------
 -- Resolving values
@@ -131,14 +127,17 @@ data PrepareError
   = FromIrError (NonEmpty TSQL.Error)
 
 data PrepareState = PrepareState
-  { positionalArguments :: !Integer
+  { positionalArguments :: ![RQL.ColumnValue 'MSSQL]
   , namedArguments      :: !(HashMap G.Name (RQL.ColumnValue 'MSSQL))
   , sessionVariables    :: !(Set.HashSet SessionVariable)
   }
 
 emptyPrepareState :: PrepareState
-emptyPrepareState =
-  PrepareState {positionalArguments = 0, namedArguments = mempty, sessionVariables = mempty}
+emptyPrepareState = PrepareState
+  { positionalArguments = mempty
+  , namedArguments = mempty
+  , sessionVariables = mempty
+  }
 
 -- | Prepare a value without any query planning; we just execute the
 -- query with the values embedded.
@@ -158,22 +157,37 @@ prepareValueNoPlan sessionVariables =
       pure $ ValueExpression $ ODBC.TextValue value
 
 -- | Prepare a value for multiplexed queries.
-prepareValueMultiplex ::
-     GraphQL.UnpreparedValue 'MSSQL
+prepareValueMultiplex
+  :: Set.HashSet SessionVariable
+  -> GraphQL.UnpreparedValue 'MSSQL
   -> State PrepareState TSQL.Expression
-prepareValueMultiplex =
+prepareValueMultiplex globalVariables =
   \case
     GraphQL.UVLiteral x -> pure x
-    GraphQL.UVSession ->
-      pure (JsonQueryExpression globalSessionExpression)
+    GraphQL.UVSession -> do
+      modify' (\s -> s {sessionVariables = sessionVariables s <> globalVariables})
+      pure $ JsonValueExpression
+        (ColumnExpression
+          FieldName
+          { fieldNameEntity = rowAlias
+          , fieldName = resultVarsAlias
+          })
+        (RootPath `FieldPath` "session")
     GraphQL.UVSessionVar _typ text -> do
       modify' (\s -> s {sessionVariables = text `Set.insert` sessionVariables s})
-      pure $ JsonValueExpression globalSessionExpression (FieldPath RootPath (toTxt text))
-    GraphQL.UVParameter mVariableInfo pgcolumnvalue ->
+      pure $ JsonValueExpression
+        (ColumnExpression
+          FieldName
+          { fieldNameEntity = rowAlias
+          , fieldName = resultVarsAlias
+          })
+        (RootPath `FieldPath` "session" `FieldPath` toTxt text)
+    GraphQL.UVParameter mVariableInfo columnValue ->
       case fmap GraphQL.getName mVariableInfo of
         Nothing -> do
-          index <- gets positionalArguments
-          modify' (\s -> s {positionalArguments = index + 1})
+          modify' (\s -> s {
+            positionalArguments = positionalArguments s <> [columnValue] })
+          index <- (toInteger . length) <$> gets positionalArguments
           pure
             (JsonValueExpression
                (ColumnExpression
@@ -187,76 +201,17 @@ prepareValueMultiplex =
             (\s ->
                s
                  { namedArguments =
-                     HM.insert name pgcolumnvalue (namedArguments s)
+                     HM.insert name columnValue (namedArguments s)
                  })
           pure
             (JsonValueExpression
-               envObjectExpression
+               (ColumnExpression
+                  FieldName
+                    { fieldNameEntity = rowAlias
+                    , fieldName = resultVarsAlias
+                    })
                (RootPath `FieldPath` "query" `FieldPath` G.unName name))
 
---------------------------------------------------------------------------------
--- Producing the correct SQL-level list comprehension to multiplex a query
-
--- Problem description:
---
--- Generate a query that repeats the same query N times but with
--- certain slots replaced:
---
--- [ Select x y | (x,y) <- [..] ]
---
-
-multiplexRootReselect :: TSQL.Reselect -> TSQL.Select
-multiplexRootReselect rootReselect =
-  Select
-    { selectTop = NoTop
-    , selectProjections =
-        [ FieldNameProjection
-            Aliased
-              { aliasedThing =
-                  FieldName
-                    {fieldNameEntity = rowAlias, fieldName = resultIdAlias}
-              , aliasedAlias = resultIdAlias
-              }
-        , ExpressionProjection
-            Aliased
-              { aliasedThing =
-                  JsonQueryExpression
-                    (ColumnExpression
-                       (FieldName
-                          { fieldNameEntity = resultAlias
-                          , fieldName = TSQL.jsonFieldName
-                          }))
-              , aliasedAlias = resultAlias
-              }
-        ]
-    , selectFrom =
-        FromOpenJson
-          Aliased
-            { aliasedThing =
-                OpenJson
-                  { openJsonExpression = envObjectExpression
-                  , openJsonWith =
-                      NE.fromList
-                        [IntField resultIdAlias, JsonField resultVarsAlias]
-                  }
-            , aliasedAlias = rowAlias
-            }
-    , selectJoins =
-        [ Join
-            { joinSource = JoinReselect rootReselect
-            , joinJoinAlias =
-                JoinAlias
-                  { joinAliasEntity = resultAlias
-                  , joinAliasField = Just TSQL.jsonFieldName
-                  }
-            }
-        ]
-    , selectWhere = Where mempty
-    , selectFor =
-        JsonFor ForJson {jsonCardinality = JsonArray, jsonRoot = NoRoot}
-    , selectOrderBy = Nothing
-    , selectOffset = Nothing
-    }
 
 resultIdAlias :: T.Text
 resultIdAlias = "result_id"

server/src-lib/Hasura/Backends/MSSQL/SQL/Value.hs

@@ -0,0 +1,19 @@
+module Hasura.Backends.MSSQL.SQL.Value where
+
+import           Hasura.Prelude
+
+import           Hasura.Backends.MSSQL.Types.Internal  (Value)
+import           Hasura.SQL.Value                      (TxtEncodedVal (..))
+
+import qualified Database.ODBC.SQLServer               as ODBC
+import qualified Hasura.GraphQL.Execute.LiveQuery.Plan as LQP
+import qualified Hasura.RQL.Types.Column               as RQL
+
+import           Hasura.SQL.Backend
+
+txtEncodedVal :: Value -> TxtEncodedVal
+txtEncodedVal ODBC.NullValue = TENull
+txtEncodedVal val            = TELit $ tshow val
+
+toTxtEncodedVal :: forall f. Functor f => f (RQL.ColumnValue 'MSSQL) -> LQP.ValidatedVariables f
+toTxtEncodedVal = LQP.ValidatedVariables . fmap (txtEncodedVal . RQL.cvValue)

server/src-lib/Hasura/Backends/MSSQL/ToQuery.hs

@@ -7,6 +7,7 @@ module Hasura.Backends.MSSQL.ToQuery
   ( fromSelect
   , withExplain
   , fromReselect
+  , toSQL
   , toQueryFlat
   , toQueryPretty
   , fromDelete
@@ -16,8 +17,6 @@ module Hasura.Backends.MSSQL.ToQuery
 import           Hasura.Prelude              hiding (GT, LT)
 
 import qualified Data.Text                   as T
-import qualified Data.Text.Lazy              as L
-import qualified Data.Text.Lazy.Builder      as L
 
 import           Data.List                   (intersperse)
 import           Data.String
@@ -64,7 +63,7 @@ fromExpression =
   \case
     JsonQueryExpression e -> "JSON_QUERY(" <+> fromExpression e <+> ")"
     JsonValueExpression e path ->
-      "JSON_VALUE(" <+> fromExpression e <+> fromPath path <+> ")"
+      "JSON_VALUE(" <+> fromExpression e <+> ", " <+> fromPath path <+> ")"
     ValueExpression value -> QueryPrinter (toSql value)
     AndExpression xs ->
       SepByPrinter
@@ -120,16 +119,10 @@ fromOp =
     NLIKE -> "NOT LIKE"
 
 fromPath :: JsonPath -> Printer
-fromPath path =
-  ", " <+> string path
-  where
-    string = fromExpression .
-             ValueExpression . TextValue . L.toStrict . L.toLazyText . go
-    go =
-      \case
+fromPath = \case
   RootPath      -> "$"
-        IndexPath r i -> go r <> "[" <> L.fromString (show i) <> "]"
-        FieldPath r f -> go r <> ".\"" <> L.fromText f <> "\""
+  IndexPath r i -> fromPath r <+> "[" <+> fromString (show i) <+> "]"
+  FieldPath r f -> fromPath r <+> ".\"" <+> fromString (T.unpack f) <+> "\""
 
 fromFieldName :: FieldName -> Printer
 fromFieldName (FieldName {..}) =
@@ -344,8 +337,12 @@ fromOpenJson OpenJson {openJsonExpression, openJsonWith} =
 fromJsonFieldSpec :: JsonFieldSpec -> Printer
 fromJsonFieldSpec =
   \case
-    IntField name  -> fromNameText name <+> " INT"
-    JsonField name -> fromNameText name <+> " NVARCHAR(MAX) AS JSON"
+    IntField name mPath    -> fromNameText name <+> " INT" <+> quote mPath
+    StringField name mPath -> fromNameText name <+> " NVARCHAR(MAX)" <+> quote mPath
+    UuidField name mPath   -> fromNameText name <+> " UNIQUEIDENTIFIER" <+> quote mPath
+    JsonField name mPath   -> fromJsonFieldSpec (StringField name mPath) <+> " AS JSON"
+    where
+      quote mPath = maybe "" ((\p -> " '" <+> p <+> "'"). fromPath) mPath
 
 fromTableName :: TableName -> Printer
 fromTableName TableName {tableName, tableSchema} =

server/src-lib/Hasura/Backends/MSSQL/Types/Internal.hs

@@ -203,8 +203,10 @@ data OpenJson = OpenJson
   }
 
 data JsonFieldSpec
-  = IntField Text
-  | JsonField Text
+  = IntField Text (Maybe JsonPath)
+  | JsonField Text (Maybe JsonPath)
+  | StringField Text (Maybe JsonPath)
+  | UuidField Text (Maybe JsonPath)
 
 data Aliased a = Aliased
   { aliasedThing :: !a

server/src-lib/Hasura/Backends/Postgres/Execute/LiveQuery.hs

@@ -68,7 +68,7 @@ validateVariables pgExecCtx variableValues = do
   let valSel = mkValidationSel $ toList variableValues
   Q.Discard () <- runQueryTx_ $ liftTx $
     Q.rawQE dataExnErrHandler (Q.fromBuilder $ toSQL valSel) [] False
-  pure . ValidatedVariables $ fmap (txtEncodedPGVal . cvValue) variableValues
+  pure . ValidatedVariables $ fmap (txtEncodedVal . cvValue) variableValues
   where
     mkExtr = flip S.Extractor Nothing . toTxtValue
     mkValidationSel vars =

server/src-lib/Hasura/Backends/Postgres/Execute/Mutation.hs

@@ -241,7 +241,7 @@ mutateAndFetchCols
   -> [ColumnInfo 'Postgres]
   -> (MutationCTE, DS.Seq Q.PrepArg)
   -> Bool
-  -> Q.TxE QErr (MutateResp TxtEncodedPGVal)
+  -> Q.TxE QErr (MutateResp TxtEncodedVal)
 mutateAndFetchCols qt cols (cte, p) strfyNum = do
   let mutationTx :: Q.FromRes a => Q.TxE QErr a
       mutationTx =

server/src-lib/Hasura/Backends/Postgres/SQL/Value.hs

@@ -6,8 +6,8 @@ module Hasura.Backends.Postgres.SQL.Value
   , scientificToInteger
   , scientificToFloat
 
-  , TxtEncodedPGVal(..)
-  , txtEncodedPGVal
+  , TxtEncodedVal(..)
+  , txtEncodedVal
 
   , binEncoder
   , txtEncoder
@@ -16,6 +16,8 @@ module Hasura.Backends.Postgres.SQL.Value
 
 import           Hasura.Prelude
 
+import           Hasura.SQL.Value                   (TxtEncodedVal (..))
+
 import qualified Data.Aeson.Text                    as AE
 import qualified Data.Aeson.Types                   as AT
 import qualified Data.ByteString                    as B
@@ -201,25 +203,8 @@ parsePGValue ty val = case (ty, val) of
       PGUnknown tyName ->
         fail $ "A string is expected for type: " ++ T.unpack tyName
 
-data TxtEncodedPGVal
-  = TENull
-  | TELit !Text
-  deriving (Show, Eq, Generic)
-
-instance Hashable TxtEncodedPGVal
-
-instance ToJSON TxtEncodedPGVal where
-  toJSON = \case
-    TENull  -> Null
-    TELit t -> String t
-
-instance FromJSON TxtEncodedPGVal where
-  parseJSON Null       = pure TENull
-  parseJSON (String t) = pure $ TELit t
-  parseJSON v          = AT.typeMismatch "String" v
-
-txtEncodedPGVal :: PGScalarValue -> TxtEncodedPGVal
-txtEncodedPGVal = \case
+txtEncodedVal :: PGScalarValue -> TxtEncodedVal
+txtEncodedVal = \case
   PGValInteger i  -> TELit $ tshow i
   PGValSmallInt i -> TELit $ tshow i
   PGValBigInt i   -> TELit $ tshow i
@@ -317,7 +302,7 @@ binEncoder = \case
   PGValUnknown t                   -> (PTI.auto, Just (TE.encodeUtf8 t, PQ.Text))
 
 txtEncoder :: PGScalarValue -> S.SQLExp
-txtEncoder colVal = case txtEncodedPGVal colVal of
+txtEncoder colVal = case txtEncodedVal colVal of
   TENull  -> S.SENull
   TELit t -> S.SELit t
 

server/src-lib/Hasura/Backends/Postgres/Translate/Mutation.hs

@@ -25,7 +25,7 @@ import           Hasura.SQL.Types
 -- `SELECT ("row"::table).* VALUES (1, 'Robert', 23) AS "row"`.
 mkSelectExpFromColumnValues
   :: (MonadError QErr m)
-  => QualifiedTable -> [ColumnInfo 'Postgres] -> [ColumnValues 'Postgres TxtEncodedPGVal] -> m S.Select
+  => QualifiedTable -> [ColumnInfo 'Postgres] -> [ColumnValues 'Postgres TxtEncodedVal] -> m S.Select
 mkSelectExpFromColumnValues qt allCols = \case
   []       -> return selNoRows
   colVals  -> do

server/src-lib/Hasura/GraphQL/Execute/Insert.hs

@@ -146,7 +146,7 @@ insertObject
   -> PGE.MutationRemoteJoinCtx
   -> Seq.Seq Q.PrepArg
   -> Bool
-  -> m (Int, Maybe (ColumnValues 'Postgres TxtEncodedPGVal))
+  -> m (Int, Maybe (ColumnValues 'Postgres TxtEncodedVal))
 insertObject env singleObjIns additionalColumns remoteJoinCtx planVars stringifyNum = Tracing.trace ("Insert " <> qualifiedObjectToText table) do
   validateInsert (map fst columns) (map IR._riRelInfo objectRels) (map fst additionalColumns)
 
@@ -197,7 +197,7 @@ insertObject env singleObjIns additionalColumns remoteJoinCtx planVars stringify
         _aiDefVals
 
     withArrRels
-      :: Maybe (ColumnValues 'Postgres TxtEncodedPGVal)
+      :: Maybe (ColumnValues 'Postgres TxtEncodedVal)
       -> m Int
     withArrRels colValM = do
       colVal <- onNothing colValM $ throw400 NotSupported cannotInsArrRelErr
@@ -207,8 +207,8 @@ insertObject env singleObjIns additionalColumns remoteJoinCtx planVars stringify
       return $ sum arrInsARows
 
     asSingleObject
-      :: [ColumnValues 'Postgres TxtEncodedPGVal]
-      -> m (Maybe (ColumnValues 'Postgres TxtEncodedPGVal))
+      :: [ColumnValues 'Postgres TxtEncodedVal]
+      -> m (Maybe (ColumnValues 'Postgres TxtEncodedVal))
     asSingleObject = \case
       []  -> pure Nothing
       [r] -> pure $ Just r
@@ -325,7 +325,7 @@ mkInsertQ table onConflictM insCols defVals (insCheck, updCheck) = do
 
 fetchFromColVals
   :: MonadError QErr m
-  => ColumnValues 'Postgres TxtEncodedPGVal
+  => ColumnValues 'Postgres TxtEncodedVal
   -> [ColumnInfo 'Postgres]
   -> m [(PGCol, PG.SQLExp)]
 fetchFromColVals colVal reqCols =

server/src-lib/Hasura/GraphQL/Execute/LiveQuery/Plan.hs

@@ -125,7 +125,7 @@ import           Hasura.Session
 -- Cohort
 
 newtype CohortId = CohortId { unCohortId :: UUID }
-  deriving (Show, Eq, Hashable, J.ToJSON, Q.FromCol)
+  deriving (Show, Eq, Hashable, J.ToJSON, J.FromJSON, Q.FromCol)
 
 newCohortId :: (MonadIO m) => m CohortId
 newCohortId = CohortId <$> liftIO UUID.nextRandom
@@ -233,14 +233,14 @@ instance Q.ToPrepArg CohortVariablesArray where
 --
 -- so if any variable values are invalid, the error will be caught early.
 
-newtype ValidatedVariables f = ValidatedVariables (f TxtEncodedPGVal)
+newtype ValidatedVariables f = ValidatedVariables (f TxtEncodedVal)
 
-deriving instance (Show      (f TxtEncodedPGVal)) => Show      (ValidatedVariables f)
-deriving instance (Eq        (f TxtEncodedPGVal)) => Eq        (ValidatedVariables f)
-deriving instance (Hashable  (f TxtEncodedPGVal)) => Hashable  (ValidatedVariables f)
-deriving instance (J.ToJSON  (f TxtEncodedPGVal)) => J.ToJSON  (ValidatedVariables f)
-deriving instance (Semigroup (f TxtEncodedPGVal)) => Semigroup (ValidatedVariables f)
-deriving instance (Monoid    (f TxtEncodedPGVal)) => Monoid    (ValidatedVariables f)
+deriving instance (Show (f TxtEncodedVal)) => Show (ValidatedVariables f)
+deriving instance (Eq (f TxtEncodedVal)) => Eq (ValidatedVariables f)
+deriving instance (Hashable (f TxtEncodedVal)) => Hashable (ValidatedVariables f)
+deriving instance (J.ToJSON (f TxtEncodedVal)) => J.ToJSON (ValidatedVariables f)
+deriving instance (Semigroup (f TxtEncodedVal)) => Semigroup (ValidatedVariables f)
+deriving instance (Monoid (f TxtEncodedVal)) => Monoid (ValidatedVariables f)
 
 type ValidatedQueryVariables     = ValidatedVariables (Map.HashMap G.Name)
 type ValidatedSyntheticVariables = ValidatedVariables []

server/src-lib/Hasura/SQL/Value.hs

@@ -0,0 +1,25 @@
+module Hasura.SQL.Value where
+
+import           Hasura.Prelude
+
+
+import qualified Data.Aeson       as A
+import qualified Data.Aeson.Types as AT
+import qualified Data.Text        as T
+
+data TxtEncodedVal
+  = TENull
+  | TELit !T.Text
+  deriving (Show, Eq, Generic)
+
+instance Hashable TxtEncodedVal
+
+instance A.ToJSON TxtEncodedVal where
+  toJSON = \case
+    TENull  -> AT.Null
+    TELit t -> AT.String t
+
+instance A.FromJSON TxtEncodedVal where
+  parseJSON A.Null       = pure TENull
+  parseJSON (A.String t) = pure $ TELit t
+  parseJSON v            = AT.typeMismatch "String" v

server/tests-py/queries/explain/schema_setup_mssql.yaml

@@ -0,0 +1,12 @@
+type: bulk
+args:
+
+- type: mssql_run_sql
+  args:
+    source: mssql
+    sql: |
+      CREATE TABLE [user](
+        id int identity NOT NULL PRIMARY KEY,
+        name TEXT NOT NULL,
+        age INTEGER
+      );

server/tests-py/queries/explain/schema_teardown_mssql.yaml

@@ -0,0 +1,8 @@
+type: bulk
+args:
+- type: mssql_run_sql
+  args:
+    source: mssql
+    cascade: true
+    sql: |
+      DROP TABLE [user];

server/tests-py/queries/explain/setup_mssql.yaml

@@ -0,0 +1,18 @@
+type: bulk
+args:
+
+- type: mssql_track_table
+  args:
+    source: mssql
+    table:
+      name: user
+- type: mssql_create_select_permission
+  args:
+    source: mssql
+    table:
+      name: user
+    role: user
+    permission:
+      columns: '*'
+      filter:
+        id: X-Hasura-User-Id

server/tests-py/queries/explain/teardown_mssql.yaml

@@ -0,0 +1,2 @@
+type: bulk
+args: []

server/tests-py/queries/subscriptions/multiplexing/schema_setup_mssql.yaml

@@ -0,0 +1,14 @@
+type: bulk
+args:
+  - type: mssql_run_sql
+    args:
+      source: mssql
+      sql: |
+        CREATE TABLE test(id int identity NOT NULL PRIMARY KEY);
+        create table articles(
+          id int identity NOT NULL PRIMARY KEY,
+          user_id int,
+          content text,
+          title text,
+          is_public bit default 0
+        );

server/tests-py/queries/subscriptions/multiplexing/schema_teardown_mssql.yaml

@@ -0,0 +1,8 @@
+type: bulk
+args:
+  - type: mssql_run_sql
+    args:
+      source: mssql
+      sql: |
+        DROP TABLE test;
+        DROP TABLE articles;

server/tests-py/queries/subscriptions/multiplexing/setup_mssql.yaml

@@ -0,0 +1,39 @@
+type: bulk
+args:
+  - type: mssql_track_table
+    args:
+      source: mssql
+      table:
+        name: test
+  - type: mssql_track_table
+    args:
+      source: mssql
+      table:
+        name: articles
+  - type: mssql_create_select_permission
+    args:
+      source: mssql
+      table:
+        name: articles
+      role: public
+      permission:
+        columns:
+          - title
+          - content
+        filter:
+          is_public: 1
+  - type: mssql_create_select_permission
+    args:
+      source: mssql
+      table:
+        name: articles
+      role: user
+      permission:
+        columns:
+          - user_id
+          - title
+          - content
+          - is_public
+        filter:
+          id:
+            _eq: X-Hasura-User-Id

server/tests-py/queries/subscriptions/multiplexing/teardown_mssql.yaml

@@ -0,0 +1,2 @@
+type: bulk
+args: []

server/tests-py/test_subscriptions.py

@@ -250,7 +250,8 @@ class TestSubscriptionLiveQueries:
         with pytest.raises(queue.Empty):
             ev = ws_client.get_ws_event(3)
 
-@usefixtures('per_method_tests_db_state')
+@pytest.mark.parametrize("backend", ['mssql', 'postgres'])
+@usefixtures('per_class_tests_db_state', 'per_backend_tests')
 class TestSubscriptionMultiplexing:
 
     @classmethod