server/mssql: fix aggregations

Aggregate fields - both the table and the relationship fields haven't been enabled till now. This PR fixes enables the aggregate fields and fixes an issue with root aggregate fields.

Co-authored-by: Chris Done <11019+chrisdone@users.noreply.github.com>
GitOrigin-RevId: a6d7ed9b45cda6af659a57576a8623c725a7372f

CHANGELOG.md

@@ -6,7 +6,7 @@
 ### Bug fixes and improvements
 
 (Add entries below in the order of: server, console, cli, docs, others)
-
+- server: aggregation fields are now supported on mssql
 - server: accept a new server config flag `--events-fetch-batch-size` to configure the number of rows being fetched from the events log table in a single batch
 - server: fix regression: `on_conflict` was missing in the schema for inserts in tables where the current user has no columns listed in their update permissions (fix #6804)
 - server: fix one-to-one relationship bug (introduced in #459) which prevented adding one-to-one relationships which didn't have the same column name for target and source

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

@@ -46,6 +46,7 @@ import           Hasura.SQL.Backend
 data Error
   = UnsupportedOpExpG (IR.OpExpG 'MSSQL Expression)
   | FunctionNotSupported
+  | NodesUnsupportedForNow
   deriving (Show, Eq)
 
 -- | The base monad used throughout this module for all conversion
@@ -188,7 +189,7 @@ fromSelectAggregate annSelectG = do
       , selectJoins = argsJoins <> mapMaybe fieldSourceJoin fieldSources
       , selectWhere = argsWhere <> Where [filterExpression]
       , selectFor =
-          JsonFor ForJson {jsonCardinality = JsonSingleton, jsonRoot = NoRoot}
+          JsonFor ForJson {jsonCardinality = JsonSingleton, jsonRoot = Root "aggregate"}
       , selectOrderBy = argsOrderBy
       , selectOffset = argsOffset
       }
@@ -502,7 +503,8 @@ fromTableAggregateFieldG (IR.FieldName name, field) =
              { aliasedThing = TSQL.ValueExpression (ODBC.TextValue text)
              , aliasedAlias = name
              })
-    IR.TAFNodes x _ -> case x of {}
+    IR.TAFNodes {} ->
+      refute (pure NodesUnsupportedForNow)
 
 fromAggregateField :: IR.AggregateField 'MSSQL -> ReaderT EntityAlias FromIr Aggregate
 fromAggregateField aggregateField =

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

@@ -44,7 +44,7 @@ instance BackendSchema 'MSSQL where
   buildFunctionMutationFields    = msBuildFunctionMutationFields
   -- backend extensions
   relayExtension    = const Nothing
-  nodesAggExtension = const Nothing
+  nodesAggExtension = const $ Just ()
   -- indivdual components
   columnParser              = msColumnParser
   jsonPathArg               = msJsonPathArg

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

@@ -41,7 +41,7 @@ instance Backend 'MSSQL where
   type XComputedField          'MSSQL = XDisable
   type XRemoteField            'MSSQL = XDisable
   type XRelay                  'MSSQL = XDisable
-  type XNodesAgg               'MSSQL = XDisable
+  type XNodesAgg               'MSSQL = XEnable
   type XDistinct               'MSSQL = XDisable
 
   functionArgScalarType :: FunctionArgType 'MSSQL -> ScalarType 'MSSQL

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

@@ -55,7 +55,17 @@ planNoPlan userInfo queryDB = do
       { selectFor =
           case selectFor select of
             NoFor           -> NoFor
-            JsonFor forJson -> JsonFor forJson {jsonRoot = Root "root"}
+            JsonFor forJson ->
+              JsonFor forJson {jsonRoot =
+                                 case jsonRoot forJson of
+                                   NoRoot -> Root "root"
+                                   -- Keep whatever's there if already
+                                   -- specified. In the case of an
+                                   -- aggregate query, the root will
+                                   -- be specified "aggregate", for
+                                   -- example.
+                                   keep   -> keep
+                              }
       }
 
 planMultiplex

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

@@ -138,9 +138,7 @@ fromDelete Delete {deleteTable, deleteWhere} =
     ]
 
 fromSelect :: Select -> Printer
-fromSelect Select {..} = case selectFor of
-  NoFor     -> result
-  JsonFor _ -> SeqPrinter ["SELECT ISNULL((", result, "), '[]')"]
+fromSelect Select {..} = wrapFor selectFor result
   where
     result =
       SepByPrinter
@@ -186,18 +184,20 @@ fromJoinSource =
     JoinReselect reselect -> fromReselect reselect
 
 fromReselect :: Reselect -> Printer
-fromReselect Reselect {..} =
-  SepByPrinter
-    NewlinePrinter
-    [ "SELECT " <+>
-      IndentPrinter
-        7
-        (SepByPrinter
-           ("," <+> NewlinePrinter)
-           (map fromProjection (toList reselectProjections)))
-    , fromFor reselectFor
-    , fromWhere reselectWhere
-    ]
+fromReselect Reselect {..} = wrapFor reselectFor result
+  where
+    result =
+      SepByPrinter
+        NewlinePrinter
+        [ "SELECT " <+>
+          IndentPrinter
+            7
+            (SepByPrinter
+               ("," <+> NewlinePrinter)
+               (map fromProjection (toList reselectProjections)))
+        , fromFor reselectFor
+        , fromWhere reselectWhere
+        ]
 
 fromOrderBys ::
      Top -> Maybe Expression -> Maybe (NonEmpty OrderBy) -> Printer
@@ -258,15 +258,11 @@ fromFor :: For -> Printer
 fromFor =
   \case
     NoFor -> ""
-    JsonFor ForJson {jsonCardinality, jsonRoot = root} ->
+    JsonFor ForJson {jsonCardinality} ->
       "FOR JSON PATH" <+>
       case jsonCardinality of
-        JsonArray -> ""
-        JsonSingleton ->
-          ", WITHOUT_ARRAY_WRAPPER" <+>
-          case root of
-            NoRoot    -> ""
-            Root text -> "ROOT(" <+> QueryPrinter (toSql text) <+> ")"
+        JsonArray     -> ""
+        JsonSingleton -> ", WITHOUT_ARRAY_WRAPPER"
 
 fromProjection :: Projection -> Printer
 fromProjection =
@@ -362,6 +358,32 @@ trueExpression = ValueExpression (BoolValue True)
 falseExpression :: Expression
 falseExpression = ValueExpression (BoolValue False)
 
+-- | Wrap a select with things needed when using FOR JSON.
+wrapFor :: For -> Printer -> Printer
+wrapFor for' inner = nullToArray
+  where
+    nullToArray =
+      case for' of
+        NoFor     -> rooted
+        JsonFor _ -> SeqPrinter ["SELECT ISNULL((", rooted, "), '[]')"]
+    rooted =
+      case for' of
+        JsonFor ForJson {jsonRoot, jsonCardinality = JsonSingleton} ->
+          case jsonRoot of
+            NoRoot -> inner
+            -- This is gross, but unfortunately ROOT and
+            -- WITHOUT_ARRAY_WRAPPER are not allowed to be used at the
+            -- same time (reason not specified). Therefore we just
+            -- concatenate the necessary JSON string literals around
+            -- the JSON.
+            Root text ->
+              SeqPrinter
+                [ fromString ("SELECT CONCAT('{" <> show text <> ":', (")
+                , inner
+                , "), '}')"
+                ]
+        _ -> inner
+
 --------------------------------------------------------------------------------
 -- Basic printing API