Support query explain for MSSQL (fixes #1024)

Co-authored-by: Abby Sassel <3883855+sassela@users.noreply.github.com>
Co-authored-by: Vamshi Surabhi <6562944+0x777@users.noreply.github.com>
GitOrigin-RevId: 5a57d7570884a5469a947742e4ab9290a0cff55f

CHANGELOG.md

@@ -8,12 +8,13 @@
 
 - server: fix query execution of custom function containing a composite argument type
 - server: fix a bug in query validation that would cause some queries using default variable values to be rejected (fix #6867)
+- server: REST endpoint bugfix for UUID url params
 - server: custom URI schemes are now supported in CORS config (fix #5818) (#5940)
+- server: explaining/analyzing a query now works for mssql sources
 - server: fix MSSQL multiplexed subscriptions (fix #6887)
 - console: read-only modify page for mssql
 - console: filter out partitions from track table list and display partition info
 - console: fixes an issue where no schemas are listed on an MSSQL source
-- server: REST endpoint bugfix for UUID url params
 
 ## v2.0.0-alpha.10
 

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

@@ -76,6 +76,16 @@ msDBQueryPlan _env _manager _reqHeaders userInfo _directives sourceName sourceCo
     . AB.mkAnyBackend
     $ DBStepInfo @'MSSQL sourceName sourceConfig (Just queryString) odbcQuery
 
+runShowplan
+  :: ODBC.Query -> ODBC.Connection -> IO [Text]
+runShowplan query conn = do
+  ODBC.exec conn "SET SHOWPLAN_TEXT ON"
+  texts <- ODBC.query conn query
+  ODBC.exec conn "SET SHOWPLAN_TEXT OFF"
+  -- we don't need to use 'finally' here - if an exception occurs,
+  -- the connection is removed from the resource pool in 'withResource'.
+  pure texts
+
 msDBQueryExplain
   :: MonadError QErr m
   => G.Name
@@ -85,28 +95,33 @@ msDBQueryExplain
   -> QueryDB 'MSSQL (UnpreparedValue 'MSSQL)
   -> m (AB.AnyBackend DBStepInfo)
 msDBQueryExplain fieldName userInfo sourceName sourceConfig qrf = do
-  select <- withExplain . fromSelect <$> planNoPlan userInfo qrf
-  let queryString = ODBC.renderQuery $ toQueryPretty select
+  select <- fromSelect <$> planNoPlan userInfo qrf
+  let query = toQueryPretty select
+      queryString = ODBC.renderQuery $ query
       pool        = _mscConnectionPool sourceConfig
-      -- TODO: execute `select` in separate batch
-      -- https://github.com/hasura/graphql-engine-mono/issues/1024
-      odbcQuery   = runJSONPathQuery pool (toQueryFlat select) <&> \explainInfo ->
-        encJFromJValue $ ExplainPlan fieldName (Just queryString) (Just [explainInfo])
+      odbcQuery   =
+        withMSSQLPool
+          pool
+          (\conn -> do
+            showplan <- runShowplan query conn
+            pure (encJFromJValue $
+                  ExplainPlan
+                    fieldName
+                    (Just queryString)
+                    (Just showplan)))
   pure
     $ AB.mkAnyBackend
     $ DBStepInfo @'MSSQL 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 query = _plqpQuery plan
-      -- TODO: execute `select` in separate batch
-      -- https://github.com/hasura/graphql-engine-mono/issues/1024
-      -- select    = withExplain $ QueryPrinter query
-      -- pool      = _mscConnectionPool sourceConfig
-      -- explainInfo <- runJSONPathQuery pool (toQueryFlat select)
-  pure $ LiveQueryPlanExplanation (T.toTxt query) [] variables
+msDBLiveQueryExplain (LiveQueryPlan plan sourceConfig variables) = do
+  let (MultiplexedQuery' reselect) = _plqpQuery plan
+      query = toQueryPretty $ fromSelect $ multiplexRootReselect [(dummyCohortId, variables)] reselect
+      pool = _mscConnectionPool sourceConfig
+  explainInfo <- withMSSQLPool pool (runShowplan query)
+  pure $ LiveQueryPlanExplanation (T.toTxt query) explainInfo variables
 
 --------------------------------------------------------------------------------
 -- Producing the correct SQL-level list comprehension to multiplex a query

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

@@ -5,7 +5,6 @@
 
 module Hasura.Backends.MSSQL.ToQuery
   ( fromSelect
-  , withExplain
   , fromReselect
   , toSQL
   , toQueryFlat
@@ -178,15 +177,6 @@ fromSelect Select {..} = wrapFor selectFor result
       , fromFor selectFor
       ]
 
-withExplain :: Printer -> Printer
-withExplain p =
-  SepByPrinter
-    NewlinePrinter
-      [ "SET SHOWPLAN_TEXT ON"
-      , p
-      , "SET SHOWPLAN_TEXT OFF"
-      ]
-
 fromJoinSource :: JoinSource -> Printer
 fromJoinSource =
   \case

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

@@ -89,6 +89,7 @@ Additional details are provided by the documentation for individual bindings.
 -}
 module Hasura.GraphQL.Execute.LiveQuery.Plan
   ( CohortId
+  , dummyCohortId
   , newCohortId
   , CohortIdArray(..)
   , CohortVariablesArray(..)
@@ -108,6 +109,7 @@ import qualified Data.Aeson.Extended                as J
 import qualified Data.Aeson.TH                      as J
 import qualified Data.HashMap.Strict                as Map
 import qualified Data.HashSet                       as Set
+import qualified Data.UUID                          as UUID
 import qualified Data.UUID.V4                       as UUID
 import qualified Database.PG.Query                  as Q
 import qualified Database.PG.Query.PTI              as PTI
@@ -130,6 +132,9 @@ newtype CohortId = CohortId { unCohortId :: UUID }
 newCohortId :: (MonadIO m) => m CohortId
 newCohortId = CohortId <$> liftIO UUID.nextRandom
 
+dummyCohortId :: CohortId
+dummyCohortId = CohortId UUID.nil
+
 data CohortVariables
   = CohortVariables
   { _cvSessionVariables   :: !SessionVariables

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

@@ -0,0 +1,32 @@
+description: Explain query with permissions
+url: /v1/graphql/explain
+status: 200
+response:
+  - field: user
+    plan:
+      - "SELECT ISNULL((SELECT [t_user1].[id] AS [id],\n       [t_user1].[name] AS [name],\n\
+        \       [t_user1].[age] AS [age]\nFROM [dbo].[user] AS [t_user1]\nWHERE ((((([t_user1].[id])\
+        \ = ((N'1')))\n       OR ((([t_user1].[id]) IS NULL)\n      AND (((N'1')) IS NULL)))))\n\
+        FOR JSON PATH), '[]')"
+      - "  |--Compute Scalar(DEFINE:([Expr1003]=isnull([Expr1001],CONVERT_IMPLICIT(nvarchar(max),'[]',0))))"
+      - "       |--UDX(([t_user1].[id], [t_user1].[name], [t_user1].[age]))"
+      - "            |--Clustered Index Seek(OBJECT:([master].[dbo].[user].[PK__user__3213E83F2F718733]
+        AS [t_user1]), SEEK:([t_user1].[id]=(1)) ORDERED FORWARD)"
+    sql:
+      "SELECT ISNULL((SELECT [t_user1].[id] AS [id],\n       [t_user1].[name] AS\
+      \ [name],\n       [t_user1].[age] AS [age]\nFROM [dbo].[user] AS [t_user1]\nWHERE\
+      \ ((((([t_user1].[id]) = ((N'1')))\n       OR ((([t_user1].[id]) IS NULL)\n  \
+      \    AND (((N'1')) IS NULL)))))\nFOR JSON PATH), '[]')"
+query:
+  user:
+    X-Hasura-Role: user
+    X-Hasura-User-Id: "1"
+  query:
+    query: |
+      query {
+        user{
+          id
+          name
+          age
+        }
+      }

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

@@ -0,0 +1,27 @@
+description: Explain query
+url: /v1/graphql/explain
+status: 200
+response:
+  - field: user
+    plan:
+      - "SELECT ISNULL((SELECT [t_user1].[id] AS [id],\n       [t_user1].[name] AS [name],\n\
+        \       [t_user1].[age] AS [age]\nFROM [dbo].[user] AS [t_user1]\nFOR JSON PATH),\
+        \ '[]')"
+      - "  |--Compute Scalar(DEFINE:([Expr1003]=isnull([Expr1001],CONVERT_IMPLICIT(nvarchar(max),'[]',0))))"
+      - "       |--UDX(([t_user1].[id], [t_user1].[name], [t_user1].[age]))"
+      - "            |--Clustered Index Scan(OBJECT:([master].[dbo].[user].[PK__user__3213E83F2F718733]
+        AS [t_user1]))"
+    sql:
+      "SELECT ISNULL((SELECT [t_user1].[id] AS [id],\n       [t_user1].[name] AS\
+      \ [name],\n       [t_user1].[age] AS [age]\nFROM [dbo].[user] AS [t_user1]\nFOR\
+      \ JSON PATH), '[]')"
+query:
+  query:
+    query: |
+      query {
+        user{
+          id
+          name
+          age
+        }
+      }

server/tests-py/test_graphql_queries.py

@@ -875,17 +875,18 @@ class TestUnauthorizedRolePermission:
     def test_unauth_role(self, hge_ctx, transport):
         check_query_f(hge_ctx, self.dir() + '/unauthorized_role.yaml', transport, False)
 
-@usefixtures('per_class_tests_db_state')
+@pytest.mark.parametrize("backend", ['postgres', 'mssql'])
+@usefixtures('per_class_tests_db_state', 'per_backend_tests')
 class TestGraphQLExplain:
     @classmethod
     def dir(cls):
         return 'queries/explain'
 
-    def test_simple_query(self, hge_ctx):
-        self.with_admin_secret(hge_ctx, self.dir() + '/simple_query.yaml')
+    def test_simple_query(self, hge_ctx, backend):
+        self.with_admin_secret(hge_ctx, self.dir() + hge_ctx.backend_suffix('/simple_query') + ".yaml")
 
-    def test_permissions_query(self, hge_ctx):
-        self.with_admin_secret(hge_ctx, self.dir() + '/permissions_query.yaml')
+    def test_permissions_query(self, hge_ctx, backend):
+        self.with_admin_secret(hge_ctx, self.dir() + hge_ctx.backend_suffix('/permissions_query') + ".yaml")
 
     def with_admin_secret(self, hge_ctx, f):
         conf = get_conf_f(f)
@@ -895,8 +896,7 @@ class TestGraphQLExplain:
             headers['X-Hasura-Admin-Secret'] = hge_ctx.hge_key
         status_code, resp_json, _ = hge_ctx.anyq(conf['url'], conf['query'], headers)
         assert status_code == 200, resp_json
-        # Comparing only with generated 'sql' since the 'plan' is not consistent
-        # across all Postgres versions
+        # Comparing only with generated 'sql' since the 'plan' may differ
         resp_sql = resp_json[0]['sql']
         exp_sql = conf['response'][0]['sql']
         assert resp_sql == exp_sql, resp_json