mssql isolation level option

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/9626
GitOrigin-RevId: 43861a982afadd9fdefb7d8996999e051e751222

docs/docs/api-reference/syntax-defs.mdx

@@ -127,10 +127,11 @@ keywords:
 
 ## MsSQLSourceConnectionInfo {#mssqlsourceconnectioninfo}
 
-| Key               | Required | Schema                                  | Description                                                   |
-| ----------------- | -------- | --------------------------------------- | ------------------------------------------------------------- |
-| connection_string | true     | `String` \| [FromEnv](#fromenv)         | The database connection string, or as an environment variable |
-| pool_settings     | false    | [MsSQLPoolSettings](#mssqlpoolsettings) | Connection pool settings                                      |
+| Key               | Required | Schema                                                                                     | Description                                                                                                           |
+| ----------------- | -------- | ------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------- |
+| connection_string | true     | `String` \| [FromEnv](#fromenv)                                                            | The database connection string, or as an environment variable                                                         |
+| pool_settings     | false    | [MsSQLPoolSettings](#mssqlpoolsettings)                                                    | Connection pool settings                                                                                              |
+| isolation_level   | false    | `read-uncommited` \| `read-committed` \| `repeatable-read` \| `snapshot` \| `serializable` | The transaction isolation level in which the queries made to the source will be run with (default: `read-committed`). |
 
 ## FromEnv {#fromenv}
 

metadata.openapi.json

@@ -4935,6 +4935,11 @@
                             }
                         ]
                     },
+                    "isolation_level": {
+                        "default": "read-committed",
+                        "description": "The transaction isolation level in which the queries made to the source will be run with (default: read-committed).\nIsolation level",
+                        "type": "string"
+                    },
                     "pool_settings": {
                         "$ref": "#/components/schemas/MSSQLPoolSettings"
                     }

server/src-lib/Database/MSSQL/Transaction.hs

@@ -18,9 +18,13 @@ module Database.MSSQL.Transaction
   )
 where
 
+import Autodocodec (HasCodec (codec), bimapCodec, textCodec, (<?>))
+import Autodocodec.Aeson qualified as AC
 import Control.Exception (try)
 import Control.Monad.Morph (MFunctor (hoist))
 import Control.Monad.Trans.Control (MonadBaseControl)
+import Data.Aeson qualified as J
+import Data.Text qualified as T
 import Database.MSSQL.Pool
 import Database.ODBC.SQLServer (FromRow)
 import Database.ODBC.SQLServer qualified as ODBC
@@ -243,17 +247,62 @@ data TransactionState
     -- rollback of the transaction.
     TSUncommittable
 
+-- | <https://learn.microsoft.com/en-us/sql/t-sql/statements/set-transaction-isolation-level-transact-sql>
 data TxIsolation
-  = ReadCommitted
+  = ReadUncommitted
+  | ReadCommitted
   | RepeatableRead
+  | Snapshot
   | Serializable
+  deriving (Eq, Generic)
 
 instance Show TxIsolation where
   show = \case
+    ReadUncommitted -> "READ UNCOMMITTED"
     ReadCommitted -> "READ COMMITTED"
     RepeatableRead -> "REPEATABLE READ"
+    Snapshot -> "SNAPSHOT"
     Serializable -> "SERIALIZABLE"
 
+instance Hashable TxIsolation
+
+instance NFData TxIsolation
+
+instance HasCodec TxIsolation where
+  codec =
+    bimapCodec
+      decode
+      encode
+      textCodec
+      <?> "Isolation level"
+    where
+      decode :: Text -> Either String TxIsolation
+      decode = \case
+        "read-uncommitted" -> Right ReadUncommitted
+        "read-committed" -> Right ReadCommitted
+        "repeatable-read" -> Right RepeatableRead
+        "snapshot" -> Right Snapshot
+        "serializable" -> Right Serializable
+        _ ->
+          Left
+            $ T.unpack
+            $ "Unexpected options for isolation_level. Expected "
+            <> "'read-uncommited' | 'read-committed' | 'repeatable-read' | 'snapshot' | 'serializable'"
+      encode :: TxIsolation -> Text
+      encode = \case
+        ReadUncommitted -> "read-uncommitted"
+        ReadCommitted -> "read-committed"
+        RepeatableRead -> "repeatable-read"
+        Snapshot -> "snapshot"
+        Serializable -> "serializable"
+
+instance J.ToJSON TxIsolation where
+  toJSON = AC.toJSONViaCodec
+  toEncoding = AC.toEncodingViaCodec
+
+instance J.FromJSON TxIsolation where
+  parseJSON = AC.parseJSONViaCodec
+
 -- | Wraps an action in a transaction. Rolls back on errors.
 asTransaction ::
   forall e a m.

server/src-lib/Hasura/App.hs

@@ -1466,7 +1466,7 @@ mkPgSourceResolver pgLogger env _ config = runExceptT do
 
 mkMSSQLSourceResolver :: SourceResolver ('MSSQL)
 mkMSSQLSourceResolver env _name (MSSQLConnConfiguration connInfo _) = runExceptT do
-  let MSSQLConnectionInfo iConnString MSSQLPoolSettings {..} = connInfo
+  let MSSQLConnectionInfo iConnString MSSQLPoolSettings {..} isolationLevel = connInfo
       connOptions =
         MSPool.ConnectionOptions
           { _coConnections = fromMaybe defaultMSSQLMaxConnections _mpsMaxConnections,
@@ -1474,6 +1474,6 @@ mkMSSQLSourceResolver env _name (MSSQLConnConfiguration connInfo _) = runExceptT
             _coIdleTime = _mpsIdleTimeout
           }
   (connString, mssqlPool) <- createMSSQLPool iConnString connOptions env
-  let mssqlExecCtx = mkMSSQLExecCtx mssqlPool NeverResizePool
+  let mssqlExecCtx = mkMSSQLExecCtx isolationLevel mssqlPool NeverResizePool
       numReadReplicas = 0
   pure $ MSSQLSourceConfig connString mssqlExecCtx numReadReplicas

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

@@ -35,6 +35,7 @@ import Data.Aeson qualified as J
 import Data.Environment qualified as Env
 import Data.Has
 import Data.Text (pack, unpack)
+import Data.Text qualified as T
 import Data.Time (localTimeToUTC)
 import Database.MSSQL.Pool qualified as MSPool
 import Database.MSSQL.Transaction qualified as MSTx
@@ -148,7 +149,8 @@ defaultMSSQLPoolSettings =
 
 data MSSQLConnectionInfo = MSSQLConnectionInfo
   { _mciConnectionString :: InputConnectionString,
-    _mciPoolSettings :: MSSQLPoolSettings
+    _mciPoolSettings :: MSSQLPoolSettings,
+    _mciIsolationLevel :: MSTx.TxIsolation
   }
   deriving (Show, Eq, Generic)
 
@@ -164,6 +166,14 @@ instance HasCodec MSSQLConnectionInfo where
       AC..= _mciConnectionString
         <*> requiredField' "pool_settings"
       AC..= _mciPoolSettings
+        <*> AC.optionalFieldWithDefault "isolation_level" MSTx.ReadCommitted isolationLevelDoc
+      AC..= _mciIsolationLevel
+    where
+      isolationLevelDoc =
+        T.unwords
+          [ "The transaction isolation level in which the queries made to the",
+            "source will be run with (default: read-committed)."
+          ]
 
 instance ToJSON MSSQLConnectionInfo where
   toJSON = genericToJSON hasuraJSON
@@ -176,6 +186,9 @@ instance FromJSON MSSQLConnectionInfo where
       <*> o
       .:? "pool_settings"
       .!= defaultMSSQLPoolSettings
+      <*> o
+      .:? "isolation_level"
+      .!= MSTx.ReadCommitted
 
 data MSSQLConnConfiguration = MSSQLConnConfiguration
   { _mccConnectionInfo :: MSSQLConnectionInfo,
@@ -251,11 +264,11 @@ data MSSQLExecCtx = MSSQLExecCtx
   }
 
 -- | Creates a MSSQL execution context for a single primary pool
-mkMSSQLExecCtx :: MSPool.MSSQLPool -> ResizePoolStrategy -> MSSQLExecCtx
-mkMSSQLExecCtx pool resizeStrategy =
+mkMSSQLExecCtx :: MSTx.TxIsolation -> MSPool.MSSQLPool -> ResizePoolStrategy -> MSSQLExecCtx
+mkMSSQLExecCtx isolationLevel pool resizeStrategy =
   MSSQLExecCtx
-    { mssqlRunReadOnly = \tx -> MSTx.runTxE defaultMSSQLTxErrorHandler MSTx.ReadCommitted tx pool,
-      mssqlRunReadWrite = \tx -> MSTx.runTxE defaultMSSQLTxErrorHandler MSTx.ReadCommitted tx pool,
+    { mssqlRunReadOnly = \tx -> MSTx.runTxE defaultMSSQLTxErrorHandler isolationLevel tx pool,
+      mssqlRunReadWrite = \tx -> MSTx.runTxE defaultMSSQLTxErrorHandler isolationLevel tx pool,
       mssqlRunSerializableTx = \tx -> MSTx.runTxE defaultMSSQLTxErrorHandler MSTx.Serializable tx pool,
       mssqlDestroyConn = MSPool.drainMSSQLPool pool,
       mssqlResizePools =