[gardening] remove Alias from Backend

### Description

In our haste to generalize everything for MSSQL, we put every single "suspicious" type in Backend, including ones that weren't required. `Alias` is one of those: it's only used in a type alias, and is actually just an implementation detail of the translation layer. This PR removes it.

https://github.com/hasura/graphql-engine-mono/pull/1759

GitOrigin-RevId: fb348934ec65a51aae7f95d93c83c3bb704587b5

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

@@ -21,7 +21,6 @@ instance Backend 'BigQuery where
   type SourceConfig            'BigQuery = BigQuery.BigQuerySourceConfig
   type SourceConnConfiguration 'BigQuery = BigQuery.BigQueryConnSourceConfig
   type Identifier              'BigQuery = Void
-  type Alias                   'BigQuery = BigQuery.EntityAlias
   type TableName               'BigQuery = BigQuery.TableName
   type FunctionName            'BigQuery = BigQuery.FunctionName
   type FunctionArgType         'BigQuery = Void

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

@@ -22,7 +22,6 @@ instance Backend 'MSSQL where
   type SourceConfig            'MSSQL = MSSQL.MSSQLSourceConfig
   type SourceConnConfiguration 'MSSQL = MSSQL.MSSQLConnConfiguration
   type Identifier              'MSSQL = Void
-  type Alias                   'MSSQL = MSSQL.EntityAlias
   type TableName               'MSSQL = MSSQL.TableName
   type FunctionName            'MSSQL = MSSQL.FunctionName
   type FunctionArgType         'MSSQL = Void

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

@@ -59,7 +59,6 @@ instance
   type SourceConfig            ('Postgres pgKind) = PG.PGSourceConfig
   type SourceConnConfiguration ('Postgres pgKind) = PG.PostgresConnConfiguration
   type Identifier              ('Postgres pgKind) = PG.Identifier
-  type Alias                   ('Postgres pgKind) = PG.Alias
   type TableName               ('Postgres pgKind) = PG.QualifiedTable
   type FunctionName            ('Postgres pgKind) = PG.QualifiedFunction
   type FunctionArgType         ('Postgres pgKind) = PG.QualifiedPGType

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

@@ -697,7 +697,9 @@ processOrderByItems sourcePrefix' fieldAlias' similarArrayFields orderByItems =
       cursor = mkCursorExp $ toList orderByItemExps
   pure (orderByExtractors, orderByExp, cursor)
   where
-    processAnnOrderByItem :: AnnOrderByItem ('Postgres pgKind) -> m (OrderByItemExp ('Postgres pgKind))
+    processAnnOrderByItem
+      :: AnnOrderByItem ('Postgres pgKind)
+      -> m (OrderByItemG ('Postgres pgKind) (AnnOrderByElement ('Postgres pgKind) (SQLExpression ('Postgres pgKind)), (S.Alias, SQLExpression ('Postgres pgKind))))
     processAnnOrderByItem orderByItem =
       forM orderByItem $ \ordByCol -> (ordByCol,) <$>
       processAnnOrderByElement sourcePrefix' fieldAlias' ordByCol
@@ -743,12 +745,16 @@ processOrderByItems sourcePrefix' fieldAlias' similarArrayFields orderByItems =
                , S.mkQIdenExp relSourcePrefix (mkAggregateOrderByAlias aggOrderBy)
                )
 
-    toOrderByExp :: OrderByItemExp ('Postgres pgKind) -> S.OrderByItem
+    toOrderByExp
+      :: OrderByItemG ('Postgres pgKind) (AnnOrderByElement ('Postgres pgKind) (SQLExpression ('Postgres pgKind)), (S.Alias, SQLExpression ('Postgres pgKind)))
+      -> S.OrderByItem
     toOrderByExp orderByItemExp =
       let OrderByItemG obTyM expAlias obNullsM = fst . snd <$> orderByItemExp
       in S.OrderByItem (S.SEIdentifier $ toIdentifier expAlias) obTyM obNullsM
 
-    mkCursorExp :: [OrderByItemExp ('Postgres pgKind)] -> S.SQLExp
+    mkCursorExp
+      :: [OrderByItemG ('Postgres pgKind) (AnnOrderByElement ('Postgres pgKind) (SQLExpression ('Postgres pgKind)), (S.Alias, SQLExpression ('Postgres pgKind)))]
+      -> S.SQLExp
     mkCursorExp orderByItemExps =
       S.applyJsonBuildObj $ flip concatMap orderByItemExps $
       \orderByItemExp ->

server/src-lib/Hasura/GraphQL/Execute/RemoteJoin/Join.hs

@@ -31,7 +31,7 @@ import           Hasura.GraphQL.Parser                   hiding (field)
 import           Hasura.GraphQL.RemoteServer             (execRemoteGQ)
 import           Hasura.GraphQL.Transport.HTTP.Protocol
 import           Hasura.RQL.IR.Select
-import           Hasura.RQL.Types                        hiding (Alias)
+import           Hasura.RQL.Types
 import           Hasura.Server.Version                   (HasVersion)
 import           Hasura.Session
 

server/src-lib/Hasura/RQL/IR/Select.hs

@@ -176,7 +176,6 @@ instance (Backend b) => Hashable (AnnAggregateOrderBy b)
 type AnnOrderByElement b v = AnnOrderByElementG b (AnnBoolExp b v)
 type AnnOrderByItemG b v = OrderByItemG b (AnnOrderByElement b v)
 type AnnOrderByItem b = AnnOrderByItemG b (SQLExpression b)
-type OrderByItemExp b = OrderByItemG b (AnnOrderByElement b (SQLExpression b), (Alias b, SQLExpression b))
 
 
 -- Fields

server/src-lib/Hasura/RQL/Types/Backend.hs

@@ -109,7 +109,6 @@ class
   type SourceConfig            b :: Type
   type SourceConnConfiguration b :: Type
   type Identifier              b :: Type
-  type Alias                   b :: Type
   type TableName               b :: Type
   type FunctionName            b :: Type
   type FunctionArgType         b :: Type