[server] revert #2078 "server/postgres: optimize SQL query generation…

… with LIMITs"

Fixes #7453, by reverting #2078 (commit 47eaccd).

https://hasurahq.slack.com/archives/CKFUG6RCH/p1629900718181700

hasura/graphql-engine-mono#2204

GitOrigin-RevId: 53d5fee

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

@@ -25,74 +25,20 @@ data SourcePrefixes
   } deriving (Show, Eq, Generic)
 instance Hashable SourcePrefixes
 
--- | Select portion of rows generated by the query using limit and offset
-data SelectSlicing
-  = SelectSlicing
-  { _ssLimit  :: !(Maybe Int)
-  , _ssOffset :: !(Maybe Int64)
-  } deriving (Show, Eq, Generic)
-instance Hashable SelectSlicing
-
--- | Sorting with -- Note [Optimizing queries using limit/offset])
-data SelectSorting
-  = NoSorting !(Maybe PG.DistinctExpr)
-  | SortAtBase !PG.OrderByExp !(Maybe PG.DistinctExpr)
-  -- ^ Apply sorting at base table selection. Sorting only via table columns
-  | SortAtNode !PG.OrderByExp !(Maybe PG.DistinctExpr)
-  -- ^ Apply sorting at outer selection. Sorting involves atleast one non-column order by item
-  deriving (Show, Eq, Generic)
-instance Hashable SelectSorting
-
-data SortingAndSlicing
-  = SortingAndSlicing
-  { _sasSorting :: !SelectSorting
-  , _sasSlicing :: !SelectSlicing
-  } deriving (Show, Eq, Generic)
-instance Hashable SortingAndSlicing
-
 data SelectSource
   = SelectSource
-  { _ssPrefix            :: !PG.Identifier
-  , _ssFrom              :: !PG.FromItem
-  , _ssWhere             :: !PG.BoolExp
-  , _ssSortingAndSlicing :: !SortingAndSlicing
+  { _ssPrefix   :: !PG.Identifier
+  , _ssFrom     :: !PG.FromItem
+  , _ssDistinct :: !(Maybe PG.DistinctExpr)
+  , _ssWhere    :: !PG.BoolExp
+  , _ssOrderBy  :: !(Maybe PG.OrderByExp)
+  , _ssLimit    :: !(Maybe Int)
+  , _ssOffset   :: !(Maybe Int64)
   } deriving (Generic)
 instance Hashable SelectSource
 deriving instance Show SelectSource
 deriving instance Eq   SelectSource
 
-noSortingAndSlicing :: SortingAndSlicing
-noSortingAndSlicing =
-  SortingAndSlicing (NoSorting Nothing) noSlicing
-
-noSlicing :: SelectSlicing
-noSlicing = SelectSlicing Nothing Nothing
-
-orderByForJsonAgg :: SelectSource -> Maybe PG.OrderByExp
-orderByForJsonAgg SelectSource{..} =
-  case (_sasSorting _ssSortingAndSlicing) of
-    NoSorting{}          -> Nothing
-    SortAtBase{}         -> Nothing
-    SortAtNode orderBy _ -> Just orderBy
-
-data ApplySortingAndSlicing
-  = ApplySortingAndSlicing
-  { _applyAtBase :: !(Maybe PG.OrderByExp, SelectSlicing, Maybe PG.DistinctExpr)
-  , _applyAtNode :: !(Maybe PG.OrderByExp, SelectSlicing, Maybe PG.DistinctExpr)
-  }
-
-applySortingAndSlicing :: SortingAndSlicing -> ApplySortingAndSlicing
-applySortingAndSlicing SortingAndSlicing{..} =
-  case _sasSorting of
-    NoSorting distinctExp             -> applyAtBase Nothing distinctExp
-    SortAtBase orderByExp distinctExp -> applyAtBase (Just orderByExp) distinctExp
-    SortAtNode orderByExp distinctExp -> applyAtNode orderByExp distinctExp
-  where
-    applyAtBase orderByExp distinctExp =
-      ApplySortingAndSlicing (orderByExp, _sasSlicing, distinctExp) (Nothing, noSlicing, Nothing)
-    applyAtNode orderByExp distinctExp =
-      ApplySortingAndSlicing (Nothing, noSlicing, Nothing) (Just orderByExp, _sasSlicing, distinctExp)
-
 data SelectNode
   = SelectNode
   { _snExtractors :: !(HM.HashMap PG.Alias PG.SQLExp)
@@ -113,7 +59,7 @@ instance Hashable ObjectSelectSource
 
 objectSelectSourceToSelectSource :: ObjectSelectSource -> SelectSource
 objectSelectSourceToSelectSource ObjectSelectSource{..} =
-  SelectSource _ossPrefix _ossFrom _ossWhere noSortingAndSlicing
+  SelectSource _ossPrefix _ossFrom Nothing _ossWhere Nothing Nothing Nothing
 
 data ObjectRelationSource
   = ObjectRelationSource

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

@@ -526,6 +526,5 @@ insertFunctionArg argName idx value (FunctionArgsExp positional named) =
 -- Lenses
 
 $(makeLenses ''AnnSelectG)
-$(makeLenses ''SelectArgsG)
 $(makePrisms ''AnnFieldG)
 $(makePrisms ''AnnotatedOrderByElement)

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

@@ -9,16 +9,6 @@ args:
         name TEXT NOT NULL,
         age INTEGER
       );
-      CREATE TABLE author(
-        id SERIAL PRIMARY KEY,
-        name TEXT NOT NULL
-      );
-      CREATE TABLE article(
-        id SERIAL PRIMARY KEY,
-        title TEXT NOT NULL,
-        content TEXT,
-        author_id INTEGER REFERENCES author(id)
-      );
 
 - type: track_table
   args:
@@ -32,20 +22,3 @@ args:
       columns: '*'
       filter:
         id: X-Hasura-User-Id
-
-- type: track_table
-  args:
-    name: author
-    schema: public
-
-- type: track_table
-  args:
-    name: article
-    schema: public
-
-- type: create_object_relationship
-  args:
-    table: article
-    name: author
-    using:
-      foreign_key_constraint_on: author_id

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

@@ -5,5 +5,3 @@ args:
     cascade: true
     sql: |
       DROP TABLE "user";
-      DROP TABLE "article";
-      DROP TABLE "author";

server/tests-py/test_graphql_queries.py

@@ -1127,6 +1127,7 @@ def dir(cls):
     def test_unauth_role(self, hge_ctx, transport):
         check_query_f(hge_ctx, self.dir() + '/unauthorized_role.yaml', transport, False)
 
+@pytest.mark.parametrize("backend", ['postgres', 'mssql'])
 @usefixtures('per_class_tests_db_state')
 class TestGraphQLExplain:
     @classmethod
@@ -1143,27 +1144,15 @@ def test_simple_query_as_user(self, hge_ctx, backend):
         st_code, resp = hge_ctx.v1GraphqlExplain(q, {"x-hasura-role": "random_user"})
         assert st_code == 400, resp
 
-    @pytest.mark.parametrize("backend", ['postgres', 'mssql'])
     def test_simple_query_as_admin_with_user_role(self, hge_ctx, backend):
         self.with_admin_secret(hge_ctx, self.dir() + hge_ctx.backend_suffix('/permissions_query') + ".yaml")
 
-    @pytest.mark.parametrize("backend", ['postgres', 'mssql'])
     def test_simple_query(self, hge_ctx, backend):
         self.with_admin_secret(hge_ctx, self.dir() + hge_ctx.backend_suffix('/simple_query') + ".yaml")
 
-    @pytest.mark.parametrize("backend", ['postgres', 'mssql'])
     def test_permissions_query(self, hge_ctx, backend):
         self.with_admin_secret(hge_ctx, self.dir() + hge_ctx.backend_suffix('/permissions_query') + ".yaml")
 
-    def test_limit_query(self, hge_ctx):
-        self.with_admin_secret(hge_ctx, self.dir() + '/limit_query.yaml')
-
-    def test_limit_orderby_column_query(self, hge_ctx):
-        self.with_admin_secret(hge_ctx, self.dir() + '/limit_orderby_column_query.yaml')
-
-    def test_limit_orderby_relationship_query(self, hge_ctx):
-        self.with_admin_secret(hge_ctx, self.dir() + '/limit_orderby_relationship_query.yaml')
-
     def with_admin_secret(self, hge_ctx, f, hdrs=None, req_st=200):
         conf = get_conf_f(f)
         admin_secret = hge_ctx.hge_key