Add isParent flag to O2O rels to identify which one has the FK

src/PostgREST/Error.hs

@@ -369,7 +369,7 @@ compressedRel Relationship{..} =
             "cardinality" .= ("many-to-one" :: Text)
           , "relationship" .= (cons <> " using " <> qiName relTable <> fmtEls (fst <$> relColumns) <> " and " <> qiName relForeignTable <> fmtEls (snd <$> relColumns))
           ]
-        O2O cons relColumns -> [
+        O2O cons relColumns _ -> [
             "cardinality" .= ("one-to-one" :: Text)
           , "relationship" .= (cons <> " using " <> qiName relTable <> fmtEls (fst <$> relColumns) <> " and " <> qiName relForeignTable <> fmtEls (snd <$> relColumns))
           ]
@@ -386,7 +386,7 @@ relHint rels = T.intercalate ", " (hintList <$> rels)
       case relCardinality of
         M2M Junction{..} -> buildHint (qiName junTable)
         M2O cons _       -> buildHint cons
-        O2O cons _       -> buildHint cons
+        O2O cons _ _     -> buildHint cons
         O2M cons _       -> buildHint cons
     -- An ambiguousness error cannot happen for computed relationships TODO refactor so this mempty is not needed
     hintList ComputedRelationship{} = mempty

src/PostgREST/Plan.hs

@@ -508,7 +508,7 @@ getJoinConditions tblAlias parentAlias Relationship{relTable=qi,relForeignTable=
       toJoinCondition parentAlias tblAlias tN ftN <$> cols
     M2O _ cols ->
       toJoinCondition parentAlias tblAlias tN ftN <$> cols
-    O2O _ cols ->
+    O2O _ cols _ ->
       toJoinCondition parentAlias tblAlias tN ftN <$> cols
   where
     QualifiedIdentifier{qiSchema=tSchema, qiName=tN} = qi
@@ -533,20 +533,20 @@ findRel schema allRels origin target hint =
     rs  -> Left $ AmbiguousRelBetween origin target rs
   where
     matchFKSingleCol hint_ card = case card of
-      O2M _ [(col, _)] -> hint_ == col
-      M2O _ [(col, _)] -> hint_ == col
-      O2O _ [(col, _)] -> hint_ == col
-      _                -> False
+      O2M _ [(col, _)]   -> hint_ == col
+      M2O _ [(col, _)]   -> hint_ == col
+      O2O _ [(col, _)] _ -> hint_ == col
+      _                  -> False
     matchFKRefSingleCol hint_ card  = case card of
-      O2M _ [(_, fCol)] -> hint_ == fCol
-      M2O _ [(_, fCol)] -> hint_ == fCol
-      O2O _ [(_, fCol)] -> hint_ == fCol
-      _                 -> False
+      O2M _ [(_, fCol)]   -> hint_ == fCol
+      M2O _ [(_, fCol)]   -> hint_ == fCol
+      O2O _ [(_, fCol)] _ -> hint_ == fCol
+      _                   -> False
     matchConstraint tar card = case card of
-      O2M cons _ -> tar == cons
-      M2O cons _ -> tar == cons
-      O2O cons _ -> tar == cons
-      _          -> False
+      O2M cons _   -> tar == cons
+      M2O cons _   -> tar == cons
+      O2O cons _ _ -> tar == cons
+      _            -> False
     matchJunction hint_ card = case card of
       M2M Junction{junTable} -> hint_ == qiName junTable
       _                      -> False
@@ -990,7 +990,7 @@ inferColsEmbedNeeds (Node ReadPlan{select} forest) pkCols
           Just $ fst <$> cols
         Node ReadPlan{relToParent=Just Relationship{relCardinality=M2O _ cols}} _ ->
           Just $ fst <$> cols
-        Node ReadPlan{relToParent=Just Relationship{relCardinality=O2O _ cols}} _ ->
+        Node ReadPlan{relToParent=Just Relationship{relCardinality=O2O _ cols _}} _ ->
           Just $ fst <$> cols
         Node ReadPlan{relToParent=Just Relationship{relCardinality=M2M Junction{junColsSource=cols}}} _ ->
           Just $ fst <$> cols

src/PostgREST/Response/OpenAPI.hs

@@ -114,9 +114,9 @@ makeProperty tbl rels col = (colName col, Inline s)
         relsSortedByIsView = sortOn relFTableIsView [ r | r@Relationship{} <- searchedRels]
         -- Finds the relationship that has a single column foreign key
         rel = find (\case
-          Relationship{relCardinality=(M2O _ relColumns)} -> [colName col] == (fst <$> relColumns)
-          Relationship{relCardinality=(O2O _ relColumns)} -> [colName col] == (fst <$> relColumns)
-          _                                               -> False
+          Relationship{relCardinality=(M2O _ relColumns)}       -> [colName col] == (fst <$> relColumns)
+          Relationship{relCardinality=(O2O _ relColumns False)} -> [colName col] == (fst <$> relColumns)
+          _                                                     -> False
           ) relsSortedByIsView
         fCol = (headMay . (\r -> snd <$> relColumns (relCardinality r)) =<< rel)
         fTbl = qiName . relForeignTable <$> rel

src/PostgREST/SchemaCache.hs

@@ -252,7 +252,7 @@ decodeRels :: HD.Result [Relationship]
 decodeRels =
  HD.rowList relRow
  where
-  relRow = (\(qi1, qi2, isSelf, constr, cols, isOneToOne) -> Relationship qi1 qi2 isSelf ((if isOneToOne then O2O else M2O) constr cols) False False) <$> row
+  relRow = (\(qi1, qi2, isSelf, constr, cols, isOneToOne)-> Relationship qi1 qi2 isSelf (if isOneToOne then O2O constr cols False else M2O constr cols) False False) <$> row
   row =
     (,,,,,) <$>
     (QualifiedIdentifier <$> column HD.text <*> column HD.text) <*>
@@ -518,21 +518,22 @@ addViewM2OAndO2ORels :: [ViewKeyDependency] -> [Relationship] -> [Relationship]
 addViewM2OAndO2ORels keyDeps rels =
   rels ++ concatMap viewRels rels
   where
-    isM2O card = case card of {M2O _ _ -> True; _ -> False;}
-    isO2O card = case card of {O2O _ _ -> True; _ -> False;}
+    isM2O card = case card of {M2O _ _       -> True; _ -> False;}
+    isO2O card = case card of {O2O _ _ False -> True; _ -> False;}
     viewRels Relationship{relTable,relForeignTable,relCardinality=card} =
       if isM2O card || isO2O card then
       let
         cons = relCons card
         relCols = relColumns card
+        buildCard cns cls = if isM2O card then M2O cns cls else O2O cns cls False
         viewTableRels = filter (\ViewKeyDependency{keyDepTable, keyDepCons, keyDepType} -> keyDepTable == relTable        && keyDepCons == cons && keyDepType == FKDep)    keyDeps
         tableViewRels = filter (\ViewKeyDependency{keyDepTable, keyDepCons, keyDepType} -> keyDepTable == relForeignTable && keyDepCons == cons && keyDepType == FKDepRef) keyDeps
       in
         [ Relationship
             (keyDepView vwTbl)
             relForeignTable
             False
-            ((if isM2O card then M2O else O2O) cons $ zipWith (\(_, vCol) (_, fCol)-> (vCol, fCol)) keyDepColsVwTbl relCols)
+            (buildCard cons $ zipWith (\(_, vCol) (_, fCol)-> (vCol, fCol)) keyDepColsVwTbl relCols)
             True
             False
         | vwTbl <- viewTableRels
@@ -542,7 +543,7 @@ addViewM2OAndO2ORels keyDeps rels =
             relTable
             (keyDepView tblVw)
             False
-            ((if isM2O card then M2O else O2O) cons $ zipWith (\(tCol, _) (_, vCol) -> (tCol, vCol)) relCols keyDepColsTblVw)
+            (buildCard cons $ zipWith (\(tCol, _) (_, vCol) -> (tCol, vCol)) relCols keyDepColsTblVw)
             False
             True
         | tblVw <- tableViewRels
@@ -557,7 +558,7 @@ addViewM2OAndO2ORels keyDeps rels =
             vw1
             vw2
             (vw1 == vw2)
-            ((if isM2O card then M2O else O2O) cons $ zipWith (\(_, vcol1) (_, vcol2) -> (vcol1, vcol2)) keyDepColsVwTbl keyDepColsTblVw)
+            (buildCard cons $ zipWith (\(_, vcol1) (_, vcol2) -> (vcol1, vcol2)) keyDepColsVwTbl keyDepColsTblVw)
             True
             True
         | vwTbl <- viewTableRels
@@ -572,7 +573,7 @@ addInverseRels :: [Relationship] -> [Relationship]
 addInverseRels rels =
   rels ++
   [ Relationship ft t isSelf (O2M cons (swap <$> cols)) fTableIsView tableIsView | Relationship t ft isSelf (M2O cons cols) tableIsView fTableIsView <- rels ] ++
-  [ Relationship ft t isSelf (O2O cons (swap <$> cols)) fTableIsView tableIsView | Relationship t ft isSelf (O2O cons cols) tableIsView fTableIsView <- rels ]
+  [ Relationship ft t isSelf (O2O cons (swap <$> cols) (not isParent)) fTableIsView tableIsView | Relationship t ft isSelf (O2O cons cols isParent) tableIsView fTableIsView <- rels ]
 
 -- | Adds a m2m relationship if a table has FKs to two other tables and the FK columns are part of the PK columns
 addM2MRels :: TablesMap -> [Relationship] -> [Relationship]

src/PostgREST/SchemaCache/Relationship.hs

@@ -44,8 +44,8 @@ data Cardinality
   -- ^ one-to-many
   | M2O {relCons :: FKConstraint, relColumns :: [(FieldName, FieldName)]}
   -- ^ many-to-one
-  | O2O {relCons :: FKConstraint, relColumns :: [(FieldName, FieldName)]}
-  -- ^ one-to-one, this is a refinement over M2O so operating on it is pretty much the same as M2O
+  | O2O {relCons :: FKConstraint, relColumns :: [(FieldName, FieldName)], isParent :: Bool}
+  -- ^ one-to-one, this is a refinement over M2O, operating on it is pretty much the same as M2O when isParent == False
   | M2M Junction
   -- ^ many-to-many
   deriving (Eq, Show, Ord, Generic, JSON.ToJSON)
@@ -67,7 +67,7 @@ type RelationshipsMap = HM.HashMap (QualifiedIdentifier, Schema)  [Relationship]
 
 relIsToOne :: Relationship -> Bool
 relIsToOne rel = case rel of
-  Relationship{relCardinality=M2O _ _} -> True
-  Relationship{relCardinality=O2O _ _} -> True
-  ComputedRelationship{relToOne=True}  -> True
-  _                                    -> False
+  Relationship{relCardinality=M2O {}} -> True
+  Relationship{relCardinality=O2O {}} -> True
+  ComputedRelationship{relToOne=True} -> True
+  _                                   -> False