override detected relationships

src/PostgREST/DbStructure.hs

@@ -93,17 +93,33 @@ queryDbStructure schemas extraSearchPath prepared = do
   cRels   <- SQL.statement mempty $ allComputedRels prepared
 
   let tabsWViewsPks = addViewPrimaryKeys tabs keyDeps
-      rels          = relsToMap $ addO2MRels $ addM2MRels tabsWViewsPks $ addViewM2ORels keyDeps m2oRels
-      newRels       = HM.union (HM.fromList $ map addKey cRels) rels -- TODO: currently replacing all the relationships for a single table
+      rels          = addO2MRels $ addM2MRels tabsWViewsPks $ addViewM2ORels keyDeps m2oRels
 
   return $ removeInternal schemas $ DbStructure {
       dbTables = tabsWViewsPks
-    , dbRelationships = newRels
+    , dbRelationships = getOverrideRelationshipsMap rels cRels
     , dbProcs = procs
     }
+
+-- | overrides detected relationships with the computed relationships and gets the RelationshipsMap
+getOverrideRelationshipsMap :: [Relationship] -> [Relationship] -> RelationshipsMap
+getOverrideRelationshipsMap rels cRels =
+  sort <$> deformedRelMap patchedRels
   where
-    relsToMap = map sort . HM.fromListWith (++) . map addKey
-    addKey rel = ((relTable rel, qiSchema $ relForeignTable rel), [rel])
+    -- there can only be a single (table_type, func_name) pair in a function definition `test.function(table_type)`, so we use HM.fromList to disallow duplicates
+    computedRels  = HM.fromList $ relMapKey <$> cRels
+    -- here we override the detected relationships with the user computed relationships, HM.union makes sure computedRels prevail
+    patchedRels   = HM.union computedRels (relsMap rels)
+    relsMap = HM.fromListWith (++) . fmap relMapKey
+    relMapKey rel = case rel of
+      Relationship{relTable,relForeignTable} -> ((relTable, relForeignTable), [rel])
+      -- we use (relTable, relFunction) as key to override detected relationships with the function name
+      ComputedRelationShip{relTable,relFunction} -> ((relTable, relFunction), [rel])
+    -- Since a relationship is between a table and foreign table, the logical way to index/search is by their table/ftable QualifiedIdentifier
+    -- However, because we allow searching a relationship by the columns of the foreign key(using the "column as target" disambiguation) we lose the
+    -- ability to index by the foreign table name, so we deform the key. TODO remove once support for "column as target" is gone.
+    deformedRelMap = HM.fromListWith (++) . fmap addDeformedRelKey . HM.toList
+    addDeformedRelKey ((relT, relFT), rls) = ((relT, qiSchema relFT), rls)
 
 -- | Remove db objects that belong to an internal schema(not exposed through the API) from the DbStructure.
 removeInternal :: [Schema] -> DbStructure -> DbStructure

src/PostgREST/Request/DbRequestBuilder.hs

@@ -190,7 +190,7 @@ findRel schema allRels origin target hint =
       O2M _ _ -> True
       _       -> False
     rels = filter (\case
-      ComputedRelationShip{relForeignTable} -> target == qiName relForeignTable
+      ComputedRelationShip{relFunction} -> target == qiName relFunction
       Relationship{..} ->
         -- In a self-relationship we have a single foreign key but two relationships with different cardinalities: M2O/O2M. For disambiguation, we use the convention of getting:
         -- TODO: handle one-to-one and many-to-many self-relationships