fix: Detect all relationships when multiple view columns reference the same table column

Signed-off-by: Wolfgang Walther <walther@technowledgy.de>

CHANGELOG.md

@@ -26,6 +26,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
  - #2475, Disallow !inner on computed columns - @wolfgangwalther
  - #2285, Ignore leading and trailing spaces in column names when parsing the query string - @wolfgangwalther
  - #2545, Fix UPSERT with PostgreSQL 15 - @wolfgangwalther
+ - #2459, Fix embedding views with multiple references to the same base column - @wolfgangwalther
 
 ### Changed
 

src/PostgREST/SchemaCache.hs

@@ -66,12 +66,33 @@ data SchemaCache = SchemaCache
   deriving (Generic, JSON.ToJSON)
 
 -- | A view foreign key or primary key dependency detected on its source table
+-- Each column of the key could be referenced multiple times in the view, e.g.
+--
+-- create view projects_view as
+-- select
+--   id as id_1,
+--   id as id_2,
+--   id as id_3,
+--   name
+-- from projects
+--
+-- In this case, the keyDepCols mapping maps projects.id to all three of the columns:
+--
+-- [('id', ['id_1', 'id_2', 'id_3'])]
+--
+-- Depending on key type, we can then choose how to handle this case. Primary keys
+-- can arbitrarily choose one of the columns, but for foreign keys we need to create
+-- relationships for each possible mutations.
+--
+-- Previously, we stored a (FieldName, FieldName) tuple only, but then we had no
+-- way to make a difference between a multi-column-key and a single-column-key with multiple
+-- references in the view. Or even worse in the multi-column-key-multi-reference case...
 data ViewKeyDependency = ViewKeyDependency {
   keyDepTable :: QualifiedIdentifier
 , keyDepView  :: QualifiedIdentifier
 , keyDepCons  :: Text
 , keyDepType  :: KeyDep
-, keyDepCols  :: [(FieldName, FieldName)] -- ^ First element is the table column, second is the view column
+, keyDepCols  :: [(FieldName, [FieldName])] -- ^ First element is the table column, second is a list of view columns
 } deriving (Eq)
 data KeyDep
   = PKDep    -- ^ PK dependency
@@ -192,9 +213,9 @@ decodeViewKeyDeps =
     <*> compositeArrayColumn
         ((,)
         <$> compositeField HD.text
-        <*> compositeField HD.text)
+        <*> compositeFieldArray HD.text)
 
-viewKeyDepFromRow :: (Text,Text,Text,Text,Text,Text,[(Text, Text)]) -> ViewKeyDependency
+viewKeyDepFromRow :: (Text,Text,Text,Text,Text,Text,[(Text, [Text])]) -> ViewKeyDependency
 viewKeyDepFromRow (s1,t1,s2,v2,cons,consType,sCols) = ViewKeyDependency (QualifiedIdentifier s1 t1) (QualifiedIdentifier s2 v2) cons keyDep sCols
   where
     keyDep | consType == "p" = PKDep
@@ -394,19 +415,21 @@ addViewM2OAndO2ORels keyDeps rels =
             (keyDepView vwTbl)
             relForeignTable
             False
-            ((if isM2O card then M2O else O2O) cons $ zipWith (\(_, vCol) (_, fCol)-> (vCol, fCol)) (keyDepCols vwTbl) relCols)
+            ((if isM2O card then M2O else O2O) cons $ zipWith (\(_, vCol) (_, fCol)-> (vCol, fCol)) keyDepColsVwTbl relCols)
             True
             False
-        | vwTbl <- viewTableRels ]
+        | vwTbl <- viewTableRels
+        , keyDepColsVwTbl <- expandKeyDepCols $ keyDepCols vwTbl ]
         ++
         [ Relationship
             relTable
             (keyDepView tblVw)
             False
-            ((if isM2O card then M2O else O2O) cons $ zipWith (\(tCol, _) (_, vCol) -> (tCol, vCol)) relCols (keyDepCols tblVw))
+            ((if isM2O card then M2O else O2O) cons $ zipWith (\(tCol, _) (_, vCol) -> (tCol, vCol)) relCols keyDepColsTblVw)
             False
             True
-        | tblVw <- tableViewRels ]
+        | tblVw <- tableViewRels
+        , keyDepColsTblVw <- expandKeyDepCols $ keyDepCols tblVw ]
         ++
         [
           let
@@ -417,13 +440,16 @@ addViewM2OAndO2ORels keyDeps rels =
             vw1
             vw2
             (vw1 == vw2)
-            ((if isM2O card then M2O else O2O) cons $ zipWith (\(_, vcol1) (_, vcol2) -> (vcol1, vcol2)) (keyDepCols vwTbl) (keyDepCols tblVw))
+            ((if isM2O card then M2O else O2O) cons $ zipWith (\(_, vcol1) (_, vcol2) -> (vcol1, vcol2)) keyDepColsVwTbl keyDepColsTblVw)
             True
             True
         | vwTbl <- viewTableRels
-        , tblVw <- tableViewRels ]
+        , keyDepColsVwTbl <- expandKeyDepCols $ keyDepCols vwTbl
+        , tblVw <- tableViewRels
+        , keyDepColsTblVw <- expandKeyDepCols $ keyDepCols tblVw ]
       else []
     viewRels _ = []
+    expandKeyDepCols kdc = zip (fst <$> kdc) <$> sequenceA (snd <$> kdc)
 
 addInverseRels :: [Relationship] -> [Relationship]
 addInverseRels rels =
@@ -452,8 +478,14 @@ addViewPrimaryKeys tabs keyDeps =
     else tbl) <$> tabs
   where
     findViewPKCols sch vw =
-      concatMap (\(ViewKeyDependency _ _ _ _ pkCols) -> snd <$> pkCols) $
+      concatMap (\(ViewKeyDependency _ _ _ _ pkCols) -> takeFirstPK pkCols) $
       filter (\(ViewKeyDependency _ viewQi _ dep _) -> dep == PKDep && viewQi == QualifiedIdentifier sch vw) keyDeps
+    -- In the case of multiple reference to the same PK (see comment for ViewKeyDependency) we take the first reference available.
+    -- We assume this to be safe to do, because:
+    -- * We don't have any logic that requires the client to name a PK column (compared to the column hints in embedding for FKs),
+    --   so we don't need to know about the other references.
+    -- * We need to choose a single reference for each column, otherwise we'd output too many columns in location headers etc.
+    takeFirstPK pkCols = catMaybes $ head . snd <$> pkCols
 
 allTables :: PgVersion -> Bool -> SQL.Statement [Schema] TablesMap
 allTables pgVer =
@@ -917,22 +949,38 @@ allViewsKeyDependencies =
         from recursion view
         join results tab on view.resorigtbl=tab.view_id and view.resorigcol=tab.view_column
         where not is_cycle
+      ),
+      repeated_references as(
+        select
+          view_id,
+          view_schema,
+          view_name,
+          resorigtbl,
+          resorigcol,
+          array_agg(attname) as view_columns
+        from recursion
+        join pg_attribute vcol on vcol.attrelid = view_id and vcol.attnum = view_column
+        group by
+          view_id,
+          view_schema,
+          view_name,
+          resorigtbl,
+          resorigcol
       )
       select
         sch.nspname as table_schema,
         tbl.relname as table_name,
-        rec.view_schema,
-        rec.view_name,
+        rep.view_schema,
+        rep.view_name,
         pks_fks.conname as constraint_name,
         pks_fks.contype as constraint_type,
-        array_agg(row(col.attname, vcol.attname) order by pks_fks.ord) as column_dependencies
-      from recursion rec
-      join pg_class tbl on tbl.oid = rec.resorigtbl
-      join pg_attribute col on col.attrelid = tbl.oid and col.attnum = rec.resorigcol
-      join pg_attribute vcol on vcol.attrelid = rec.view_id and vcol.attnum = rec.view_column
-      join pg_namespace sch on sch.oid = tbl.relnamespace
+        array_agg(row(col.attname, view_columns) order by pks_fks.ord) as column_dependencies
+      from repeated_references rep
       join pks_fks using (resorigtbl, resorigcol)
-      group by sch.nspname, tbl.relname,  rec.view_schema, rec.view_name, pks_fks.conname, pks_fks.contype
+      join pg_class tbl on tbl.oid = rep.resorigtbl
+      join pg_attribute col on col.attrelid = tbl.oid and col.attnum = rep.resorigcol
+      join pg_namespace sch on sch.oid = tbl.relnamespace
+      group by sch.nspname, tbl.relname,  rep.view_schema, rep.view_name, pks_fks.conname, pks_fks.contype
       |]
 
 param :: HE.Value a -> HE.Params a

test/spec/Feature/Query/EmbedDisambiguationSpec.hs

@@ -120,6 +120,41 @@ spec =
           , matchHeaders = [matchContentTypeJson]
           }
 
+      it "errs with multiple references to the same composite key columns in a view" $
+        get "/i2459_composite_v2?select=*,i2459_composite_v1(*)" `shouldRespondWith`
+          [json|
+            {
+              "code": "PGRST201",
+              "details": [
+                {
+                  "cardinality": "many-to-one",
+                  "embedding": "i2459_composite_v2 with i2459_composite_v1",
+                  "relationship": "i2459_composite_t2_t1_a_t1_b_fkey using i2459_composite_v2(t1_a1, t1_b1) and i2459_composite_v1(a, b)"
+                },
+                {
+                  "cardinality": "many-to-one",
+                  "embedding": "i2459_composite_v2 with i2459_composite_v1",
+                  "relationship": "i2459_composite_t2_t1_a_t1_b_fkey using i2459_composite_v2(t1_a1, t1_b2) and i2459_composite_v1(a, b)"
+                },
+                {
+                  "cardinality": "many-to-one",
+                  "embedding": "i2459_composite_v2 with i2459_composite_v1",
+                  "relationship": "i2459_composite_t2_t1_a_t1_b_fkey using i2459_composite_v2(t1_a2, t1_b1) and i2459_composite_v1(a, b)"
+                },
+                {
+                  "cardinality": "many-to-one",
+                  "embedding": "i2459_composite_v2 with i2459_composite_v1",
+                  "relationship": "i2459_composite_t2_t1_a_t1_b_fkey using i2459_composite_v2(t1_a2, t1_b2) and i2459_composite_v1(a, b)"
+                }
+              ],
+              "hint": "Try changing 'i2459_composite_v1' to one of the following: 'i2459_composite_v1!i2459_composite_t2_t1_a_t1_b_fkey', 'i2459_composite_v1!i2459_composite_t2_t1_a_t1_b_fkey', 'i2459_composite_v1!i2459_composite_t2_t1_a_t1_b_fkey', 'i2459_composite_v1!i2459_composite_t2_t1_a_t1_b_fkey'. Find the desired relationship in the 'details' key.",
+              "message": "Could not embed because more than one relationship was found for 'i2459_composite_v2' and 'i2459_composite_v1'"
+            }
+          |]
+          { matchStatus  = 300
+          , matchHeaders = [matchContentTypeJson]
+          }
+
     context "disambiguating requests with embed hints" $ do
 
       context "using FK to specify the relationship" $ do
@@ -240,6 +275,20 @@ spec =
             [json| [ { "name": "site 1", "main_project_id": { "name": "big project 1" } } ] |]
             { matchHeaders = [matchContentTypeJson] }
 
+        it "can specify all view column names that reference the same base column" $ do
+          get "/i2459_simple_v1?select=*,i2459_simple_v2!t1_id1(*)" `shouldRespondWith`
+            [json| [] |]
+            { matchHeaders = [matchContentTypeJson] }
+          get "/i2459_simple_v1?select=*,i2459_simple_v2!t1_id2(*)" `shouldRespondWith`
+            [json| [] |]
+            { matchHeaders = [matchContentTypeJson] }
+          get "/i2459_simple_v2?select=*,i2459_simple_v1!t1_id1(*)" `shouldRespondWith`
+            [json| [] |]
+            { matchHeaders = [matchContentTypeJson] }
+          get "/i2459_simple_v2?select=*,i2459_simple_v1!t1_id2(*)" `shouldRespondWith`
+            [json| [] |]
+            { matchHeaders = [matchContentTypeJson] }
+
       context "using the junction to disambiguate the request" $
         it "can specify the junction of an m2m relationship" $ do
           get "/sites?select=*,big_projects!jobs(name)&site_id=in.(1,2)" `shouldRespondWith`
@@ -341,6 +390,14 @@ spec =
               }
             ]|] { matchHeaders = [matchContentTypeJson] }
 
+        it "can specify all view column names that reference the same base column" $ do
+          get "/i2459_self_v1?select=*,parent(*),grandparent(*)" `shouldRespondWith`
+            [json| [] |]
+            { matchHeaders = [matchContentTypeJson] }
+          get "/i2459_self_v2?select=*,parent(*),grandparent(*)" `shouldRespondWith`
+            [json| [] |]
+            { matchHeaders = [matchContentTypeJson] }
+
       context "two self reference foreign keys" $ do
         it "embeds parents" $
           get "/organizations?select=id,name,referee(id,name),auditor(id,name)&id=eq.3" `shouldRespondWith`
@@ -506,4 +563,3 @@ spec =
               }
             ]|]
           { matchHeaders = [matchContentTypeJson] }
-

test/spec/fixtures/schema.sql

@@ -2918,3 +2918,65 @@ $$ LANGUAGE sql STABLE;
 CREATE FUNCTION test.computed_projects(test.clients) RETURNS SETOF test.projects ROWS 1 AS $$
   SELECT * FROM test.projects WHERE client_id = $1.id;
 $$ LANGUAGE sql STABLE;
+
+-- issue https://github.com/PostgREST/postgrest/issues/2459
+create table public.i2459_simple_t1 (
+  id int primary key
+);
+
+create table public.i2459_simple_t2 (
+  t1_id int references public.i2459_simple_t1
+);
+
+create view i2459_simple_v1 as table public.i2459_simple_t1;
+
+create view i2459_simple_v2 as
+  select t1_id as t1_id1, t1_id as t1_id2 from public.i2459_simple_t2;
+
+
+create table public.i2459_composite_t1 (
+  primary key (a,b),
+  a int,
+  b int
+);
+
+create table public.i2459_composite_t2 (
+  t1_a int,
+  t1_b int,
+  constraint i2459_composite_t2_t1_a_t1_b_fkey foreign key (t1_a, t1_b) references public.i2459_composite_t1
+);
+
+create view i2459_composite_v1 as table public.i2459_composite_t1;
+
+create view i2459_composite_v2 as
+  select t1_a as t1_a1,
+         t1_b as t1_b1,
+         t1_a as t1_a2,
+         t1_b as t1_b2
+    from public.i2459_composite_t2;
+
+
+create table public.i2459_self_t (
+  id int primary key,
+  parent int references public.i2459_self_t,
+  type text
+);
+
+
+create view i2459_self_v1 as
+select parent.parent as grandparent,
+       child.parent,
+       child.id
+  from public.i2459_self_t as parent
+       join public.i2459_self_t as child
+         on child.parent = parent.id
+ where child.type = 'A';
+
+create view i2459_self_v2 as
+select parent.parent as grandparent,
+       child.parent,
+       child.id
+  from public.i2459_self_t as parent
+       join public.i2459_self_t as child
+         on child.parent = parent.id
+ where child.type = 'B';