fix: Prevent infinite recursion with self-referencing views

Fixes PostgREST#2283

Signed-off-by: Wolfgang Walther <[email protected]>

CHANGELOG.md

@@ -14,6 +14,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
  - #2518, Fix a regression when embedding views where base tables have a different column order for FK columns - @wolfgangwalther
  - #2458, Fix a regression with the location header when inserting into views with PKs from multiple tables - @wolfgangwalther
  - #2356, Fix a regression in openapi output with mode follow-privileges - @wolfgangwalther
+ - #2283, Fix infinite recursion when loading schema cache with self-referencing view - @wolfgangwalther
 
 ### Deprecated
 

src/PostgREST/SchemaCache.hs

@@ -895,8 +895,13 @@ allViewsKeyDependencies =
           (entry->>'resorigcol')::int as resorigcol
         from target_entries
       ),
-      recursion as(
-        select r.*
+      -- CYCLE detection according to PG docs: https://www.postgresql.org/docs/current/queries-with.html#QUERIES-WITH-CYCLE
+      -- Can be replaced with CYCLE clause once PG v13 is EOL.
+      recursion(view_id, view_schema, view_name, view_column, resorigtbl, resorigcol, is_cycle, path) as(
+        select
+          r.*,
+          false,
+          ARRAY[resorigtbl]
         from results r
         where view_schema = ANY ($1)
         union all
@@ -906,9 +911,12 @@ allViewsKeyDependencies =
           view.view_name,
           view.view_column,
           tab.resorigtbl,
-          tab.resorigcol
+          tab.resorigcol,
+          tab.resorigtbl = ANY(path),
+          path || tab.resorigtbl
         from recursion view
         join results tab on view.resorigtbl=tab.view_id and view.resorigcol=tab.view_column
+        where not is_cycle
       )
       select
         sch.nspname as table_schema,

test/spec/fixtures/schema.sql

@@ -2902,3 +2902,7 @@ $$;
 
 create trigger ins instead of insert on with_multiple_pks
   for each row execute procedure with_multiple_pks_insert();
+
+-- issue https://github.com/PostgREST/postgrest/issues/2283
+create view self_recursive_view as table projects;
+create or replace view self_recursive_view as table self_recursive_view;