fix: bad M2M embed on RPC

test/spec/fixtures/schema.sql

@@ -2996,3 +2996,24 @@ CREATE TABLE public.tb (
 
 CREATE VIEW test.va AS SELECT a1 FROM public.ta;
 CREATE VIEW test.vb AS SELECT b1 FROM public.tb;
+
+CREATE TABLE test.groups (
+    name text PRIMARY KEY
+);
+
+CREATE TABLE test.yards (
+    id bigint PRIMARY KEY
+);
+
+CREATE TABLE test.group_yard (
+    id bigint NOT NULL,
+    group_id text NOT NULL REFERENCES test.groups(name),
+    yard_id bigint NOT NULL REFERENCES test.yards(id),
+    PRIMARY KEY (id, group_id, yard_id)
+);
+
+CREATE FUNCTION test.get_yards() RETURNS SETOF test.yards
+LANGUAGE sql
+AS $$
+  select * from test.yards;
+$$;