Potentially missing PRIMARY KEY or UNIQUE constraints (based on foreign keys)

WITH f AS (select (select nspname from pg_namespace where oid=c.relnamespace) as target_ns,
c.relname as target_table
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
inner join pg_class f on f.oid = o.confrelid
where o.contype = 'f'),
non_key_columns AS (SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.columns c
WHERE (table_schema, table_name) IN (SELECT table_schema, table_name
FROM INFORMATION_SCHEMA.tables WHERE table_type='BASE TABLE') AND 
table_schema NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND schema_owner='postgres')
EXCEPT SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.key_column_usage kcu),
overlapping_key_columns AS (
SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.key_column_usage kcu
WHERE position_in_unique_constraint IS NULL
INTERSECT SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.key_column_usage kcu
WHERE position_in_unique_constraint IS NOT NULL)
SELECT t.table_schema, t.table_name
FROM INFORMATION_SCHEMA.tables t
INNER JOIN INFORMATION_SCHEMA.schemata s
ON t.table_schema=s.schema_name 
WHERE t.table_type='BASE TABLE' AND 
(t.table_schema = 'public' OR s.schema_owner<>'postgres')  AND
(SELECT Count(*) AS cnt FROM f WHERE t.table_schema=f.target_ns AND t.table_name=f.target_table)>=2 AND
NOT EXISTS (SELECT 1 FROM non_key_columns nkc WHERE nkc.table_schema=t.table_schema AND nkc.table_name=t.table_name) AND
NOT EXISTS (SELECT 1 FROM overlapping_key_columns okc WHERE okc.table_schema=t.table_schema AND okc.table_name=t.table_name)
ORDER BY t.table_schema, t.table_name;