Single-column natural primary keys

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with keys as (select 
(select nspname from pg_namespace where oid=c.relnamespace) as key_schema,
c.relname as key_table, 
c.oid as key_table_oid,
o.conkey AS key_col
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
where o.contype in ('p') and cardinality(o.conkey)=1),
keys_unnest as (select key_schema, key_table, key_table_oid, key_col, key_col_num, ordin
from keys, unnest(keys.key_col) with ordinality as k(key_col_num, ordin)),
keys_with_names AS (select key_schema, key_table, a_key.attname as key_col
from keys_unnest k inner join pg_attribute a_key on k.key_col_num = a_key.attnum and k.key_table_oid = a_key.attrelid and a_key.attisdropped = false
),
fk as (select 
(select nspname from pg_namespace where oid=c.relnamespace) as key_schema,
c.relname as key_table, 
c.oid as key_table_oid,
o.conkey AS key_col
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
where o.contype='f'),
fk_unnest as (select key_schema, key_table, key_table_oid, key_col, key_col_num, ordin
from fk, unnest(fk.key_col) with ordinality as k(key_col_num, ordin)),
fk_with_names AS (select key_schema, key_table, a_key.attname as key_col
from fk_unnest k inner join pg_attribute a_key on k.key_col_num = a_key.attnum and k.key_table_oid = a_key.attrelid and a_key.attisdropped = false),
key_not_fk AS (select key_schema, key_table, key_col
from keys_with_names
except select key_schema, key_table, key_col
from fk_with_names)
SELECT c.table_schema, c.table_name , c.column_name, 
CASE WHEN c.data_type ILIKE 'character%' AND c.character_maximum_length IS NOT NULL THEN c.data_type || '(' || c.character_maximum_length::text || ')'
WHEN c.data_type ILIKE 'timestamp%' AND c.datetime_precision IS NOT NULL THEN c.data_type || '(' || c.datetime_precision || ')'
WHEN c.data_type ILIKE 'numeric%' AND c.numeric_precision IS NOT NULL THEN c.data_type || '(' || c.numeric_precision::text || ',' ||coalesce(c.numeric_scale,0)::text || ')'
WHEN c.data_type ILIKE 'interval%' AND c.interval_type IS NOT NULL THEN c.data_type || '(' || c.interval_type::text || ')'
WHEN c.data_type='USER-DEFINED' THEN c.udt_schema || '.' || c.udt_name 
ELSE c.data_type END AS data_type
FROM information_schema.columns c
LEFT JOIN information_schema.domains d USING (domain_schema, domain_name)
INNER JOIN information_schema.schemata s
ON c.table_schema=s.schema_name
WHERE ((coalesce (c.column_default, d.domain_default) NOT ILIKE '%nextval%' OR coalesce (c.column_default, d.domain_default) IS NULL) AND c.is_identity='NO')
AND (c.table_schema = 'public'
OR s.schema_owner<>'postgres')
AND EXISTS (SELECT *
FROM key_not_fk AS k
WHERE k.key_schema=c.table_schema
AND k.key_table=c.table_name
AND k.key_col=c.column_name)
ORDER BY table_schema, table_name;