Short cycles (tables)

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WITH fk as (select
o.conname,
(select nspname from pg_namespace where oid=f.relnamespace) as foreign_schema,
f.relname as foreign_table,
f.oid as foreign_table_oid,
o.confkey AS foreign_col,
(select nspname from pg_namespace where oid=c.relnamespace) as target_schema,
c.relname as target_table,
c.oid as target_table_oid,
o.conkey AS target_col,
CASE WHEN o.confupdtype='a' THEN 'NO ACTION'
WHEN o.confupdtype='r' THEN 'RESTRICT'
WHEN o.confupdtype='c' THEN 'CASCADE'
WHEN o.confupdtype='n' THEN 'SET NULL'
WHEN o.confupdtype='d' THEN 'SET DEFAULT' END AS on_update,
CASE WHEN o.confdeltype='a' THEN 'NO ACTION'
WHEN o.confdeltype='r' THEN 'RESTRICT'
WHEN o.confdeltype='c' THEN 'CASCADE'
WHEN o.confdeltype='n' THEN 'SET NULL'
WHEN o.confdeltype='d' THEN 'SET DEFAULT' END AS on_delete
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'
and condeferrable=false),
fk_unnest as (select conname, foreign_schema, foreign_table,  foreign_table_oid, foreign_col, foreign_col_num, target_schema, target_table, target_table_oid, target_col, target_col_num, ordin, on_update, on_delete
from fk, unnest(fk.foreign_col, fk. target_col) with ordinality as f(foreign_col_num, target_col_num, ordin)),
fk_with_names as (select conname, foreign_schema, foreign_table, a_foreign.attname as foreign_col, foreign_col_num, target_schema, target_table, a_target.attname as target_col,  target_col_num, on_update, on_delete
from fk_unnest fk inner join pg_attribute a_foreign on fk.foreign_col_num = a_foreign.attnum and fk.foreign_table_oid = a_foreign.attrelid and a_foreign.attisdropped = false
inner join pg_attribute a_target on fk.target_col_num = a_target.attnum and fk.target_table_oid = a_target.attrelid and a_target.attisdropped = false
where (fk.target_schema, fk.target_table, a_target.attname) IN (SELECT c.table_schema, c.table_name, c.column_name
FROM information_schema.columns AS c
WHERE c.is_nullable='NO')),
intersection as (select foreign_schema, foreign_table, target_schema, target_table
from fk_with_names
intersect select target_schema, target_table, foreign_schema, foreign_table
from fk_with_names),
cycles as (select foreign_schema, foreign_table, target_schema, target_table
from intersection
where ((foreign_schema=target_schema and foreign_table<>target_table)
or (foreign_schema<>target_schema)))
select target_schema, target_table, target_col, foreign_schema, foreign_table, foreign_col, on_update, on_delete, conname
from fk_with_names AS fwn
where exists (select *
from cycles
where cycles.foreign_schema=fwn.foreign_schema
and cycles.foreign_table=fwn.foreign_table
and cycles.target_schema=fwn.target_schema
and cycles.target_table=fwn.target_table)
and exists (select *
from cycles
where cycles.target_schema=fwn.foreign_schema
and cycles.target_table=fwn.foreign_table
and cycles.foreign_schema=fwn.target_schema
and cycles.foreign_table=fwn.target_table)
order by target_schema, target_table, foreign_schema, foreign_table;