with keys as (select 
o.conname,
(select nspname from pg_namespace where oid=m.relnamespace) as key_schema,
m.relname as key_table, 
m.oid as key_table_oid,
o.conkey AS key_col,
case when o.contype='p' then 'PRIMARY KEY' ELSE 'UNIQUE' END as contype
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
inner join pg_class m on m.oid = o.conrelid
where o.contype in ('p','u')  and o.conrelid in (select oid from pg_class c where c.relkind = 'r')),
keys_unnest as (select conname, key_schema, key_table, key_table_oid, key_col, key_col_num, ordin, contype
from keys, unnest(keys.key_col) with ordinality as k(key_col_num, ordin)),
keys_with_names as (select conname, key_schema, key_table, contype, array_agg(a_key.attname order by ordin) 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
group by conname, key_schema, key_table, contype)
SELECT format ('ALTER TABLE %1$I.%2$I DROP CONSTRAINT %3$I;', a.key_schema, a.key_table, CASE WHEN a.contype='PRIMARY KEY' THEN b.conname ELSE a.conname END) AS statements
from keys_with_names as a, keys_with_names as b
WHERE  a.key_schema=b.key_schema AND a.key_table=b.key_table AND
a.conname>b.conname AND
(a.key_col@>b.key_col AND b.key_col@>a.key_col)
UNION SELECT format ('ALTER TABLE %1$I.%2$I DROP CONSTRAINT %3$I;', a.key_schema, a.key_table, CASE WHEN a.contype='PRIMARY KEY' THEN b.conname ELSE a.conname END) AS statements
from keys_with_names as a, keys_with_names as b
WHERE  a.key_schema=b.key_schema AND a.key_table=b.key_table AND
a.conname>b.conname AND
(a.key_col@>b.key_col AND b.key_col@>a.key_col)
ORDER BY  statements;