Add check "Duplicated foreign keys"

[mfvanek]

See article https://habr.com/ru/articles/803841/
Part "FK возможно совпадают или устарели"

WITH
-- объединяем ограничения FK с атрибутами, которые в них задействованы
fk_with_attributes AS (
        SELECT
            c.conname as fk_name,
            c.conrelid,
            c.confrelid,
            fk_conkey.conkey_order AS att_order,
            fk_conkey.conkey_number,
            fk_confkey.confkey_number,
            rel_att.attname AS rel_att_name,
            rel_att.atttypid AS rel_att_type_id,
            rel_att.atttypmod AS rel_att_type_mod,
            rel_att.attnotnull AS rel_att_notnull,
            frel_att.attname AS frel_att_name,
            frel_att.atttypid AS frel_att_type_id,
            frel_att.atttypmod AS frel_att_type_mod,
            frel_att.attnotnull AS frel_att_notnull
        FROM pg_catalog.pg_constraint AS c
            CROSS JOIN LATERAL UNNEST(c.conkey) WITH ORDINALITY AS fk_conkey(conkey_number, conkey_order)
            LEFT JOIN LATERAL UNNEST(c.confkey) WITH ORDINALITY AS fk_confkey(confkey_number, confkey_order)
                ON fk_conkey.conkey_order = fk_confkey.confkey_order
            LEFT JOIN pg_catalog.pg_attribute AS rel_att
                ON rel_att.attrelid = c.conrelid AND rel_att.attnum = fk_conkey.conkey_number
            LEFT JOIN pg_catalog.pg_attribute AS frel_att
                ON frel_att.attrelid = c.confrelid AND frel_att.attnum = fk_confkey.confkey_number
        WHERE c.contype IN ('f')
    ),
    --
    fk_with_attributes_grouped AS (
        SELECT
            fk_name,
            conrelid,
            confrelid,
            array_agg (rel_att_name order by att_order) as rel_att_names,
            array_agg (frel_att_name order by att_order) as frel_att_names
        FROM fk_with_attributes
        GROUP BY 1, 2, 3
    )
SELECT
    r_from.relname,  -- ссылающееся отношение
    c1.fk_name,      -- наименование ограничения fk
    c2.fk_name       -- наименование ограничения fk (потенцильный дубль)
FROM fk_with_attributes_grouped AS c1
    INNER JOIN fk_with_attributes_grouped AS c2 ON c1.fk_name < c2.fk_name 
        AND c1.conrelid = c2.conrelid AND c1.confrelid = c2.confrelid
        AND c1.rel_att_names = c2.rel_att_names
    INNER JOIN pg_catalog.pg_class AS r_from ON r_from.oid = c1.conrelid

Similar to https://github.com/mfvanek/pg-index-health-sql/blob/master/sql/duplicated_indexes.sql