Postgres: find all FK constraints associated with a given PK
Does the following query work for you?
SELECT nr.nspname AS table_schema,
        r.relname AS table_name,
        c.conname AS constraint_name,
        split_part ( split_part ( pg_get_constraintdef ( c.oid ), '(', 2 ), ')', 1 ) AS column_names,
        nr2.nspname AS r_table_schema,
        r2.relname AS r_table_name,
        split_part ( split_part ( pg_get_constraintdef ( c.oid ), '(', 3 ), ')', 1 ) AS r_column_names,
        CASE c.confmatchtype
            WHEN 'f' THEN 'MATCH FULL '
            WHEN 'p' THEN 'MATCH PARTIAL '
            WHEN 'u' THEN 'MATCH NONE '
            ELSE ''
            END
            || CASE c.confupdtype
                WHEN 'c' THEN 'ON UPDATE CASCADE '
                WHEN 'n' THEN 'ON UPDATE SET NULL '
                WHEN 'd' THEN 'ON UPDATE SET DEFAULT '
                WHEN 'r' THEN 'ON UPDATE RESTRICT '
                WHEN 'a' THEN 'ON UPDATE NO ACTION '
                ELSE ''
                END
            || CASE c.confdeltype
                WHEN 'c' THEN 'ON DELETE CASCADE'
                WHEN 'n' THEN 'ON DELETE SET NULL'
                WHEN 'd' THEN 'ON DELETE SET DEFAULT'
                WHEN 'r' THEN 'ON DELETE RESTRICT'
                WHEN 'a' THEN 'ON DELETE NO ACTION'
                ELSE ''
                END AS constraint_rule,
        d.description AS comments
    FROM pg_class r
    INNER JOIN pg_namespace nr
        ON ( nr.oid = r.relnamespace )
    INNER JOIN pg_constraint c
        ON ( c.conrelid = r.oid )
    LEFT OUTER JOIN pg_description d
        ON ( d.objoid = c.oid )
    INNER JOIN pg_catalog.pg_class r2
        ON ( r2.oid = c.confrelid )
    INNER JOIN pg_namespace nr2
        ON ( nr2.oid = r2.relnamespace )
    WHERE r.relkind = 'r'
        AND c.contype = 'f'
        --AND nr.nspname = ?
        --AND r.relname = ?
        AND nr2.nspname = ?
        AND r2.relname = ?