SELECT
    'postgresql' AS dbms,
    t.table_catalog,
    t.table_schema,
    t.table_name,
    c.column_name,
    c.ordinal_position,
    c.data_type,
    c.character_maximum_length,
    n.constraint_type,
    k2.table_schema,
    k2.table_name,
    k2.column_name
FROM
    information_schema.tables t
    NATURAL
    LEFT JOIN information_schema.columns c
    LEFT JOIN (information_schema.key_column_usage k
    NATURAL JOIN information_schema.table_constraints n
    NATURAL
    LEFT JOIN information_schema.referential_constraints r)
ON c.table_catalog = k.table_catalog
AND c.table_schema = k.table_schema
AND c.table_name = k.table_name
AND c.column_name = k.column_name
    LEFT JOIN information_schema.key_column_usage k2 ON k.position_in_unique_constraint = k2.ordinal_position
    AND r.unique_constraint_catalog = k2.constraint_catalog
    AND r.unique_constraint_schema = k2.constraint_schema
    AND r.unique_constraint_name = k2.constraint_name
WHERE
    t.TABLE_TYPE = 'BASE TABLE'
    AND t.table_schema NOT IN ('information_schema', 'pg_catalog');