SELECT FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS empty set when specific privileges on table

Step to reproduce :

Create a new database:

CREATE DATABASE test_db;

Create two tables with foreign keys (optional but it also shows that not only primary keys are not returned):

 CREATE TABLE `client` (

  `id` int(11) NOT NULL,

  `name` varchar(25) DEFAULT NULL,

  PRIMARY KEY (`id`)

);

CREATE TABLE `order` (

  `id` int(11) NOT NULL,

  `client_id` int(11) DEFAULT NULL,

  PRIMARY KEY (`id`),

  KEY `client_id` (`client_id`),

  CONSTRAINT `fk_order_client` FOREIGN KEY (`client_id`) REFERENCES `client` (`id`)

);

Create a new user with no specific privileges:

CREATE USER test;

Connect as user test and select table constraints:

SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS where TABLE_SCHEMA = 'test_db';

Result:

Grant SELECT privilege on test_db table to the test user:

GRANT SELECT ON test_db.* to test;

Select table constraints again:

SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS where TABLE_SCHEMA = 'test_db';

Result:

Empty set (0.0007 sec)

Additional informations

I have tested all privileges and my observations is that the user need at least one of this privileges on the table to get back a result set (or none at all):

ALTER, CREATE, DELETE, DROP, INDEX, INSERT, UPDATE, REFERENCES, TRIGGER, SHOW VIEW