Comment puis-je améliorer cette requête?

Question

Il y a environ un an, j'ai introduit une requête qui renvoie une sorte de jeu de données "des clients également achetés". À l'époque, il s'est déroulé assez vite cependant, ces derniers temps, il est devenu très lent, prenant parfois jusqu'à 5 secondes ou plus.

SELECT p.*, COUNT(*) AS total
FROM orders_products AS op
JOIN products AS p ON p.products_id = op.products_id
JOIN (
  SELECT orders_id
  FROM orders_products
  WHERE products_id = 100
) AS opf ON opf.orders_id = op.orders_id
WHERE op.products_id <> 100
GROUP BY products_id
ORDER BY total DESC
LIMIT 5;

Sortie de explain extended:

+------+-------------+-----------------+--------+-----------------------+-------------+---------+------------------------------------+------+----------+---------------------------------+
| id   | select_type | table           | type   | possible_keys         | key         | key_len | ref                                | rows | filtered | Extra                           |
+------+-------------+-----------------+--------+-----------------------+-------------+---------+------------------------------------+------+----------+---------------------------------+
|    1 | SIMPLE      | orders_products | ref    | products_id,orders_id | products_id | 4       | const                              | 4511 |   100.00 | Using temporary; Using filesort |
|    1 | SIMPLE      | op              | ref    | products_id,orders_id | orders_id   | 4       | database.orders_products.orders_id |    2 |   100.00 | Using where                     |
|    1 | SIMPLE      | p               | eq_ref | PRIMARY               | PRIMARY     | 4       | database.op.products_id            |    1 |   100.00 |                                 |
+------+-------------+-----------------+--------+-----------------------+-------------+---------+--------------------------------------+------+----------+-------------------------------+

SHOW CREATE TABLE products:

+----------+----------------------------------------------------------------+
| Table    | Create Table                                                   
+----------+----------------------------------------------------------------+
| products | CREATE TABLE `products` (
  `products_id` int(11) NOT NULL AUTO_INCREMENT,
  `products_model` varchar(128) DEFAULT NULL,
  `products_price` decimal(15,4) NOT NULL DEFAULT '0.0000',
  `products_date_added` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  `products_last_modified` datetime DEFAULT NULL,
  `products_status` tinyint(1) NOT NULL DEFAULT '0',
  PRIMARY KEY (`products_id`),
  KEY `idx_products_date_added` (`products_date_added`),
  KEY `products_model` (`products_model`),
  KEY `products_price` (`products_price`),
  KEY `products_status` (`products_status`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+----------+----------------------------------------------------------------+

SHOW INDEXES FROM products

+----------+------------+----------------------------------+--------------+----------------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table    | Non_unique | Key_name                         | Seq_in_index | Column_name                | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+----------+------------+----------------------------------+--------------+----------------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| products |          0 | PRIMARY                          |            1 | products_id                | A         |        4356 |     NULL | NULL   |      | BTREE      |         |               |
| products |          1 | idx_products_date_added          |            1 | products_date_added        | A         |        4356 |     NULL | NULL   |      | BTREE      |         |               |
| products |          1 | products_model                   |            1 | products_model             | A         |        4356 |     NULL | NULL   | YES  | BTREE      |         |               |
| products |          1 | products_price                   |            1 | products_price             | A         |        1089 |     NULL | NULL   |      | BTREE      |         |               |
| products |          1 | products_status                  |            1 | products_status            | A         |           4 |     NULL | NULL   |      | BTREE      |         |               |
+----------+------------+----------------------------------+--------------+----------------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

SHOW CREATE TABLE orders_products:

+-----------------+--------------------------------------------------------+
| Table           | Create Table                                           
+-----------------+--------------------------------------------------------+
| orders_products | CREATE TABLE `orders_products` (
  `orders_products_id` int(11) NOT NULL AUTO_INCREMENT,
  `orders_id` int(11) NOT NULL DEFAULT '0',
  `products_id` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`orders_products_id`),
  KEY `products_id` (`products_id`),
  KEY `orders_id` (`orders_id`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+-----------------+--------------------------------------------------------+

SHOW INDEXES FROM orders_products

+-----------------+------------+-------------+--------------+--------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table           | Non_unique | Key_name    | Seq_in_index | Column_name        | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-----------------+------------+-------------+--------------+--------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| orders_products |          0 | PRIMARY     |            1 | orders_products_id | A         |     3134198 |     NULL | NULL   |      | BTREE      |         |               |
| orders_products |          1 | products_id |            1 | products_id        | A         |        5014 |     NULL | NULL   |      | BTREE      |         |               |
| orders_products |          1 | orders_id   |            1 | orders_id          | A         |     1567099 |     NULL | NULL   |      | BTREE      |         |               |
+-----------------+------------+-------------+--------------+--------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

Y a-t-il quelque chose d'évident qui me manque ici? En ce qui concerne la base de données, la base de données semble bien réglée. Nous dirigeons MariADB 5.5.30 sous le moteur de stockage InnODB / XTRADB.