如何设计一个高性能的MySQL表结构来实现推荐系统功能？

id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(255) NOT NULL,
gender ENUM('male', 'female') NOT NULL,
age INT NOT NULL,
...

id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(255) NOT NULL,
category ENUM('book', 'movie', 'music', ...) NOT NULL,
...

id INT PRIMARY KEY AUTO_INCREMENT,
user_id INT NOT NULL,
item_id INT NOT NULL,
action_type ENUM('click', 'collect', 'purchase', ...) NOT NULL,
action_time DATETIME NOT NULL,
...

id INT PRIMARY KEY AUTO_INCREMENT,
user_id INT NOT NULL,
item_id INT NOT NULL,
score FLOAT NOT NULL,
...

import MySQLdb

# 连接到MySQL数据库
db = MySQLdb.connect(host='localhost', user='root', passwd='password', db='recommend')

# 创建光标对象
cursor = db.cursor()

# 查询用户最近点击的物品
user_id = 1
sql = "SELECT item_id FROM action WHERE user_id=%s AND action_type='click' ORDER BY action_time DESC LIMIT 10"
cursor.execute(sql, (user_id,))
recently_viewed = [row[0] for row in cursor.fetchall()]

# 查询与用户最近点击的物品相似的物品
sql = "SELECT item_id, COUNT(*) AS similarity_score FROM action WHERE user_id<>%s AND item_id IN %s AND action_type='click' GROUP BY item_id ORDER BY similarity_score DESC LIMIT 10"
cursor.execute(sql, (user_id, tuple(recently_viewed)))
similar_items = [row[0] for row in cursor.fetchall()]

# 将推荐结果插入推荐结果表
sql = "INSERT INTO recommendation (user_id, item_id, score) VALUES (%s, %s, %s)"
for item_id in similar_items:
    cursor.execute(sql, (user_id, item_id, 1.0))

# 提交事务
db.commit()

# 关闭数据库连接
db.close()