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案例:用Redis来存储关注关系
Redis提供了丰富的数据类型,比起关系型数据库或者简单的Key-Value存储(比如Memcached)来,Redis的数据模型与实际应用的数据模型更相近。比如下面说到的好友关系的存储,原作者使用了Redis的 Sets(集合)数据结构。
具体存储方式如下:对于每一个用户,其关注关系存储两份列表,一份为此用户关注的人的UID列表,另一份为此用户粉丝的UID列表,这两个列表都使用Sets(集合)。比如对于用户ID为123的用户,graph:user:123:following 保存的是其关注人的列表,graph:user:1:followed_by 保存的是关注他的人的列表。
下面是一个PHP代码的关注关系类,包括了常规的关注关系操作查询等方法,具体可看注释:- <?
- /*
- * This example would probably work best if you're using
- * an MVC framework, but it can be used standalone as well.
- *
- * This example also assumes you are using Predis, the excellent
- * PHP Redis library available here:
- * https://github.com/nrk/predis
- */
- class UserNode {
- // The user's ID, probably loaded from MySQL
- private $id;
- // The redis server configuration
- private $redis_config = array(
- array('host' => 'localhost', 'port' => 6379 )
- );
- // Stores the redis connection resource so that
- // we only need to connect to Redis once
- private $redis;
- public function __construct($userID) {
- $this->id = $userID;
- }
- private function redis() {
- if (!$this->redis) {
- $this->redis = new Predis\Client($redis_config);
- }
- return $this->redis;
- }
- /*
- * Makes this user follow the user with the given ID.
- * In order to stay efficient, we need to make a two-way
- * directed graph. This means when we follow a user, we also
- * say that that user is followed by this user, making a forward
- * and backword directed graph.
- */
- public function follow($user) {
- $this->redis()->sadd("graph:user:{$this->id}:following", $user);
- $this->redis()->sadd("graph:user:$user:followed_by", $this->id);
- }
- /*
- * Makes this user unfollow the user with the given ID.
- * First we check to make sure that we are actually following
- * the user we want to unfollow, then we remove both the forward
- * and backward references.
- */
- public function unfollow($user) {
- if ($this->is_following()) {
- $this->redis()->srem("graph:user:{$this->id}:following", $user);
- $this->redis()->srem("graph:user:$user:followed_by", $this->id);
- }
- }
- /*
- * Returns an array of user ID's that this user follows.
- */
- public function following() {
- return $this->redis()->smembers("graph:user:{$this->id}:following");
- }
- /*
- * Returns an array of user ID's that this user is followed by.
- */
- public function followed_by() {
- return $this->redis()->smembers("graph:user:{$this->id}:followed_by");
- }
- /*
- * Test to see if this user is following the given user or not.
- * Returns a boolean.
- */
- public function is_following($user) {
- return $this->redis()->sismember("graph:user:{$this->id}:following", $user);
- }
- /*
- * Test to see if this user is followed by the given user.
- * Returns a boolean.
- */
- public function is_followed_by($user) {
- return $this->redis()->sismember("graph:user:{$this->id}:followed_by", $user);
- }
- /*
- * Tests to see if the relationship between this user and the given user is mutual.
- */
- public function is_mutual($user) {
- return ($this->is_following($user) && $this->is_followed_by($user));
- }
- /*
- * Returns the number of users that this user is following.
- */
- public function follow_count() {
- return $this->redis()->scard("graph:user:{$this->id}:following");
- }
- /*
- * Retuns the number of users that follow this user.
- */
- public function follower_count() {
- return $this->redis()->scard("graph:user:{$this->id}:followed_by");
- }
- /*
- * Finds all users that the given users follow in common.
- * Returns an array of user IDs
- */
- public function common_following($users) {
- $redis = $this->redis();
- $users[] = $this->id;
- $keys = array();
- foreach ($users as $user) {
- $keys[] = "graph:user:{$user}:following";
- }
- return call_user_func_array(array($redis, "sinter"), $keys);
- }
- /*
- * Finds all users that all of the given users are followed by in common.
- * Returns an array of user IDs
- */
- public function common_followed_by($users) {
- $redis = $this->redis();
- $users[] = $this->id;
- $keys = array();
- foreach ($users as $user) {
- $keys[] = "graph:user:{$user}:followed_by";
- }
- return call_user_func_array(array($redis, "sinter"), $keys);
- }
- }
复制代码 下面是使用这个类来操作关注关系的例子:
- <?
- // create two user nodes, assume for this example
- // they're users with no social graph entries.
- $user1 = UserNode(1);
- $user2 = UserNode(2);
- $user1->follows(); // array()
- // add some followers
- $user1->follow(2);
- $user1->follow(3);
- // now check the follow list
- $user1->follows(); // array(2, 3)
- // now we can also do:
- $user2->followed_by(); // array(1)
- // if we do this...
- $user2->follow(3);
- // then we can do this to see which people users #1 and #2 follow in common
- $user1->common_following(2); // array(3
复制代码 )来源:blog.meltingice.net
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