结果缓存

MikroORM 有一个简单的结果缓存机制。它与 EntityManager 的那些方法一起工作：find()、findOne()、findAndCount()、findOneOrFail()、count()，以及 QueryBuilder 结果方法（包括 execute）。

¥MikroORM has a simple result caching mechanism. It works with those methods of EntityManager: find(), findOne(), findAndCount(), findOneOrFail(), count(), as well as with QueryBuilder result methods (including execute).

默认情况下，使用内存缓存，该缓存在整个 MikroORM 实例中共享。默认到期时间为 1 秒。

¥By default, in memory cache is used, that is shared for the whole MikroORM instance. Default expiration is 1 second.

const res = await em.find(Book, { author: { name: 'Jon Snow' } }, {
  populate: ['author', 'tags'],
  cache: 50, // set expiration to 50ms
  // cache: ['cache-key', 50], // set custom cache key and expiration
  // cache: true, // use default cache key and expiration
});

或使用查询构建器：

¥Or with query builder:

const res = await em.createQueryBuilder(Book)
  .where({ author: { name: 'Jon Snow' } })
  .cache()
  .getResultList();

我们可以在 ORM 配置中更改默认过期时间并提供自定义缓存适配器：

¥We can change the default expiration as well as provide custom cache adapter in the ORM configuration:

const orm = await MikroORM.init({
  resultCache: {
    // following options are the defaults
    adapter: MemoryCacheAdapter,
    expiration: 1000, // 1s
    options: {},
    // cache can be also enabled globally
    // global: 50, // 50ms
  },
  // ...
});

要清除缓存结果，我们需要使用显式缓存键加载它，稍后我们可以使用 em.clearCache(cacheKey) 方法。

¥To clear the cached result, we need to load it with explicit cache key, and later on we can use em.clearCache(cacheKey) method.

// set the cache key to 'book-cache-key', with expiration of 60s
const res = await em.find(Book, { ... }, { cache: ['book-cache-key', 60_000] });

// clear the cache key by name
await em.clearCache('book-cache-key');

自定义缓存适配器需要实现 CacheAdapter 接口。

¥Custom cache adapters need to implement CacheAdapter interface.

export interface CacheAdapter {

  /**

   * Gets the items under `name` key from the cache.
   */
  get(name: string): Promise<any>;

  /**

   * Sets the item to the cache. `origin` is used for cache invalidation and should reflect the change in data.
   */
  set(name: string, data: any, origin: string, expiration?: number): Promise<void>;

  /**

   * Removes the item from cache.
   */
  remove(name: string): Promise<void>;

  /**

   * Clears all items stored in the cache.
   */
  clear(): Promise<void>;

  /**

   * Called inside `MikroORM.close()` Allows graceful shutdowns (e.g. for redis).
   */
  close?(): Promise<void>;

}