如何建设企业电子商务网站,oracle数据库做的网站,动易网站开发的主要技术,做国际黄金看什么网站hibernate查询缓存介绍 现在#xff0c;我已经介绍了实体和集合缓存#xff0c;现在该研究查询缓存的工作原理了。 查询缓存与实体严格相关#xff0c;它在搜索条件和满足该特定查询过滤器的实体之间绘制关联。 像其他Hibernate功能一样#xff0c;查询缓存也不像人们想象… hibernate查询缓存 介绍 现在我已经介绍了实体和集合缓存现在该研究查询缓存的工作原理了。 查询缓存与实体严格相关它在搜索条件和满足该特定查询过滤器的实体之间绘制关联。 像其他Hibernate功能一样查询缓存也不像人们想象的那么琐碎。 实体模型 对于我们的测试用例我们将使用以下域模型 Post实体与Author 具有多对一关联并且两个实体都存储在第二级缓存中。 启用查询缓存 默认情况下查询缓存处于禁用状态要激活它我们需要提供以下Hibernate属性 properties.put(hibernate.cache.use_query_cache, Boolean.TRUE.toString()); 为了使Hibernate缓存给定的查询结果我们需要在创建Query时显式设置cachable查询属性 。 直读缓存 查询缓存是只读的 就像NONSTRICT_READ_WRITE并发策略一样 它只能使过时的条目无效。 在下一个示例中我们将缓存以下查询 private ListPost getLatestPosts(Session session) {return (ListPost) session.createQuery(select p from Post p order by p.createdOn desc).setMaxResults(10).setCacheable(true).list();
} 首先我们将使用以下测试案例来研究查询缓存的内部结构 doInTransaction(session - {LOGGER.info(Evict regions and run query);session.getSessionFactory().getCache().evictAllRegions();assertEquals(1, getLatestPosts(session).size());
});doInTransaction(session - {LOGGER.info(Check get entity is cached);Post post (Post) session.get(Post.class, 1L);
});doInTransaction(session - {LOGGER.info(Check query result is cached);assertEquals(1, getLatestPosts(session).size());
}); 该测试生成以下输出 QueryCacheTest - Evict regions and run queryStandardQueryCache - Checking cached query results in region: org.hibernate.cache.internal.StandardQueryCache
EhcacheGeneralDataRegion - Element for key sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2
is null
StandardQueryCache - Query results were not found in cacheselectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_
fromPost querycache0_
order byquerycache0_.created_on desc limit 10StandardQueryCache - Caching query results in region: org.hibernate.cache.internal.StandardQueryCache; timestamp5872026465492992
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2
value: [5872026465492992, 1]JdbcTransaction - committed JDBC Connection------------------------------------------------------------QueryCacheTest - Check get entity is cachedJdbcTransaction - committed JDBC Connection------------------------------------------------------------QueryCacheTest - Check query is cachedStandardQueryCache - Checking cached query results in region: org.hibernate.cache.internal.StandardQueryCache
StandardQueryCache - Checking query spaces are up-to-date: [Post]EhcacheGeneralDataRegion - key: Post
UpdateTimestampsCache - [Post] last update timestamp: 5872026465406976, result set timestamp: 5872026465492992
StandardQueryCache - Returning cached query resultsJdbcTransaction - committed JDBC Connection 清除所有缓存区域以确保缓存为空 运行后查询后查询缓存将检查以前存储的结果 因为没有缓存条目所以查询转到数据库 所选实体和查询结果均被缓存 然后我们验证Post实体是否存储在二级缓存中 后续查询请求将从缓存中解决而无需访问数据库 查询参数 查询参数嵌入在缓存条目键中如以下示例所示。 基本类型 首先我们将使用基本的类型过滤 private ListPost getLatestPostsByAuthorId(Session session) {return (ListPost) session.createQuery(select p from Post p join p.author a where a.id :authorId order by p.createdOn desc).setParameter(authorId, 1L).setMaxResults(10).setCacheable(true).list();
}doInTransaction(session - {LOGGER.info(Query cache with basic type parameter);ListPost posts getLatestPostsByAuthorId(session);assertEquals(1, posts.size());
}); 查询缓存条目如下所示 EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ inner joinAuthor querycache1_ on querycache0_.author_idquerycache1_.id wherequerycache1_.id? order byquerycache0_.created_on desc;parameters: ; named parameters: {authorId1}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2
value: [5871781092679680, 1] 该参数存储在高速缓存条目键中。 缓存条目值的第一个元素始终是结果集的获取时间戳。 以下元素是此查询返回的实体标识符。 实体类型 我们还可以使用实体类型作为查询参数 private ListPost getLatestPostsByAuthor(Session session) {Author author (Author) session.get(Author.class, 1L);return (ListPost) session.createQuery(select p from Post p join p.author a where a :author order by p.createdOn desc).setParameter(author, author).setMaxResults(10).setCacheable(true).list();
}doInTransaction(session - {LOGGER.info(Query cache with entity type parameter);ListPost posts getLatestPostsByAuthor(session);assertEquals(1, posts.size());
}); 缓存条目与我们之前的示例相似因为Hibernate仅将实体标识符存储在缓存条目键中。 这很有意义因为Hibernate已经缓存了Author实体。 EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ inner joinAuthor querycache1_ on querycache0_.author_idquerycache1_.id wherequerycache1_.id? order byquerycache0_.created_on desc;parameters: ; named parameters: {author1}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2
value: [5871781092777984, 1]一致性 HQL / JPQL查询无效 Hibernate二级缓存偏向于强一致性而查询缓存也不例外。 与刷新一样只要关联的表空间发生更改查询缓存就可以使其条目无效。 每次我们持久/删除/更新实体时 使用该特定表的所有查询缓存条目都将失效。 doInTransaction(session - {Author author (Author) session.get(Author.class, 1L);assertEquals(1, getLatestPosts(session).size());LOGGER.info(Insert a new Post);Post newPost new Post(Hibernate Book, author);session.persist(newPost);session.flush();LOGGER.info(Query cache is invalidated);assertEquals(2, getLatestPosts(session).size());
});doInTransaction(session - {LOGGER.info(Check Query cache);assertEquals(2, getLatestPosts(session).size());
}); 该测试将添加一个新的Post 然后重新运行可缓存的查询。 运行此测试将给出以下输出 QueryCacheTest - Insert a new Postinsert
intoPost(id, author_id, created_on, name)
values(default, 1, 2015-06-06 17:29:59.909, Hibernate Book)UpdateTimestampsCache - Pre-invalidating space [Post], timestamp: 5872029941395456
EhcacheGeneralDataRegion - key: Post value: 5872029941395456QueryCacheTest - Query cache is invalidated
StandardQueryCache - Checking cached query results in region: org.hibernate.cache.internal.StandardQueryCache
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2StandardQueryCache - Checking query spaces are up-to-date: [Post]
EhcacheGeneralDataRegion - key: Post
UpdateTimestampsCache - [Post] last update timestamp: 5872029941395456, result set timestamp: 5872029695619072
StandardQueryCache - Cached query results were not up-to-dateselectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_
fromPost querycache0_
order byquerycache0_.created_on desc limit 10StandardQueryCache - Caching query results in region: org.hibernate.cache.internal.StandardQueryCache; timestamp5872029695668224
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2
value: [5872029695668224, 2, 1]JdbcTransaction - committed JDBC ConnectionUpdateTimestampsCache - Invalidating space [Post], timestamp: 5872029695680512
EhcacheGeneralDataRegion - key: Post value: 5872029695680512------------------------------------------------------------QueryCacheTest - Check Query cacheStandardQueryCache - Checking cached query results in region: org.hibernate.cache.internal.StandardQueryCache
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2StandardQueryCache - Checking query spaces are up-to-date: [Post]
EhcacheGeneralDataRegion - key: Post
UpdateTimestampsCache - [Post] last update timestamp: 5872029695680512, result set timestamp: 5872029695668224
StandardQueryCache - Cached query results were not up-to-dateselectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_
fromPost querycache0_
order byquerycache0_.created_on desc limit 10StandardQueryCache - Caching query results in region: org.hibernate.cache.internal.StandardQueryCache; timestamp5872029695705088
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2
value: [5872029695705088, 2, 1]JdbcTransaction - committed JDBC Connection 一旦Hibernate检测到Entity状态转换 它就会使受影响的查询缓存区域预先失效 不会删除查询缓存条目但会更新其关联的时间戳 查询缓存始终检查条目键时间戳如果键时间戳比结果集加载时间戳新则它会跳过读取其值。 如果当前会话重新运行此查询则结果将再次被缓存 当前数据库事务的提交和更改从会话级隔离传播到常规读取一致性 发生实际的无效并且缓存条目时间戳再次被更新 这种方法可能破坏READ COMMITTED一致性保证因为可能进行脏读 因为在提交数据库事务之前当前隔离的更改会传播到Cache。 本机查询无效 正如我前面提到 本机查询Hibernate留在黑暗中因为它可以不知道本地查询最终可能会修改其表。 在以下测试中我们将更新Author表同时检查它对当前Post Query Cache的影响 doInTransaction(session - {assertEquals(1, getLatestPosts(session).size());LOGGER.info(Execute native query);assertEquals(1, session.createSQLQuery(update Author set name \||name||\ ).executeUpdate());LOGGER.info(Check query cache is invalidated);assertEquals(1, getLatestPosts(session).size());
}); 测试生成以下输出 QueryCacheTest - Execute native queryUpdateTimestampsCache - Pre-invalidating space [Author], timestamp: 5872035446091776
EhcacheGeneralDataRegion - key: Author value: 5872035446091776
UpdateTimestampsCache - Pre-invalidating space [Post], timestamp: 5872035446091776
EhcacheGeneralDataRegion - key: Post value: 5872035446091776updateAuthor
setname ||name||QueryCacheTest - Check query cache is invalidatedStandardQueryCache - Checking cached query results in region: org.hibernate.cache.internal.StandardQueryCache
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2StandardQueryCache - Checking query spaces are up-to-date: [Post]
EhcacheGeneralDataRegion - key: Post
UpdateTimestampsCache - [Post] last update timestamp: 5872035446091776, result set timestamp: 5872035200290816
StandardQueryCache - Cached query results were not up-to-dateselectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_
fromPost querycache0_
order byquerycache0_.created_on desc limit 10StandardQueryCache - Caching query results in region: org.hibernate.cache.internal.StandardQueryCache; timestamp5872035200364544
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2
value: [5872035200364544, 1]JdbcTransaction - committed JDBC ConnectionUpdateTimestampsCache - Invalidating space [Post], timestamp: 5872035200372736
EhcacheGeneralDataRegion - key: Post value: 5872035200372736
UpdateTimestampsCache - Invalidating space [Author], timestamp: 5872035200372736
EhcacheGeneralDataRegion - key: Author value: 5872035200372736 即使仅修改了Author表 Author和Post缓存区域也都无效。 为了解决这个问题我们需要让Hibernate知道我们要更改哪些表。 本机查询缓存区域同步 Hibernate允许我们通过查询同步提示来定义查询表空间。 提供此信息时Hibernate可以使请求的缓存区域无效 doInTransaction(session - {assertEquals(1, getLatestPosts(session).size());LOGGER.info(Execute native query with synchronization);assertEquals(1, session.createSQLQuery(update Author set name \||name||\ ).addSynchronizedEntityClass(Author.class).executeUpdate());LOGGER.info(Check query cache is not invalidated);assertEquals(1, getLatestPosts(session).size());
}); 正在生成以下输出 QueryCacheTest - Execute native query with synchronizationUpdateTimestampsCache - Pre-invalidating space [Author], timestamp: 5872036893995008
EhcacheGeneralDataRegion - key: Author value: 5872036893995008updateAuthor
setname ||name||QueryCacheTest - Check query cache is not invalidatedStandardQueryCache - Checking cached query results in region: org.hibernate.cache.internal.StandardQueryCache
EhcacheGeneralDataRegion -
key: sql: selectquerycache0_.id as id1_1_,querycache0_.author_id as author_i4_1_,querycache0_.created_on as created_2_1_,querycache0_.name as name3_1_ fromPost querycache0_ order byquerycache0_.created_on desc;parameters: ; named parameters: {}; max rows: 10; transformer: org.hibernate.transform.CacheableResultTransformer110f2StandardQueryCache - Checking query spaces are up-to-date: [Post]
EhcacheGeneralDataRegion - key: Post
UpdateTimestampsCache - [Post] last update timestamp: 5872036648169472, result set timestamp: 5872036648226816
StandardQueryCache - Returning cached query resultsJdbcTransaction - committed JDBC ConnectionUpdateTimestampsCache - Invalidating space [Author], timestamp: 5872036648263680
EhcacheGeneralDataRegion - key: Author value: 5872036648263680 只有提供的表空间无效离开了邮政查询缓存不变。 可以将本机查询和查询缓存混合使用但是需要一些努力。 结论 查询缓存可以提高频繁执行的实体查询的应用程序性能但这不是免费的。 它容易受到一致性问题的影响并且如果没有适当的内存管理控制机制它很容易变得很大。 代码可在GitHub上获得 。 翻译自: https://www.javacodegeeks.com/2015/06/how-does-hibernate-query-cache-work.htmlhibernate查询缓存
