Using index condition是MySQL 5.6中引入的一种新特性,叫做Index Condition Pushdown(ICP),是一种在存储引擎层使用索引过滤数据的一种优化方式。这里的“下推” 是指将原来在server层进行的table filter中可以进行index filter的部分,在引擎层面使用index filter进行处理,不再需要回表进行
1.测试联合索引的最左原则的时候, 发现了5.6版本后的新特性Index Condition Pushdown 2.含义就是存储引擎层根据索引尽可能的过滤数据,然后在返回给服务器层根据where其他条件进行过滤 3.比如我有这样的联合索引 KEY `name_gid_age_index` (`name`,`gid`,`age`) , 查询的时候where name='taoshihan' and age...
MySQL执行计划中的Extra中信息非常多,不仅仅包括Using index,Using where Using index,Using index condition,Using where,尤其是在多表连接的时候,这一点在相对MSSQL来说,不够直观或者结构化。 MSSQL中是通过区分索引查找(index seek),索引扫描(index scan),表扫描(table scan)来实现具体的查询的,这图形化的执行...
Bug #41136 ORDER BY + range access:EXPLAIN shows "Using MRR" while MRR is actually not used Submitted: 30 Nov 2008 14:32Modified: 23 Nov 2010 3:34 Reporter: Sergey Petrunya Email Updates: Status: Closed Impact on me: None Category: MySQL Server: OptimizerSeverity: S3 (Non-critical)...
Taguchi L27 orthogonal array is used to model the turning process and analyze the factors (cutting speed, depth of cut and feed rate) on material removal rate, MRR, surface roughness, SR and circularity error, CE. Further, attempts are made to optimize the sustainability index taken into ...
Otherwise, the gain of using a dynamic index is: Indexing time is a little faster if the index is smaller. The join process will return only the rows fulfilling the where clause. Because the table is read sequentially when reconstructing the index there no need for MRR. Constructing the...
alternatives":[{"index":"PRIMARY","ranges":["b <= id <= c"]/* ranges */,"index_dives_for_eq_ranges":true,"rowid_ordered":true,"using_mrr":false,"index_only":false,"rows":2,"cost":2.41,"chosen":true}]/* range_scan_alternatives */,"analyzing_roworder_intersect":{"usable":...
Bug #42991 invalid memory access and/or crash when using index condition pushdown + innodb Submitted: 18 Feb 2009 19:59Modified: 14 May 2011 1:43 Reporter: Shane Bester (Platinum Quality Contributor) Email Updates: Status: Closed Impact on me: None Category: MySQL Server: OptimizerSeverity...
(blue), and single-pixel µ-TRMRR (red) techniques. TRPL (InSb), TMR, and μ-TRMRR agree well, but as shown, when using a less sensitive detector (such as MCT), the TRPL signal falls beneath the noise floor before the low-injection condition is satisfied, preventing an accurate ...
在 select 语句中...---+ 1 row in set, 1 warning (0.00 sec) 说明3:虽然 id 和 trade_no 都出现or连接的语句...说明2:在使用select * 作为查询条件是,Extra字段显示是Using index condition; Using MRR,即查找使用了索引,但是需要回表查询索引以外的字段数据。 ...说明3:在使用的搜索字段整好是组合...