Using where;Using index表示查询的列被索引覆盖,且where筛选条件是索引列前导列的一个范围,或者是索引列的非前导列,例如:select id from test where id > 5;。很明显,效率也很高。 Using where表示查询的列未被索引覆盖,且where筛选条件是索引列前导列的一个范围,或者是索引列的非前导列,或者是非索引列,例...
出现Using where Using index意味着是通过索引扫描(或者表扫描)来实现sql语句执行的,即便是索引前导列的索引范围查找也有一点范围扫描的动作,不管是前非索引前导列引起的,还是非索引列查询引起的。 20200313补充,这里有一个很经典的例子,会出现using index condition;using where的情况,这种情况暂时不知道怎么去解释,...
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...
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...
Using index condition; Using where; Using temporary; Using filesort it is using idx3 which is defined as KEY `idx3` (`col2`(86)) push_index_cond() and co correctly detect that "col2 <= '6566-06-15" part of the condition cannot be checked by using the index. The "col24 <> '...
Bug #41136ORDER 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 PetrunyaEmail Updates: Status:ClosedImpact on me: None Category:MySQL Server: OptimizerSeverity:S3 (Non-critical) ...
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":...
The number of theoretical and empirical literature on Industry 4.0 research has seen tremendous growth over the past few years. We seek to identify and classify the popular research topics published on Industry 4.0 in business and economics literature us
Reporter: Olav Sandstå Email Updates: Status: Closed Impact on me: None Category: MySQL Server: OptimizerSeverity: S5 (Performance) Version: 6.0.14 (mysql-6.0-codebase)OS: Any Assigned to: Olav Sandstå CPU Architecture: Any Tags: index_condition_pushdown, optimizer_switch View...
TRMRR set-up, which consists of a microstrip SRR coupled to a microstrip busline. As the bare pixel is unintentionally doped (UID; see Methods), its dark conductivity can inadvertently short the resonator; furthermore, filling up the air gap with a larger index material capacitively loads the...