range_optimizer_max_mem_size用于限制 Query Range 模块使用的内存。 属性说明 属性描述 参数类型CAPACITY 默认值128M 取值范围[0M,+∞) 说明 从V4.3.0 版本开始取值范围由 [16M,1G] 调整为 [0M,+∞)。 是否可修改是,支持通过ALTER SYSTEM SET语句修改。
optimizer_switch系统变量中skip_scan是否打开。 Range内存限制 range_optimizer_max_mem_size系统变量配置, 设置为0,代表不限制内存; 按照官方文档解释: a = 1 or a=2 这种查询,a = 1加上OR大概使用230bytes; a = 1 and b =1 , a =1加上AND大概使用125bytes; 可以按此估算内存使用情况。
Limiting Memory Use for Range Optimization range_optimizer_max_mem_size 0:无限制 其他值:评估超过后会有报错Memory capacity of *N* bytes for 'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query. in或者or的一个值大概需要230字节! in (1,2,…,N) and in (...
For individual queries that exceed the available range optimization memory and for which the optimizer falls back to less optimal plans, increasing the range_optimizer_max_mem_size value may improve performance. 对于超出可用范围优化内存的单个查询,并且优化器返回到不太理想的计划,增加range_optimizer_max_...
'range_optimizer_max_mem_size' exceeded. Range optimization was not done for this query. 对于UPDATE和DELETE语句,如果优化器使用全表扫描并且启用了sql_safe_updates,会发生错误而不是警告,这是因为,没有索引可以被用来确定哪行需要被修改。 估算范围扫描使用的内存 ...
...大于0,则优化器在操作时发现超出指定限制后将会改变策略(如:全表扫描),同时还会给出以下警告,所以增加 range_optimizer_max_mem_size 值可能会提高性能。...Range optimization was not done for this query...虽然 MySQL优化器为我们做了很多事情,但开发过程中该主意还得注意。
the range optimizer for tables with such dependencies. */ MAYBE_KEY, /** There is a range condition that can be used on this index. The range conditions for this index in stored in the SEL_ARG tree. */ KEY_RANGE } type; SEL_ARG *root; // The root node of the tree ...
| optimizer_trace_features | greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on | | optimizer_trace_limit | 1 | | optimizer_trace_max_mem_size | 1048576 | | optimizer_trace_offset | -1 | +---+---+mysql>SETOPTIMIZER_TRACE_MAX_MEM_SIZE=1000000; mysql>EXPLAINSELE...
Range Access使用单个索引的方式来检索包含在一个或多个索引值区间内的表行的子集。它也适用于单列或复合(组合)索引... <!-- more --> 单列索引 对于...