索引下推

 

 

 

 

 

 

 

 

mysql> select @@optimizer_switch\G;
*************************** 1\. row
: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on
1 row in set (0.00 sec)

 

 

切换状态：

 

 

set ="index_condition_pushdown=off";
set ="index_condition_pushdown=on";