最近看到有人在问如下：
其中的sending data是什么意思。隔离级别为RR，语句为insert..select。
二、关于sending data
以前就说过这个问题，实际上sending data可能包含如下：
Innodb 层数据的定位返回给MySQL 层
Innodb 层数据的查询返回给MySQL 层
Innodb 层数据的修改(如果是insert..select)
Innodb 层加锁以及等待
等待进入Innodb层(innodb_thread_concurrency参数)
MySQL 层发送数据给客户端
三、RR模式下对于insert..selcet 处于 sending data的原因总结
RR模式下insert..select的select表会上S行锁，如果这行处于X锁则会出现 sending data状态
insert..selcet中insert记录如果处于堵塞（唯一性检查）状态会处于 sending data状态
整个过程如果需要操作的数据量较大，处于sending data状态。
四、每行数据处理方式
929 T@4: | | | | | | THD::enter_stage: 'Sending data' /cdh/mysqldebug/percona-server-5.7.29-32/sql/sql_executor.cc:202
930 T@4: | | | | | | >PROFILING::status_change
931 T@4: | | | | | | <PROFILING::status_change 391
932 T@4: | | | | | | info: Sending data
933 T@4: | | | | | | >do_select
934 T@4: | | | | | | | >sub_select
935 T@4: | | | | | | | | >init_read_record
936 T@4: | | | | | | | | | info: using rr_sequential
937 T@4: | | | | | | | | | >ha_rnd_init
938 T@4: | | | | | | | | | | >change_active_index
939 T@4: | | | | | | | | | | | >innobase_get_index
940 T@4: | | | | | | | | | | | <innobase_get_index 10117
941 T@4: | | | | | | | | | | <change_active_index 10241
942 T@4: | | | | | | | | | <ha_rnd_init 3111
943 T@4: | | | | | | | | | >innobase_trx_init
944 T@4: | | | | | | | | | <innobase_trx_init 3109
945 T@4: | | | | | | | | <init_read_record 349
946 T@4: | | | | | | | | >handler::ha_rnd_next
947 T@4: | | | | | | | | | >rnd_next
948 T@4: | | | | | | | | | | >index_first
949 T@4: | | | | | | | | | | | >index_read
950 T@4: | | | | | | | | | | | | >row_search_mvcc
951 T@4: | | | | | | | | | | | | | >row_sel_store_mysql_rec
952 T@4: | | | | | | | | | | | | | | >row_sel_store_mysql_field_func
953 T@4: | | | | | | | | | | | | | | <row_sel_store_mysql_field_func 3275
954 T@4: | | | | | | | | | | | | | | >row_sel_store_mysql_field_func
955 T@4: | | | | | | | | | | | | | | <row_sel_store_mysql_field_func 3275
956 T@4: | | | | | | | | | | | | | <row_sel_store_mysql_rec 3465
957 T@4: | | | | | | | | | | | | <row_search_mvcc 6574
958 T@4: | | | | | | | | | | | <index_read 10042
959 T@4: | | | | | | | | | | <index_first 10430
960 T@4: | | | | | | | | | <rnd_next 10531
961 T@4: | | | | | | | | <handler::ha_rnd_next 3172
962 T@4: | | | | | | | | >evaluate_join_record
963 T@4: | | | | | | | | | enter: join: 0x7ffef8019970 join_tab index: 0 table: testlock cond: 0x0
964 T@4: | | | | | | | | | counts: evaluate_join_record join->examined_rows++: 1
965 T@4: | | | | | | | | | >end_send
966 T@4: | | | | | | | | | | >Query_result_insert::send_data
967 T@4: | | | | | | | | | | | >fill_record
968 T@4: | | | | | | | | | | | | >Item_field::save_in_field_inner
969 T@4: | | | | | | | | | | | | <Item_field::save_in_field_inner 6720
970 T@4: | | | | | | | | | | | | >Item_field::save_in_field_inner
971 T@4: | | | | | | | | | | | | <Item_field::save_in_field_inner 6720
972 T@4: | | | | | | | | | | | <fill_record 9801
973 T@4: | | | | | | | | | | | >write_record
974 T@4: | | | | | | | | | | | | >init_alloc_root
975 T@4: | | | | | | | | | | | | | enter: root: 0x7fffe8e48c20
976 T@4: | | | | | | | | | | | | <init_alloc_root 100
977 T@4: | | | | | | | | | | | | >COPY_INFO::set_function_defaults
978 T@4: | | | | | | | | | | | | <COPY_INFO::set_function_defaults 135
979 T@4: | | | | | | | | | | | | >handler::ha_write_row
980 T@4: | | | | | | | | | | | | | >ha_innobase::write_row
981 T@4: | | | | | | | | | | | | | | >row_ins
982 T@4: | | | | | | | | | | | | | | | row_ins: table: test/testbb
983 T@4: | | | | | | | | | | | | | | | >row_ins_index_entry_step
984 T@4: | | | | | | | | | | | | | | | | >row_ins_clust_index_entry
985 T@4: | | | | | | | | | | | | | | | | | >row_ins_clust_index_entry_low
986 T@4: | | | | | | | | | | | | | | | | | | >btr_cur_search_to_nth_level
987 T@4: | | | | | | | | | | | | | | | | | | <btr_cur_search_to_nth_level 2092
988 T@4: | | | | | | | | | | | | | | | | | | >thd_report_row_lock_wait
989 T@4: | | | | | | | | | | | | | | | | | | <thd_report_row_lock_wait 4280
990 T@4: | | | | | | | | | | | | | | | | | <row_ins_clust_index_entry_low 2692
991 T@4: | | | | | | | | | | | | | | | | <row_ins_clust_index_entry 3337
992 T@4: | | | | | | | | | | | | | | | <row_ins_index_entry_step 3619
993 T@4: | | | | | | | | | | | | | | <row_ins 3763
994 T@4: | | | | | | | | | | | | | | >thd_mark_transaction_to_rollback
995 T@4: | | | | | | | | | | | | | | <thd_mark_transaction_to_rollback 4147
996 T@4: | | | | | | | | | | | | | <ha_innobase::write_row 8895
997 T@4: | | | | | | | | | | | | <handler::ha_write_row 8565
及RR模式下insert select的逻辑大概为查询一行加锁（RC下没有加锁步骤）一行插入一行，直到所有行处理完成。整个过程处于'Sending data'状态下面。因此insert select和普通的insert操作有较大的区别。
关于sending data扩展阅读，参考我的一篇文章：
MySQL：sending data状态包含了什么
http://blog.itpub.net/7728585/viewspace-2215202/
全文完。
索引
负载高
写入慢
排查思路
分页
MySQL 8
另外，叶老师在腾讯课堂《MySQL性能优化》精编版第一期已完结，本课程讲解读几个MySQL性能优化的核心要素：合理利用索引，降低锁影响，提高事务并发度。
下面是自动拼团的二维码直接享受组团价