一、案例由来
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。
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