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: | | | | | | 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_trx_init
    944 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
    955 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
    971 T@4: | | | | | | | | | | | | write_record
    974 T@4: | | | | | | | | | | | | >init_alloc_root
    975 T@4: | | | | | | | | | | | | | enter: root: 0x7fffe8e48c20
    976 T@4: | | | | | | | | | | | | COPY_INFO::set_function_defaults
    978 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: | | | | | | | | | | | | | | | | | | thd_report_row_lock_wait
    989 T@4: | | | | | | | | | | | | | | | | | | thd_mark_transaction_to_rollback
    995 T@4: | | | | | | | | | | | | | |