今天乙個朋友在問mysql資料修改後什麼時候收集統計資料，我就簡單的找了一下源**，現總結如下。如有錯誤請指出，因為我只是簡單做了一下除錯。
mysql統計資料分為持久化和非持久化
我在看更改邏輯的時候，發現非持久化統計資料是直接更新的或者說是同步更新的。但是持久化統計資料應該是非同步更新的，看起來是典型的生產者消費者模型。mysql中有乙個專門的後台執行緒來負責收集統計資料如下：
mysql> select name,thread_id from performance_schema.threads where name like '%dict_stats_thread%' \g
*************************** 1. row ***************************
name: thread/innodb/dict_stats_thread
thread_id: 25
其實更改邏輯還是相當簡單基本就是兩個函式就總結了，他們是row_update_statistics_if_needed函式和dict_stats_process_entry_from_recalc_pool函式，但是我不知道有沒有漏掉的。
持久化邏輯(persistent)
if (dict_stats_is_persistent_enabled(table))
return;
}
if (ut_difftime(ut_time(), table->stats_last_recalc)
< min_recalc_interval) else
#define min_recalc_interval 10 /* seconds */if (counter > 16 + n_rows / 16 /* 6.25% */)14.6.12 configuring optimizer statistics for innodb#0 dict_stats_recalc_pool_add (table=0x7fff1805a790) at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/dict/dict0stats_bg.cc:129
#1 0x0000000001b0f4e3 in row_update_statistics_if_needed (table=0x7fff1805a790) at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/row/row0mysql.cc:1206
#2 0x0000000001b10c34 in row_insert_for_mysql_using_ins_graph (mysql_rec=0x7fff180479a0 "\375\036", prebuilt=0x7fff18098c10)
at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/row/row0mysql.cc:1831
#3 0x0000000001b10cbf in row_insert_for_mysql (mysql_rec=0x7fff180479a0 "\375\036", prebuilt=0x7fff18098c10)
at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/row/row0mysql.cc:1857
#4 0x00000000019b04dd in ha_innobase::write_row (this=0x7fff18047460, record=0x7fff180479a0 "\375\036")
at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/handler/ha_innodb.cc:7923
#5 0x0000000000f732af in handler::ha_write_row (this=0x7fff18047460, buf=0x7fff180479a0 "\375\036") at /root/mysql5.7.14/percona-server-5.7.14-7/sql/handler.cc:8228
#6 0x00000000017d1764 in write_record (thd=0x7fff18000b70, table=0x7fff18036420, info=0x7ffff0255a30, update=0x7ffff02559b0)
at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sql_insert.cc:1864
#7 0x00000000017ce909 in sql_cmd_insert::mysql_insert (this=0x7fff18006b00, thd=0x7fff18000b70, table_list=0x7fff18006570)
at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sql_insert.cc:780
#8 0x00000000017d5349 in sql_cmd_insert::execute (this=0x7fff18006b00, thd=0x7fff18000b70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sql_insert.cc:3100
#9 0x00000000015a773e in mysql_execute_command (thd=0x7fff18000b70, first_level=true) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sql_parse.cc:3719
#10 0x00000000015adcae in mysql_parse (thd=0x7fff18000b70, parser_state=0x7ffff0257600) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sql_parse.cc:5836
#11 0x00000000015a1b6d in dispatch_command (thd=0x7fff18000b70, com_data=0x7ffff0257d70, command=com_query)
at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sql_parse.cc:1447
#12 0x00000000015a099e in do_command (thd=0x7fff18000b70) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/sql_parse.cc:1010
#13 0x00000000016e28f0 in handle_connection (arg=0x68d7220) at /root/mysql5.7.14/percona-server-5.7.14-7/sql/conn_handler/connection_handler_per_thread.cc:312
#14 0x0000000001d7a514 in pfs_spawn_thread (arg=0x37fcbc0) at /root/mysql5.7.14/percona-server-5.7.14-7/storage/perfschema/pfs.cc:2188
#15 0x0000003f74807aa1 in start_thread () from /lib64/libpthread.so.0
#16 0x0000003f740e8bcd in clone () from /lib64/libc.so.6
#0 dict_stats_update (table=0x7fff1805a790, stats_upd_option=dict_stats_recalc_persistent)
at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/dict/dict0stats.cc:3052
#1 0x0000000001cd0362 in dict_stats_process_entry_from_recalc_pool () at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/dict/dict0stats_bg.cc:349
#2 0x0000000001cd05a9 in dict_stats_thread (arg=0x0) at /root/mysql5.7.14/percona-server-5.7.14-7/storage/innobase/dict/dict0stats_bg.cc:438
#3 0x0000003f74807aa1 in start_thread () from /lib64/libpthread.so.0
#4 0x0000003f740e8bcd in clone () from /lib64/libc.so.6
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