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随笔:sending data状态包含了使用内部临时表

原创 MySQL 作者:gaopengtttt 时间:2019-11-02 22:29:50 0 删除 编辑

这是一个我的随笔记录,这些过程非常有用,也非常明显。

欢迎关注我的《深入理解MySQL主从原理 32讲 》,如下:

image.png

如果图片不能显示可查看下面链接:
https://www.jianshu.com/p/d636215d767f

语句如下:

mysql> desc select id,count(*) from t110 group by  id;
+----+-------------+-------+------------+------+---------------+------+---------+------+-------+----------+---------------------------------+
| id | select_type | table | partitions | type | possible_keys | key  | key_len | ref  | rows  | filtered | Extra                           |
+----+-------------+-------+------------+------+---------------+------+---------+------+-------+----------+---------------------------------+
|  1 | SIMPLE      | t110  | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 99395 |   100.00 | Using temporary; Using filesort |
+----+-------------+-------+------------+------+---------------+------+---------+------+-------+----------+---------------------------------+
1 row in set, 1 warning (0.00 sec)

存入内部临时表的操作也在’sending data’ 下面,下面的debug trace可以看出
操作是获取innodb层一条数据handler::ha_rnd_next,然后在内部临时表中查询
这行记录hp_search,如果存在则做相应的更改heap_update(如count累加,sum加值等)

使用内部临时表
   1249 T@3: | | | | | | | | >handler::ha_rnd_next
   1250 T@3: | | | | | | | | | >rnd_next
   1251 T@3: | | | | | | | | | | >general_fetch
   1252 T@3: | | | | | | | | | | | >row_search_mvcc
   1253 T@3: | | | | | | | | | | | | >row_sel_store_mysql_rec
   1254 T@3: | | | | | | | | | | | | | >row_sel_store_mysql_field_func
   1255 T@3: | | | | | | | | | | | | | <row_sel_store_mysql_field_func 3267
   1256 T@3: | | | | | | | | | | | | <row_sel_store_mysql_rec 3457
   1257 T@3: | | | | | | | | | | | <row_search_mvcc 6453
   1258 T@3: | | | | | | | | | | <general_fetch 9913
   1259 T@3: | | | | | | | | | <rnd_next 10086
   1260 T@3: | | | | | | | | <handler::ha_rnd_next 3159
   1261 T@3: | | | | | | | | >evaluate_join_record
   1262 T@3: | | | | | | | | | enter: join: 0x7ffe7c007778 join_tab index: 0 table: t112 cond: 0x0
   1263 T@3: | | | | | | | | | counts: evaluate_join_record join->examined_rows++: 4
   1264 T@3: | | | | | | | | | >sub_select_op
   1265 T@3: | | | | | | | | | | >end_update
   1266 T@3: | | | | | | | | | | | >handler::ha_index_read_map
   1267 T@3: | | | | | | | | | | | | >heap_rkey
   1268 T@3: | | | | | | | | | | | | | enter: info: 0x7ffe7caa74d0  inx: 0
   1269 T@3: | | | | | | | | | | | | | >hp_search
   1270 T@3: | | | | | | | | | | | | | | exit: hash: 0x105050504
   1271 T@3: | | | | | | | | | | | | | | exit: found key at 0x7ffe7ceb4880
   1272 T@3: | | | | | | | | | | | | | <hp_search 124
   1273 T@3: | | | | | | | | | | | | | >hp_extract_record
   1274 T@3: | | | | | | | | | | | | | <hp_extract_record 369
   1275 T@3: | | | | | | | | | | | | <heap_rkey 81
   1276 T@3: | | | | | | | | | | | <handler::ha_index_read_map 3261
   1277 T@3: | | | | | | | | | | | >hanlder::ha_update_row
   1278 T@3: | | | | | | | | | | | | >heap_update
   1279 T@3: | | | | | | | | | | | | | >hp_copy_record_data_to_chunks
   1280 T@3: | | | | | | | | | | | | | <hp_copy_record_data_to_chunks 308
   1281 T@3: | | | | | | | | | | | | <heap_update 79
   1282 T@3: | | | | | | | | | | | <hanlder::ha_update_row 8518
   1283 T@3: | | | | | | | | | | <end_update 3482
   1284 T@3: | | | | | | | | | <sub_select_op 1085
   1285 T@3: | | | | | | | | <evaluate_join_record 1707

下面是count(*)累加关于heap_update old值和new值的查看

Breakpoint 2, heap_update (info=0x7ffe7c9a9620, old_record=0x7ffe7c00f3b8  <incomplete sequence \375>, new_record=0x7ffe7c00f3a0  <incomplete sequence \375>)
    at /root/mysqlall/percona-server-locks-detail-5.7.22/storage/heap/hp_update.c:24
24        my_bool auto_key_changed= 0;
(gdb) x/16bx 0x7ffe7c00f3b8
0x7ffe7c00f3b8: 0xfd    0x00    0x01    0x00    0x00    0x00    0x01    0x00
0x7ffe7c00f3c0: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x00
(gdb) x/16bx 0x7ffe7c00f3a0
0x7ffe7c00f3a0: 0xfd    0x00    0x01    0x00    0x00    0x00    0x02    0x00
0x7ffe7c00f3a8: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x00
(gdb) c
Continuing.
Breakpoint 2, heap_update (info=0x7ffe7c9a9620, old_record=0x7ffe7c00f3b8  <incomplete sequence \375>, new_record=0x7ffe7c00f3a0  <incomplete sequence \375>)
    at /root/mysqlall/percona-server-locks-detail-5.7.22/storage/heap/hp_update.c:24
24        my_bool auto_key_changed= 0;
(gdb) x/16bx 0x7ffe7c00f3b8
0x7ffe7c00f3b8: 0xfd    0x00    0x01    0x00    0x00    0x00    0x02    0x00
0x7ffe7c00f3c0: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x00
(gdb) x/16bx 0x7ffe7c00f3a0
0x7ffe7c00f3a0: 0xfd    0x00    0x01    0x00    0x00    0x00    0x03    0x00
0x7ffe7c00f3a8: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x00

注意到key = 1 的这个值,第一次断点old值为0x01 new值为0x02,第二次断点old值为0x02 new值为0x03

然后遍历完所有的行过后,进入排序状态为Creating sort index

   1526 T@3: | | | | | | | | | THD::enter_stage: 'Creating sort index' /root/mysqlall/percona-server-locks-detail-5.7.22/sql/sql_executor.cc:2604
   1527 T@3: | | | | | | | | | >PROFILING::status_change
   1528 T@3: | | | | | | | | | <PROFILING::status_change 384
   1529 T@3: | | | | | | | | | >create_sort_index
   1530 T@3: | | | | | | | | | | >my_raw_malloc
   1531 T@3: | | | | | | | | | | | my: size: 376  my_flags: 48
   1532 T@3: | | | | | | | | | | | exit: ptr: 0x7ffe7c9d1a90
   1533 T@3: | | | | | | | | | | <my_raw_malloc 219
   1534 T@3: | | | | | | | | | | >heap_info
   1535 T@3: | | | | | | | | | | <heap_info 57
   1536 T@3: | | | | | | | | | | >filesort
   1537 T@3: | | | | | | | | | | | >make_sortorder
   1538 T@3: | | | | | | | | | | | | >alloc_root
   1539 T@3: | | | | | | | | | | | | | enter: root: 0x7ffe7c003c08
   1540 T@3: | | | | | | | | | | | | | exit: ptr: 0x7ffe7caa4fc8
   1541 T@3: | | | | | | | | | | | | <alloc_root 304
   1542 T@3: | | | | | | | | | | | <make_sortorder 663
   1543 T@3: | | | | | | | | | | | opt: (null): starting struct
   1544 T@3: | | | | | | | | | | | opt: filesort_information: starting struct
   1545 T@3: | | | | | | | | | | | opt: (null): starting struct
   1546 T@3: | | | | | | | | | | | opt: direction: "asc"
   1547 T@3: | | | | | | | | | | | opt: table: "intermediate_tmp_table"
   1548 T@3: | | | | | | | | | | | opt: field: "id"
   1549 T@3: | | | | | | | | | | | opt: (null): ending struct
   1550 T@3: | | | | | | | | | | | opt: filesort_information: ending struct
   1551 T@3: | | | | | | | | | | | info: sort_length: 5

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