当前位置：网站首页>Comparative analysis of the execution efficiency of MySQL 5.7 statistical table records
Comparative analysis of the execution efficiency of MySQL 5.7 statistical table records
2022-07-06 12:48:00 【wx5caecf2ed0645】
Problem description
When the statistics are recorded , I seldom pay attention to the details , I have time to analyze it for a few days , Here is my analysis process , What's wrong , Also please correct me .
[email protected]#mysql.sock : tc0112:28:09>select count(*) from test2;
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.13 sec)
[email protected]#mysql.sock : tc0112:28:11>select count(*) from test2;
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.13 sec)
[email protected]#mysql.sock : tc0112:28:13>select count(*) from test2;
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.13 sec)
[email protected]#mysql.sock : tc0112:28:14>
It has been queried three times, and the time consumption of each query is 0.13 second .
[email protected]#mysql.sock : tc0112:31:01>select count(*) from test2 use index (PRIMARY);
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.15 sec)
[email protected]#mysql.sock : tc0112:31:02>select count(*) from test2 use index (PRIMARY);
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.15 sec)
[email protected]#mysql.sock : tc0112:31:05>select count(*) from test2 use index (PRIMARY);
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.15 sec)
Used the primary key to query three times , Each query takes 0.15 second , Why there will be 0.02 What about the difference in seconds ？
The analysis process
View execution plan
Our first thought is to see if the implementation plan is the same .
[email protected]#mysql.sock : tc0112:33:34>explain select count(*) from test2;
+----+-------------+-------+------------+-------+---------------+----------------+---------+------+---------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------+-------+---------------+----------------+---------+------+---------+----------+-------------+
| 1 | SIMPLE | test2 | NULL | index | NULL | index_vote_num | 4 | NULL | 1114117 | 100.00 | Using index |
+----+-------------+-------+------------+-------+---------------+----------------+---------+------+---------+----------+-------------+
1 row in set, 1 warning (0.07 sec)
[email protected]#mysql.sock : tc0112:33:35>explain select count(*) from test2 use index (PRIMARY);
+----+-------------+-------+------------+-------+---------------+---------+---------+------+---------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-------+------------+-------+---------------+---------+---------+------+---------+----------+-------------+
| 1 | SIMPLE | test2 | NULL | index | NULL | PRIMARY | 4 | NULL | 1114117 | 100.00 | Using index |
+----+-------------+-------+------------+-------+---------------+---------+---------+------+---------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
From the execution plan shown, we can see that , Two SQL The execution plan of the statement is different , The primary key index is slow 0.02 second , What's the cause of the ？
Check the index as follows ：
[email protected]#mysql.sock : tc0112:34:27>show index from test2;
+-------+------------+----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| test2 | 0 | PRIMARY | 1 | id | A | 1054391 | NULL | NULL | | BTREE | | |
| test2 | 1 | index_name | 1 | name | A | 1055674 | NULL | NULL | | BTREE | | |
| test2 | 1 | index_vote_num | 1 | vote_num | A | 9929 | NULL | NULL | | BTREE | | |
| test2 | 1 | index_group | 1 | group_id | A | 501 | NULL | NULL | | BTREE | | |
| test2 | 1 | index_group | 2 | sdate | A | 824214 | NULL | NULL | YES | BTREE | | |
+-------+------------+----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
5 rows in set (0.00 sec)
cardinality Is the estimate of non duplicate records in the index .
Use profile See where the time difference lies
[email protected]#mysql.sock : tc0112:41:21>select count(*) from test2;
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.14 sec)
[email protected]#mysql.sock : tc0112:41:33>show profile cpu,block io for query 3;
+----------------------+----------+----------+------------+--------------+---------------+
| Status | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+----------------------+----------+----------+------------+--------------+---------------+
| starting | 0.000047 | 0.000033 | 0.000009 | 0 | 0 |
| checking permissions | 0.000005 | 0.000004 | 0.000001 | 0 | 0 |
| Opening tables | 0.000013 | 0.000010 | 0.000003 | 0 | 0 |
| init | 0.000011 | 0.000008 | 0.000003 | 0 | 0 |
| System lock | 0.000006 | 0.000005 | 0.000001 | 0 | 0 |
| optimizing | 0.000003 | 0.000003 | 0.000001 | 0 | 0 |
| statistics | 0.000010 | 0.000007 | 0.000002 | 0 | 0 |
| preparing | 0.000007 | 0.000006 | 0.000002 | 0 | 0 |
| executing | 0.000002 | 0.000001 | 0.000000 | 0 | 0 |
| Sending data | 0.133695 | 0.133527 | 0.000000 | 0 | 0 |
| end | 0.000016 | 0.000009 | 0.000000 | 0 | 0 |
| query end | 0.000009 | 0.000009 | 0.000000 | 0 | 0 |
| closing tables | 0.000008 | 0.000008 | 0.000000 | 0 | 0 |
| freeing items | 0.000017 | 0.000017 | 0.000000 | 0 | 0 |
| cleaning up | 0.000009 | 0.000009 | 0.000000 | 0 | 0 |
+----------------------+----------+----------+------------+--------------+---------------+
15 rows in set, 1 warning (0.00 sec)
[email protected]#mysql.sock : tc0112:41:27>select count(*) from test2 use index (PRIMARY);
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.15 sec)
[email protected]#mysql.sock : tc0112:41:56>show profile cpu,block io for query 4;
+----------------------+----------+----------+------------+--------------+---------------+
| Status | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+----------------------+----------+----------+------------+--------------+---------------+
| starting | 0.000052 | 0.000036 | 0.000010 | 0 | 0 |
| checking permissions | 0.000005 | 0.000003 | 0.000001 | 0 | 0 |
| Opening tables | 0.000013 | 0.000011 | 0.000004 | 0 | 0 |
| init | 0.000010 | 0.000007 | 0.000002 | 0 | 0 |
| System lock | 0.000006 | 0.000005 | 0.000001 | 0 | 0 |
| optimizing | 0.000003 | 0.000002 | 0.000001 | 0 | 0 |
| statistics | 0.000010 | 0.000008 | 0.000002 | 0 | 0 |
| preparing | 0.000008 | 0.000006 | 0.000002 | 0 | 0 |
| executing | 0.000002 | 0.000001 | 0.000000 | 0 | 0 |
| Sending data | 0.149678 | 0.149268 | 0.000191 | 0 | 0 |
| end | 0.000014 | 0.000006 | 0.000002 | 0 | 0 |
| query end | 0.000009 | 0.000007 | 0.000002 | 0 | 0 |
| closing tables | 0.000008 | 0.000006 | 0.000002 | 0 | 0 |
| freeing items | 0.000014 | 0.000011 | 0.000003 | 0 | 0 |
| cleaning up | 0.000015 | 0.000011 | 0.000003 | 0 | 0 |
+----------------------+----------+----------+------------+--------------+---------------+
15 rows in set, 1 warning (0.00 sec)
The difference is mainly in Sending data part ,Sending data Include “ collect + send out " data .
see optimizer_trace
[email protected]#mysql.sock : tc0112:45:02>set optimizer_trace='enabled=on';
Query OK, 0 rows affected (0.00 sec)
[email protected]#mysql.sock : tc0112:46:05>set optimizer_trace_max_mem_size=1000000;
Query OK, 0 rows affected (0.00 sec)
[email protected]#mysql.sock : tc0112:46:11>set end_markers_in_json=on;
Query OK, 0 rows affected (0.00 sec)
[email protected]#mysql.sock : tc0112:46:16>select count(*) from test2;
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.13 sec)
[email protected]#mysql.sock : tc0112:46:22>select * from information_schema.optimizer_trace\G
*************************** 1. row ***************************
QUERY: select count(*) from test2
TRACE: {
"steps": [
{
"join_preparation": {
"select#": 1,
"steps": [
{
"expanded_query": "/* select#1 */ select count(0) AS `count(*)` from `test2`"
}
] /* steps */
} /* join_preparation */
},
{
"join_optimization": {
"select#": 1,
"steps": [
{
"table_dependencies": [
{
"table": "`test2`",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": [
] /* depends_on_map_bits */
}
] /* table_dependencies */
},
{
"rows_estimation": [
{
"table": "`test2`",
"table_scan": {
"rows": 1114117,
"cost": 6375
} /* table_scan */
}
] /* rows_estimation */
},
{
"considered_execution_plans": [
{
"plan_prefix": [
] /* plan_prefix */,
"table": "`test2`",
"best_access_path": {
"considered_access_paths": [
{
"rows_to_scan": 1114117,
"access_type": "scan",
"resulting_rows": 1.11e6,
"cost": 229198,
"chosen": true
}
] /* considered_access_paths */
} /* best_access_path */,
"condition_filtering_pct": 100,
"rows_for_plan": 1.11e6,
"cost_for_plan": 229198,
"chosen": true
}
] /* considered_execution_plans */
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [
] /* attached_conditions_computation */,
"attached_conditions_summary": [
{
"table": "`test2`",
"attached": null
}
] /* attached_conditions_summary */
} /* attaching_conditions_to_tables */
},
{
"refine_plan": [
{
"table": "`test2`"
}
] /* refine_plan */
}
] /* steps */
} /* join_optimization */
},
{
"join_execution": {
"select#": 1,
"steps": [
] /* steps */
} /* join_execution */
}
] /* steps */
}
MISSING_BYTES_BEYOND_MAX_MEM_SIZE: 0
INSUFFICIENT_PRIVILEGES: 0
1 row in set (0.00 sec)
[email protected]#mysql.sock : tc0112:46:33>
[email protected]#mysql.sock : tc0104:49:23>select * from information_schema.optimizer_trace\G
*************************** 1. row ***************************
QUERY: select count(*) from test2 use index (PRIMARY)
TRACE: {
"steps": [
{
"join_preparation": {
"select#": 1,
"steps": [
{
"expanded_query": "/* select#1 */ select count(0) AS `count(*)` from `test2` USE INDEX (PRIMARY)"
}
] /* steps */
} /* join_preparation */
},
{
"join_optimization": {
"select#": 1,
"steps": [
{
"table_dependencies": [
{
"table": "`test2` USE INDEX (PRIMARY)",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": [
] /* depends_on_map_bits */
}
] /* table_dependencies */
},
{
"rows_estimation": [
{
"table": "`test2` USE INDEX (PRIMARY)",
"table_scan": {
"rows": 1114117,
"cost": 6375
} /* table_scan */
}
] /* rows_estimation */
},
{
"considered_execution_plans": [
{
"plan_prefix": [
] /* plan_prefix */,
"table": "`test2` USE INDEX (PRIMARY)",
"best_access_path": {
"considered_access_paths": [
{
"rows_to_scan": 1114117,
"access_type": "scan",
"resulting_rows": 1.11e6,
"cost": 229198,
"chosen": true
}
] /* considered_access_paths */
} /* best_access_path */,
"condition_filtering_pct": 100,
"rows_for_plan": 1.11e6,
"cost_for_plan": 229198,
"chosen": true
}
] /* considered_execution_plans */
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [
] /* attached_conditions_computation */,
"attached_conditions_summary": [
{
"table": "`test2` USE INDEX (PRIMARY)",
"attached": null
}
] /* attached_conditions_summary */
} /* attaching_conditions_to_tables */
},
{
"refine_plan": [
{
"table": "`test2` USE INDEX (PRIMARY)"
}
] /* refine_plan */
}
] /* steps */
} /* join_optimization */
},
{
"join_execution": {
"select#": 1,
"steps": [
] /* steps */
} /* join_execution */
}
] /* steps */
}
MISSING_BYTES_BEYOND_MAX_MEM_SIZE: 0
INSUFFICIENT_PRIVILEGES: 0
1 row in set (0.00 sec)
According to the collection of optimizer_trace Information , I didn't see the difference .
Use strace analysis
Commands used
strace -o ./xxxx.log -T -tt -f -p `pidof mysqld`
The main contents collected are as follows ：
2779 17:31:57.090832 recvfrom(19, "\3select count(*) from test2", 27, MSG_DONTWAIT, NULL, NULL) = 27 <0.000011>
2746 17:31:57.131173 <... futex resumed> ) = -1 ETIMEDOUT (Connection timed out) <1.000589>
2746 17:31:57.131221 futex(0x3176e68, FUTEX_WAKE_PRIVATE, 1) = 0 <0.000009>
2746 17:31:57.131471 futex(0x3176e94, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 388151, {1593250318, 131449000}, ffffffff <unfinished ...>
2745 17:31:57.198173 <... futex resumed> ) = -1 ETIMEDOUT (Connection timed out) <1.000774>
2745 17:31:57.198219 futex(0x420a018, FUTEX_WAKE_PRIVATE, 1) = 0 <0.000008>
2745 17:31:57.198251 futex(0x420a044, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 388233, {1593250318, 198244000}, ffffffff <unfinished ...>
2779 17:31:57.221047 sendto(19, "\1\0\0\1\1\36\0\0\2\3def\0\0\0\10count(*)\0\f?\0\25\0\0"..., 62, MSG_DONTWAIT, NULL, 0) = 62 <0.000157>
2779 17:31:57.221269 recvfrom(19, 0x57addc0, 4, MSG_DONTWAIT, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable) <0.000009>
2779 17:31:57.221303 poll([{fd=19, events=POLLIN|POLLPRI}], 1, 600000 <unfinished ...>
2779 17:32:21.413376 recvfrom(19, "\3select count(*) from test2 use "..., 47, MSG_DONTWAIT, NULL, NULL) = 47 <0.000010>
2748 17:32:21.446209 <... nanosleep resumed> NULL) = 0 <1.009241>
2748 17:32:21.446265 nanosleep({1, 0}, <unfinished ...>
2738 17:32:21.501216 <... futex resumed> ) = -1 ETIMEDOUT (Connection timed out) <1.007208>
2738 17:32:21.501262 futex(0x3177018, FUTEX_WAKE_PRIVATE, 1) = 0 <0.000008>
2738 17:32:21.501297 futex(0x3177044, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 388723, {1593250342, 501290000}, ffffffff <unfinished ...>
2737 17:32:21.523241 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510550>
2736 17:32:21.523280 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510589>
2735 17:32:21.523287 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510591>
2734 17:32:21.523292 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510593>
2733 17:32:21.523298 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510594>
2732 17:32:21.523303 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510597>
2731 17:32:21.523309 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510598>
2730 17:32:21.523314 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510600>
2729 17:32:21.523319 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510601>
2728 17:32:21.523324 <... io_getevents resumed> [], {0, 500000000}) = 0 <0.510594>
2737 17:32:21.523368 io_getevents(140091831586816, 1, 256, <unfinished ...>
2736 17:32:21.523377 io_getevents(140091831599104, 1, 256, <unfinished ...>
2735 17:32:21.523382 io_getevents(140091831611392, 1, 256, <unfinished ...>
2734 17:32:21.523385 io_getevents(140091831623680, 1, 256, <unfinished ...>
2733 17:32:21.523389 io_getevents(140091831926784, 1, 256, <unfinished ...>
2732 17:32:21.523393 io_getevents(140091831939072, 1, 256, <unfinished ...>
2731 17:32:21.523397 io_getevents(140092021788672, 1, 256, <unfinished ...>
2730 17:32:21.523401 io_getevents(140092021800960, 1, 256, <unfinished ...>
2729 17:32:21.523405 io_getevents(140091831902208, 1, 256, <unfinished ...>
2728 17:32:21.523408 io_getevents(140091831914496, 1, 256, <unfinished ...>
2779 17:32:21.563856 sendto(19, "\1\0\0\1\1\36\0\0\2\3def\0\0\0\10count(*)\0\f?\0\25\0\0"..., 62, MSG_DONTWAIT, NULL, 0) = 62 <0.000103>
2779 17:32:21.564086 recvfrom(19, 0x57addc0, 4, MSG_DONTWAIT, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable) <0.000008>
2779 17:32:21.564120 poll([{fd=19, events=POLLIN|POLLPRI}], 1, 600000 <unfinished ...>
We found that there are more steps to use the primary key query , Naturally, it's time-consuming .
Check it out. SQL The logical reading situation of
[email protected]#mysql.sock : tc0105:39:52>show status like 'innodb_buffer%';
+---------------------------------------+--------------------------------------------------+
| Variable_name | Value |
+---------------------------------------+--------------------------------------------------+
| Innodb_buffer_pool_dump_status | Dumping of buffer pool not started |
| Innodb_buffer_pool_load_status | Buffer pool(s) load completed at 200625 11:36:26 |
| Innodb_buffer_pool_resize_status | |
| Innodb_buffer_pool_pages_data | 21727 |
| Innodb_buffer_pool_bytes_data | 355975168 |
| Innodb_buffer_pool_pages_dirty | 0 |
| Innodb_buffer_pool_bytes_dirty | 0 |
| Innodb_buffer_pool_pages_flushed | 353199 |
| Innodb_buffer_pool_pages_free | 11017 |
| Innodb_buffer_pool_pages_misc | 24 |
| Innodb_buffer_pool_pages_total | 32768 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_ahead | 0 |
| Innodb_buffer_pool_read_ahead_evicted | 0 |
| Innodb_buffer_pool_read_requests | 120950072 |
| Innodb_buffer_pool_reads | 576 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 13289147 |
+---------------------------------------+--------------------------------------------------+
18 rows in set (0.00 sec)
[email protected]#mysql.sock : tc0105:39:54>select count(*) from test2;
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.13 sec)
[email protected]#mysql.sock : tc0105:39:57>show status like 'innodb_buffer%';
+---------------------------------------+--------------------------------------------------+
| Variable_name | Value |
+---------------------------------------+--------------------------------------------------+
| Innodb_buffer_pool_dump_status | Dumping of buffer pool not started |
| Innodb_buffer_pool_load_status | Buffer pool(s) load completed at 200625 11:36:26 |
| Innodb_buffer_pool_resize_status | |
| Innodb_buffer_pool_pages_data | 21727 |
| Innodb_buffer_pool_bytes_data | 355975168 |
| Innodb_buffer_pool_pages_dirty | 0 |
| Innodb_buffer_pool_bytes_dirty | 0 |
| Innodb_buffer_pool_pages_flushed | 353199 |
| Innodb_buffer_pool_pages_free | 11017 |
| Innodb_buffer_pool_pages_misc | 24 |
| Innodb_buffer_pool_pages_total | 32768 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_ahead | 0 |
| Innodb_buffer_pool_read_ahead_evicted | 0 |
| Innodb_buffer_pool_read_requests | 121076043 |
| Innodb_buffer_pool_reads | 576 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 13289147 |
+---------------------------------------+--------------------------------------------------+
18 rows in set (0.00 sec)
[email protected]#mysql.sock : tc0105:39:59>
121076043-120950072=125971
[email protected]#mysql.sock : tc0105:40:30>show status like 'innodb_buffer%';
+---------------------------------------+--------------------------------------------------+
| Variable_name | Value |
+---------------------------------------+--------------------------------------------------+
| Innodb_buffer_pool_dump_status | Dumping of buffer pool not started |
| Innodb_buffer_pool_load_status | Buffer pool(s) load completed at 200625 11:36:26 |
| Innodb_buffer_pool_resize_status | |
| Innodb_buffer_pool_pages_data | 21728 |
| Innodb_buffer_pool_bytes_data | 355991552 |
| Innodb_buffer_pool_pages_dirty | 0 |
| Innodb_buffer_pool_bytes_dirty | 0 |
| Innodb_buffer_pool_pages_flushed | 353303 |
| Innodb_buffer_pool_pages_free | 11016 |
| Innodb_buffer_pool_pages_misc | 24 |
| Innodb_buffer_pool_pages_total | 32768 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_ahead | 0 |
| Innodb_buffer_pool_read_ahead_evicted | 0 |
| Innodb_buffer_pool_read_requests | 121120574 |
| Innodb_buffer_pool_reads | 576 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 13289849 |
+---------------------------------------+--------------------------------------------------+
18 rows in set (0.00 sec)
[email protected]#mysql.sock : tc0105:40:31>select count(*) from test2 use index (PRIMARY);
+----------+
| count(*) |
+----------+
| 1120198 |
+----------+
1 row in set (0.15 sec)
[email protected]#mysql.sock : tc0105:40:33>show status like 'innodb_buffer%';
+---------------------------------------+--------------------------------------------------+
| Variable_name | Value |
+---------------------------------------+--------------------------------------------------+
| Innodb_buffer_pool_dump_status | Dumping of buffer pool not started |
| Innodb_buffer_pool_load_status | Buffer pool(s) load completed at 200625 11:36:26 |
| Innodb_buffer_pool_resize_status | |
| Innodb_buffer_pool_pages_data | 21728 |
| Innodb_buffer_pool_bytes_data | 355991552 |
| Innodb_buffer_pool_pages_dirty | 0 |
| Innodb_buffer_pool_bytes_dirty | 0 |
| Innodb_buffer_pool_pages_flushed | 353303 |
| Innodb_buffer_pool_pages_free | 11016 |
| Innodb_buffer_pool_pages_misc | 24 |
| Innodb_buffer_pool_pages_total | 32768 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_ahead | 0 |
| Innodb_buffer_pool_read_ahead_evicted | 0 |
| Innodb_buffer_pool_read_requests | 121251637 |
| Innodb_buffer_pool_reads | 576 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 13289849 |
+---------------------------------------+--------------------------------------------------+
18 rows in set (0.00 sec)
121251637-121120574=131063
Innodb_buffer_pool_read_requests Go to the primary key query 131063, Don't use the primary key 125971, Difference between 5092.
Summary
- The execution plan is different , and MySQL Of CBO The algorithm is about , Use optimizer_trace There's no difference , We will not continue to analyze , If other experts have a better way to share .
- The logical read difference is related to the index fields used .
- Provided here MySQL Some analysis ideas and methods of , For your reference .
边栏推荐
- It has been solved by personal practice: MySQL row size too large (> 8126) Changing some columns to TEXT or BLOB or using ROW_ FORMAT
- SVN更新后不出现红色感叹号
- 如何给Arduino项目添加音乐播放功能
- 数据库课程设计：高校教务管理系统（含代码）
- MySQL时间、时区、自动填充0的问题
- Conditional probability
- Remember an experience of ECS being blown up by passwords - closing a small black house, changing passwords, and changing ports
- GPS高程拟合抗差中误差的求取代码实现
- Unity3d makes the registration login interface and realizes the scene jump
- MySQL時間、時區、自動填充0的問題
猜你喜欢
Prove the time complexity of heap sorting
Redis based distributed ID generator
NRF24L01故障排查
Matlab读取GNSS 观测值o文件代码示例
單片機藍牙無線燒錄
Mysql database index
Fairygui character status Popup
JS Title: input array, exchange the largest with the first element, exchange the smallest with the last element, and output array.
（五）R语言入门生物信息学——ORF和序列分析
Fabrication d'un sac à dos simple fairygui
随机推荐
FairyGUI簡單背包的制作
[leetcode622] design circular queue
341. Flatten nested list iterator
Special palindromes of daily practice of Blue Bridge Cup
(the first set of course design) sub task 1-5 317 (100 points) (dijkstra: heavy edge self loop)
[offer78]合并多个有序链表
Postman 中级使用教程【环境变量、测试脚本、断言、接口文档等】
关于Gateway中使用@Controller的问题
NRF24L01故障排查
Unity场景跳转及退出
idea问题记录
By v$rman_ backup_ job_ Oracle "bug" caused by details
（五）R语言入门生物信息学——ORF和序列分析
Gateway 根据服务名路由失败，报错 Service Unavailable, status=503
JS function promotion and declaration promotion of VaR variable
Mixed use of fairygui button dynamics
Flink late data processing (3)
Meanings and differences of PV, UV, IP, VV, CV
单片机蓝牙无线烧录
NovAtel 板卡OEM617D配置步骤记录