慢查日志的监控及分析
慢查日志的监控及分析
- 1 检查慢查日志是否开启
- 2 MySQL 慢查日志的存储格式
- 3 MySQL 慢查日志分析工具(pt-query-digest)
-
- 3.1 安装 pt-query-digest 工具
- 3.2 查看服务器信息
- 3.3 查看磁盘开销使用信息
- 3.4 查看 MySQL 数据库信息
- 3.5 分析慢查询日志
- 3.6 查看 MySQL 的死锁信息
- 3.7 从慢查询日志中分析索引使用情况
- 3.8 查找数据库表中重复的索引
- 3.9 查看不同 MySQL 配置文件的差异
- 3.10 获取慢日志分析报告
- 4 如何通过慢查日志发现有问题的 SQL
-
- 4.1 查询次数多且每次查询占用时间长的 SQL
- 4.2 IO 大的 SQL
- 4.3 未命中的索引的 SQL
1 检查慢查日志是否开启
show variables like 'slow_query_log';
show variables like 'log_qyeries_not_using_indexes';
# 检查查询结果的value值是OFF还是ON,如果为OFF则通过下面的命令修改值
set global slow_query_log=on;
set global log_queries_not_using_indexes=on;
# 检查慢日志的位置信息
show variables like 'slow_query_log_file';
# 然后监控查询出来的日志文件
2 MySQL 慢查日志的存储格式
# SQL执行时间
SET timestamp=1689228091;
# SQL的执行内容
SELECT ORG_ID,ROUTE_ID,COUNT(*) VEH_COUNT FROM (SELECT ORG_ID,ROUTE_ID,PLATE FROM TD_BUS_ARRANGES WHERE PLATE IN (SELECT * FROM TN_BUS_VEH_COUNTER_INS) GROUP BY ORG_ID,ROUTE_ID,PLATE) A GROUP BY ORG_ID,ROUTE_ID;
# 查询的执行时间
Time: 2023-07-13T06:01:31.655194Z
# 执行SQL的主机信息
User@Host: root[root] @ [192.168.130.79] Id: 9
# SQL的查询耗时
Query_time: 40.626665
# SQL锁定时间
Lock_time: 0.000061
# 所发送的行数
Rows_sent: 0
# 锁扫描的行数
Rows_examined: 2002971
3 MySQL 慢查日志分析工具(pt-query-digest)
3.1 安装 pt-query-digest 工具
yum install wget
wget https://www.percona.com/downloads/percona-toolkit/2.2.16/RPM/percona-toolkit-2.2.16-1.noarch.rpm
yum localinstall -y percona-toolkit-2.2.16-1.noarch.rpm
# 如果出现complete，则成功安装。
wget http://percona.com/get/pt-summary
3.2 查看服务器信息
[root@localhost ~]# pt-summary
# Percona Toolkit System Summary Report ######################
Date | 2023-07-21 08:33:47 UTC (local TZ: CST +0800)
Hostname | localhost.localdomain
Uptime | 8 days, 2:30, 2 users, load average: 0.93, 0.98, 1.03
System | VMware, Inc.; VMware Virtual Platform; vNone (Other)
Service Tag | VMware-56 4d 30 99 c8 b7 54 9a-e1 0e 02 65 ce ac 0f df
Platform | Linux
Release | CentOS Linux release 7.9.2009 (Core)
Kernel | 3.10.0-1160.el7.x86_64
Architecture | CPU = 64-bit, OS = 64-bit
Threading | NPTL 2.17
SELinux | Permissive
Virtualized | VMWare
# Processor ##################################################
Processors | physical = 16, cores = 16, virtual = 16, hyperthreading = no
Speeds | 16x2399.998
Models | 16xIntel(R) Xeon(R) CPU E5-2640 v4 @ 2.40GHz
Caches | 16x25600 KB
# Memory #####################################################
Total | 31.3G
Free | 517.5M
Used | physical = 3.2G, swap allocated = 15.7G, swap used = 23.9M, virtual = 3.3G
Buffers | 27.5G
Caches | 27.6G
Dirty | 800 kB
UsedRSS | 2.3G
Swappiness | 30
DirtyPolicy | 30, 10
DirtyStatus | 0, 0
Locator Size Speed Form Factor Type Type Detail
========= ======== ================= ============= ============= ===========
RAM slot #0 16384 MB Unknown DIMM DRAM EDO
RAM slot #1 16384 MB Unknown DIMM DRAM EDO
# Mounted Filesystems ########################################
Filesystem Size Used Type Opts Mountpoint
/dev/mapper/centos-home 957G 29% xfs rw,relatime,seclabel,attr2,inode64,noquota /home
/dev/mapper/centos-root 50G 26% xfs rw,relatime,seclabel,attr2,inode64,noquota /
/dev/sda1 1014M 15% xfs rw,relatime,seclabel,attr2,inode64,noquota /boot
# Disk Schedulers And Queue Size #############################
dm-0 | 128
dm-1 | 128
dm-2 | 128
sda | [deadline] 128
sr0 | [deadline] 128
# Disk Partioning ############################################
Device Type Start End Size
============ ==== ========== ========== ==================
/dev/dm-0 Disk 53687091200
/dev/dm-1 Disk 16911433728
/dev/dm-2 Disk 1027830972416
/dev/sda Disk 1099511627776
/dev/sda1 Part 2048 2099199 1073741312
/dev/sda2 Part 2099200 2147483647 1098436836864
/dev/sr0 Disk 4712300544
/dev/sr0p1 Part 0 9203711 18849200128
/dev/sr0p2 Part 2428 20027 36042752
# Kernel Inode State #########################################
dentry-state | 46456 25932 45 0 5743 0
file-nr | 2048 0 3138874
inode-nr | 45165 7180
# LVM Volumes ################################################
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
home centos -wi-ao---- 957.24g
root centos -wi-ao---- 50.00g
swap centos -wi-ao---- 15.75g
# LVM Volume Groups ##########################################
VG VSize VFree
centos <1023.00g 4.00m
# RAID Controller ############################################
Controller | No RAID controller detected
# Network Config #############################################
Controller | VMware VMXNET3 Ethernet Controller (rev 01)
FIN Timeout | 60
Port Range | 60999
# Interface Statistics #######################################
interface rx_bytes rx_packets rx_errors tx_bytes tx_packets tx_errors
========= ========= ========== ========== ========== ========== ==========
lo 45000 500 0 45000 500 0
ens192 100000000000 300000000 0 700000000000 300000000 0
docker0 500000000000 200000000 0 70000000000 175000000 0
br-d68411005b14 0 0 0 0 0 0
# Network Devices ############################################
Device Speed Duplex
========= ========= =========
br-d68411005b14
docker0
ens192 10000Mb/s Full
# Network Connections ########################################
Connections from remote IP addresses
192.168.9.1 70
192.168.9.3 70
192.168.9.5 60
192.168.9.7 125
192.168.9.9 6
192.168.10.158 4
192.168.130.1 3
192.168.130.78 5
192.168.130.79 35
Connections to local IP addresses
192.168.130.100 400
Connections to top 10 local ports
22 2
3308 350
States of connections
ESTABLISHED 400
LISTEN 5
# Top Processes ##############################################
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
7583 mysql 20 0 9066304 2.0g 12244 S 50.0 6.6 626:21.40 mysqld
1 root 20 0 193976 6256 4200 S 0.0 0.0 2:05.02 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.18 kthreadd
4 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:+
5 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kworker/u3+
6 root 20 0 0 0 0 S 0.0 0.0 0:00.15 ksoftirqd/0
7 root rt 0 0 0 0 S 0.0 0.0 0:00.80 migration/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh
9 root 20 0 0 0 0 S 0.0 0.0 0:26.88 rcu_sched
# Notable Processes ##########################################
PID OOM COMMAND
1329 -17 sshd
# Simplified and fuzzy rounded vmstat (wait please) ##########
procs ---swap-- -----io---- ---system---- --------cpu--------
r b si so bi bo ir cs us sy il wa st
4 0 0 0 6 250 0 3 4 0 90 6 0
0 1 0 0 0 5000 8000 5000 4 2 89 5 0
0 1 0 0 0 4500 3500 1500 6 0 90 4 0
1 0 0 0 0 5000 1750 600 3 0 92 5 0
0 0 0 0 0 4000 1000 500 2 0 95 3 0
# The End ####################################################
3.3 查看磁盘开销使用信息
pt-diskstats
3.4 查看 MySQL 数据库信息
pt-mysql-summary --user=root --password=123456
mysql: [Warning] Using a password on the command line interface can be insecure.
# Percona Toolkit MySQL Summary Report #######################
System time | 2023-07-21 08:38:35 UTC (local TZ: CST +0800)
# Instances ##################################################
Port Data Directory Nice OOM Socket
===== ========================== ==== === ======
0 0
# MySQL Executable ###########################################
Path to executable | /usr/sbin/mysqld
Has symbols | Yes
# Report On Port 3308 ########################################
User | root@localhost
Time | 2023-07-21 16:38:34 (CST)
Hostname | localhost.localdomain
Version | 5.7.43 MySQL Community Server (GPL)
Built On | Linux x86_64
Started | 2023-07-19 11:08 (up 2+05:30:09)
Databases | 14
Datadir | /var/lib/mysql/
Processes | 350 connected, 1 running
Replication | Is not a slave, has 0 slaves connected
Pidfile | /var/run/mysqld/mysqld.pid (exists)
# Processlist ################################################
Command COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
Query 1 1 0 0
Sleep 350 0 350000 8000
User COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
root 350 1 0 0
Host COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
192.168.10.158 2 0 0 0
192.168.130.1 3 0 0 0
192.168.130.78 4 0 0 0
192.168.130.79 35 0 0 0
192.168.9.1 70 0 0 0
192.168.9.3 70 0 0 0
192.168.9.5 60 0 0 0
192.168.9.7 125 0 0 0
192.168.9.9 6 0 0 0
localhost 2 1 0 0
db COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
cbmv2 4 0 0 0
datac-nacos 2 0 0 0
dolphinscheduler 45 0 0 0
giot 2 0 0 0
liaocheng_gj 300 0 0 0
usercenter 2 0 0 0
State COUNT(*) Working SUM(Time) MAX(Time)
------------------------------ -------- ------- --------- ---------
350 0 0 0
starting 1 1 0 0
# Status Counters (Wait 10 Seconds) ##########################
Variable Per day Per second 11 secs
Aborted_clients 40
Aborted_connects 800
Bytes_received 10000000000 125000 90000
Bytes_sent 80000000000 900000 700000
Com_admin_commands 125000 1 1
Com_alter_table 20
Com_change_db 45
Com_commit 350000 3 1
Com_create_table 3
Com_delete 3000
Com_drop_table 2
Com_insert 20000000 225 175
Com_insert_select 10
Com_kill 15
Com_rollback 150
Com_select 7000000 80 15
Com_set_option 800000 9 4
Com_show_create_table 8
Com_show_databases 5
Com_show_fields 7
Com_show_status 20
Com_show_table_status 15
Com_show_tables 3
Com_show_variables 4
Com_show_warnings 225
Com_update 3500000 40
Com_update_multi 150
Connections 15000 1
Created_tmp_disk_tables 350 1
Created_tmp_files 12500
Created_tmp_tables 90000 1 6
Handler_commit 20000000 225 60
Handler_delete 10000000 125
Handler_external_lock 50000000 600 350
Handler_read_first 2500000 30 3
Handler_read_key 350000000 4000 1750
Handler_read_last 125
Handler_read_next 4000000000 50000 30000
Handler_read_prev 300000 3
Handler_read_rnd 17500000 200 20
Handler_read_rnd_next 3000000000 35000 20000
Handler_rollback 70
Handler_update 300000000 3500 1750
Handler_write 50000000 600 300
Innodb_buffer_pool_bytes_data 50000000 600 1250000
Innodb_buffer_pool_bytes_dirty 7000000 80 -755153
Innodb_buffer_pool_pages_flushed 8000000 90 100
Innodb_buffer_pool_read_ahead 5000000 60 60
Innodb_buffer_pool_read_ahead_evicted 45000
Innodb_buffer_pool_read_requests 9000000000 100000 100000
Innodb_buffer_pool_reads 30000000 350 1000
Innodb_buffer_pool_wait_free 200000 2
Innodb_buffer_pool_write_requests 250000000 3000 700
Innodb_data_fsyncs 1250000 15 15
Innodb_data_read 600000000000 7000000 17500000
Innodb_data_reads 40000000 450 1000
Innodb_data_writes 9000000 100 100
Innodb_data_written 300000000000 3000000 3500000
Innodb_dblwr_pages_written 8000000 90 100
Innodb_dblwr_writes 175000 2 2
Innodb_log_write_requests 30000000 350 80
Innodb_log_writes 600000 7 5
Innodb_os_log_fsyncs 600000 7 6
Innodb_os_log_written 12500000000 150000 45000
Innodb_pages_created 300000 3 1
Innodb_pages_read 40000000 450 1000
Innodb_pages_written 8000000 90 100
Innodb_row_lock_time 12500
Innodb_row_lock_waits 175
Innodb_rows_deleted 10000000 125
Innodb_rows_inserted 22500000 250 70
Innodb_rows_read 7000000000 90000 50000
Innodb_rows_updated 9000000 100 60
Innodb_num_open_files 150
Innodb_available_undo_logs 60
Key_read_requests 25
Key_reads 6
Open_table_definitions 225
Opened_files 15000
Opened_table_definitions 250
Opened_tables 60000
Qcache_not_cached 7000000 80 15
Queries 30000000 350 200
Questions 30000000 350 200
Select_full_join 9000
Select_range 5000
Select_scan 2500000 30 3
Slow_queries 8000 1
Sort_merge_passes 7000
Sort_range 15000
Sort_rows 17500000 225 20
Sort_scan 150000 1 1
Ssl_accepts 450
Ssl_finished_accepts 45
Ssl_session_cache_misses 6
Ssl_used_session_cache_entries 40
Table_locks_immediate 6000000 70 100
Table_locks_waited 15
Table_open_cache_hits 25000000 300 175
Table_open_cache_misses 60000
Table_open_cache_overflows 60000
Threads_created 175
Uptime 90000 1 1
# Table cache ################################################
Size | 400
Usage | 100%
# Key Percona Server features ################################
Table & Index Stats | Not Supported
Multiple I/O Threads | Enabled
Corruption Resilient | Not Supported
Durable Replication | Not Supported
Import InnoDB Tables | Not Supported
Fast Server Restarts | Not Supported
Enhanced Logging | Not Supported
Replica Perf Logging | Disabled
Response Time Hist. | Not Supported
Smooth Flushing | Not Supported
HandlerSocket NoSQL | Not Supported
Fast Hash UDFs | Unknown
# Percona XtraDB Cluster #####################################
# Plugins ####################################################
InnoDB compression | ACTIVE
# Query cache ################################################
query_cache_type | OFF
Size | 1.0M
Usage | 1%
HitToInsertRatio | 0%
# Schema #####################################################
Specify --databases or --all-databases to dump and summarize schemas
# Noteworthy Technologies ####################################
SSL | Yes
Explicit LOCK TABLES | No
Delayed Insert | No
XA Transactions | No
NDB Cluster | No
Prepared Statements | No
Prepared statement count | 0
# InnoDB #####################################################
Version | 5.7.43
Buffer Pool Size | 128.0M
Buffer Pool Fill | 90%
Buffer Pool Dirty | 10%
File Per Table | ON
Page Size | 16k
Log File Size | 2 * 48.0M = 96.0M
Log Buffer Size | 16M
Flush Method |
Flush Log At Commit | 1
XA Support | ON
Checksums | ON
Doublewrite | ON
R/W I/O Threads | 4 4
I/O Capacity | 200
Thread Concurrency | 0
Concurrency Tickets | 5000
Commit Concurrency | 0
Txn Isolation Level | REPEATABLE-READ
Adaptive Flushing | ON
Adaptive Checkpoint |
Checkpoint Age | 2M
InnoDB Queue | 0 queries inside InnoDB, 0 queries in queue
Oldest Transaction | 0 Seconds
History List Len | 80
Read Views | 0
Undo Log Entries | 0 transactions, 0 total undo, 0 max undo
Pending I/O Reads | 0 buf pool reads, 0 normal AIO, 0 ibuf AIO, 0 preads
Pending I/O Writes | 0 buf pool (0 LRU, 0 flush list, 0 page); 0 AIO, 0 sync, 0 log IO (0 log, 0 chkp); 0 pwrites
Pending I/O Flushes | 1 buf pool, 0 log
Transaction States | 109xnot started
# MyISAM #####################################################
Key Cache | 8.0M
Pct Used | 20%
Unflushed | 0%
# Security ###################################################
Users |
Old Passwords | 0
# Binary Logging #############################################
# Noteworthy Variables #######################################
Auto-Inc Incr/Offset | 1/1
default_storage_engine | InnoDB
flush_time | 0
init_connect |
init_file |
sql_mode | STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
join_buffer_size | 256k
sort_buffer_size | 256k
read_buffer_size | 128k
read_rnd_buffer_size | 256k
bulk_insert_buffer | 0.00
max_heap_table_size | 16M
tmp_table_size | 16M
max_allowed_packet | 4M
thread_stack | 256k
log |
log_error | /var/log/mysqld.log
log_warnings | 2
log_slow_queries |
log_queries_not_using_indexes | ON
log_slave_updates | OFF
# Configuration File #########################################
Config File | /etc/my.cnf
[mysqld]
default-storage-engine = INNODB
character_set_server = utf8
port = 3308
lower_case_table_names = 1
max_connections = 5000
sql-mode = STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
datadir = /var/lib/mysql
socket = /var/lib/mysql/mysql.sock
symbolic-links = 0
log-error = /var/log/mysqld.log
pid-file = /var/run/mysqld/mysqld.pid
# The End ####################################################
3.5 分析慢查询日志
pt-query-digest /var/lib/mysql/localhost-slow.log
# 28.7s user time, 180ms system time, 66.66M rss, 261.23M vsz
# Current date: Fri Jul 21 17:36:35 2023
# Hostname: localhost.localdomain
# Files: /var/lib/mysql/localhost-slow.log
# Overall: 181.92k total, 135 unique, 0 QPS, 0x concurrency ______________
# Attribute total min max avg 95% stddev median
# ============ ======= ======= ======= ======= ======= ======= =======
# Exec time 2310s 51us 33s 13ms 287us 269ms 60us
# Lock time 31s 22us 1s 167us 84us 8ms 25us
# Rows sent 34.61M 0 2.19M 199.50 0 5.73k 0
# Rows examine 301.56M 0 2.27M 1.70k 13.83 22.42k 0
# Query size 31.24M 24 1.80M 180.06 158.58 4.25k 158.58
# Profile
# Rank Query ID Response time Calls R/Call V/M Item
# ==== ================== ============== ====== ======= ===== ============
# 1 0xF4787368A611D689 494.0212 21.4% 1041 0.4746 0.65 SELECT TD_GPS_BUS_HIS
# 2 0x80FFA60035A8F04E 304.3970 13.2% 58 5.2482 2.13 SELECT V?_OPERATIONAL_KILOMETRE V?_SHIFT_ANALYSIS V?_OPERATIONAL_KILOMETRE v?_shift_analysis td_bus_payment_detail
# 3 0x2A7DDE54305082AB 168.4274 7.3% 6 28.0712 1.13 DELETE v?_basic_shift
# 4 0x19678C5E87785D2B 159.8534 6.9% 31 5.1566 3.22 SELECT V?_SHIFT_ANALYSIS
# 5 0x4D5491F4C8E1BD0B 148.9508 6.4% 10 14.8951 0.90 SELECT td_station_add_up_volume_?_sec
# 6 0x8768BFB3856D30BA 120.3152 5.2% 3714 0.0324 0.19 SELECT t_ds_command t_ds_process_definition
# 7 0x8099F96A26863B76 113.9403 4.9% 771 0.1478 0.16 SELECT TD_BUS_PAYMENT_DETAIL
# 8 0xD2EC827E4938634E 107.4045 4.6% 257 0.4179 0.52 SELECT TD_BUS_PAYMENT_DETAIL
# 9 0xEA432256AC539465 50.6545 2.2% 4 12.6636 0.51 SELECT V?_BASIC_DRIVER
# 10 0xB52F563B59470B6A 48.6646 2.1% 170872 0.0003 0.22 SELECT TC_HOLIDAY
# 11 0xD2562A1E022249E4 46.4792 2.0% 257 0.1809 0.16 SELECT TD_BUS_PAYMENT_DETAIL
# 12 0x76C32E6F877CB100 42.8575 1.9% 766 0.0559 0.15 SELECT t_ds_worker_group
# 13 0x226F3864AFE8A3F9 39.0383 1.7% 763 0.0512 0.18 SELECT t_ds_alert
# 14 0xAF0D58FA9654C2F1 35.0482 1.5% 3 11.6827 0.07 SELECT v?_shift_analysis
# 15 0xF413B276033F1D9E 30.9013 1.3% 257 0.1202 0.23 SELECT TD_BUS_PAYMENT_DETAIL
# 16 0xCBD02E4AB231392C 30.6546 1.3% 257 0.1193 0.24 SELECT TD_BUS_PAYMENT_DETAIL tn_bus_stop_area_copy tn_bus_stop_area
# 17 0xEB1B0E22AF922FCA 29.0864 1.3% 32 0.9089 1.28 SELECT UNION V?_PASSENGER_FLOW
3.6 查看 MySQL 的死锁信息
pt-deadlock-logger --user=root --password=123456 --host=localhost
3.7 从慢查询日志中分析索引使用情况
pt-index-usage --user=root --password=123456 /var/lib/mysql/localhost-slow.log
# 这个命令会显示出那些 SQL 没有命中索引，那些索引没有被使用过等等。
ALTER TABLE `cbmv2`.`wp_material_stock` DROP KEY `ware_code_index`; -- type:non-unique
ALTER TABLE `giot`.`sys_resource` DROP KEY `idx_create_date`, DROP KEY `idx_resource_code`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`sys_dict_data` DROP KEY `idx_sort`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`td_bus_arranges` DROP KEY `LEAVE_ARRIVE_INDEX`, DROP KEY `LEAVE_TIME_INDEX`, DROP KEY `PLATE`, DROP KEY `REALARRIVETTIME`, DROP KEY `REALLEAVETIME`, DROP KEY `idx_run_date`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`td_connector_status_info` DROP KEY `index_ConnectorID`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`td_station_add_up_volume_30_sec` DROP KEY `idx_STATTIME`, DROP KEY `index_station_his`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`v3_basic_line` DROP KEY `company_id`, DROP KEY `line_id`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`v3_basic_shift` DROP KEY `ORG_ID`, DROP KEY `REALLEAVETIME`, DROP KEY `ROUTE_NAME`, DROP KEY `RUN_DATE`, DROP KEY `flag`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`v3_major_num` DROP KEY `update_date_time`; -- type:non-unique
ALTER TABLE `liaocheng_gj`.`v3_shift_analysis` DROP KEY `LEAVE_STATION_DATE`, DROP KEY `LINE_SCHEDULING_DIAGRAM`, DROP KEY `company_id`, DROP KEY `idx_leave_time`, DROP KEY `line_id`, DROP KEY `movDir`; -- type:non-unique
3.8 查找数据库表中重复的索引
pt-duplicate-key-checker --user=root --password=123456
# 这个命令会显示出数据库中那些索引是重复索引，那些索引可以进行修改。会以 SQL 的形式展示出来。
# ########################################################################
# liaocheng_gj.v3_line_hour_passenger_flow
# ########################################################################
# mult_name_hour_date is a duplicate of PRIMARY
# Key definitions:
# KEY `mult_name_hour_date` (`line_name`,`stat_date`,`hour`) USING BTREE
# PRIMARY KEY (`line_name`,`stat_date`,`hour`) USING BTREE,
# Column types:
# `line_name` varchar(40) collate utf8mb4_unicode_ci not null comment '????'
# `stat_date` date not null comment '????'
# `hour` int(11) not null comment '??'
# To remove this duplicate index, execute:
ALTER TABLE `liaocheng_gj`.`v3_line_hour_passenger_flow` DROP INDEX `mult_name_hour_date`;
3.9 查看不同 MySQL 配置文件的差异
pt-config-diff /etc/my.cnf /etc/my_master.cnf
3.10 获取慢日志分析报告
pt-query-digest --user=root --password=123456 /var/lib/mysql/localhost-slow.log > slow.report
4 如何通过慢查日志发现有问题的 SQL
4.1 查询次数多且每次查询占用时间长的 SQL
通常为pt-query-digest分析的前几个查询；该工具可以很清楚的看出每个SQL执行的次数及百分比等信息，执行的次数多，占比比较大的SQL。
4.2 IO 大的 SQL
注意pt-query-digest分析中的Rows examine项。扫描的行数越多，IO越大。
4.3 未命中的索引的 SQL
注意pt-query-digest分析中的Rows examine 和Rows Send的对比。说明该SQL的索引命中率不高，对于这种SQL，我们要重点进行关注。