125 lines
2.5 KiB
Markdown
125 lines
2.5 KiB
Markdown
# MySQL 慢查询分析
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---
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## 查看慢查询配置
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```sql
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SHOW VARIABLES LIKE 'slow_query%';
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SHOW VARIABLES LIKE 'long_query_time';
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```
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---
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## 查询慢日志（RDS/MySQL）
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```sql
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-- 最近24小时慢查询
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SELECT
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db,
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LEFT(REPLACE(REPLACE(sql_text, '\n', ' '), ' ', ' '), 200) as sql_preview,
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query_time,
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rows_examined,
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rows_sent,
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start_time
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FROM mysql.slow_log
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WHERE start_time > DATE_SUB(NOW(), INTERVAL 24 HOUR)
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ORDER BY query_time DESC
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LIMIT 30;
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-- 查询所有慢记录
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SELECT * FROM mysql.slow_log ORDER BY start_time DESC LIMIT 20;
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```
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---
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## 查看当前运行的长查询
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```sql
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-- 查看所有查询
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SHOW FULL PROCESSLIST;
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-- 筛选长查询（超过10秒）
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SELECT
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id, User, Host, db, Time, State,
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LEFT(Info, 150) as sql_preview
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FROM information_schema.processlist
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WHERE Command = 'Query' AND Time > 10
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ORDER BY Time DESC;
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```
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---
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## 终止查询
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```sql
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-- 单个终止
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KILL <process_id>;
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-- 批量生成终止语句（按来源IP）
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SELECT CONCAT('KILL ', id, ';')
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FROM information_schema.processlist
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WHERE Host LIKE '39.99.243.191%' AND Command = 'Query';
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```
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---
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## performance_schema 分析
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```sql
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-- 按总耗时排序
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SELECT
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SCHEMA_NAME,
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LEFT(DIGEST_TEXT, 150) as sql_pattern,
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COUNT_STAR as exec_count,
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ROUND(SUM_TIMER_WAIT/1000000000000, 2) as total_sec,
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ROUND(AVG_TIMER_WAIT/1000000000, 2) as avg_ms,
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ROUND(MAX_TIMER_WAIT/1000000000000, 2) as max_sec
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FROM performance_schema.events_statements_summary_by_digest
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WHERE SCHEMA_NAME IS NOT NULL
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ORDER BY SUM_TIMER_WAIT DESC
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LIMIT 20;
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-- 按平均耗时排序
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SELECT
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SCHEMA_NAME,
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LEFT(DIGEST_TEXT, 150) as sql_pattern,
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COUNT_STAR as exec_count,
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ROUND(AVG_TIMER_WAIT/1000000000, 2) as avg_ms,
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ROUND(MAX_TIMER_WAIT/1000000000000, 2) as max_sec
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FROM performance_schema.events_statements_summary_by_digest
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WHERE SCHEMA_NAME IS NOT NULL
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ORDER BY AVG_TIMER_WAIT DESC
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LIMIT 15;
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```
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---
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## 查看表大小
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```sql
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SELECT
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table_schema,
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table_name,
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ROUND(data_length/1024/1024, 2) as data_MB,
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ROUND(index_length/1024/1024, 2) as index_MB,
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table_rows
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FROM information_schema.tables
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WHERE table_schema IN ('db1', 'db2')
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ORDER BY data_length DESC
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LIMIT 30;
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```
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---
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## 常用连接
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| 库 | 连接命令 |
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|----|----------|
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| suke 生产库（阿里云RDS） | `mysql -hrm-8vbrd2wil14hclop3vm.mysql.zhangbei.rds.aliyuncs.com -uroot -pWFFGwffg233` |
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| 二号机 | `mysql -h47.92.117.13 -uroot -px251119!` |
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---
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*创建时间：2026-03-04*
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