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yashandb教程FG047-YashanDB会话与锁分析

教程整理：风哥教程  |  更新时间：2026-04-06  |  教程分类：YashanDB教程  |  文档学习：40

本文档风哥主要介绍YashanDB会话与锁分析相关知识，包括YashanDB会话概念、锁概念、锁类型、会话管理、锁管理、性能考量、会话分析、锁分析、故障排查、实战案例、最佳实践等内容，风哥教程参考YashanDB官方文档性能优化与故障处理内容编写，适合DBA人员在学习和测试中使用，如果要应用于生产环境则需要自行确认。更多视频教程www.fgedu.net.cn

Part01-基础概念与理论知识

1.1 YashanDB会话概念

YashanDB会话是指客户端与数据库服务器之间的连接，每个会话对应一个客户端连接。会话包含了客户端的连接信息、执行的SQL语句、事务状态等。学习交流加群风哥微信: itpux-com

YashanDB会话的特点：

  • 每个会话都有一个唯一的会话ID
  • 会话可以执行SQL语句和事务
  • 会话会占用数据库连接资源
  • 会话状态包括活跃、空闲、等待等

1.2 YashanDB锁概念

YashanDB锁是数据库为了保证数据一致性和并发控制而实现的机制。当多个会话同时访问同一数据时，锁可以防止数据不一致和冲突。

YashanDB锁的作用：

  • 保证数据一致性
  • 控制并发访问
  • 防止数据冲突
  • 确保事务隔离级别

1.3 YashanDB锁类型

YashanDB的主要锁类型：

# YashanDB锁类型

## 1. 表级锁
– ACCESS SHARE：读表锁，允许其他会话读取但不允许修改
– ROW SHARE：行共享锁，允许其他会话读取和修改其他行
– ROW EXCLUSIVE：行排他锁，允许其他会话读取但不允许获取表级写锁
– SHARE UPDATE EXCLUSIVE：共享更新排他锁，防止其他会话获取SHARE锁
– SHARE：共享锁，允许其他会话读取但不允许修改
– SHARE ROW EXCLUSIVE：共享行排他锁，比SHARE锁更严格
– EXCLUSIVE：排他锁，不允许其他会话访问
– ACCESS EXCLUSIVE：访问排他锁，最严格的表级锁

## 2. 行级锁
– FOR UPDATE：行级排他锁，防止其他会话修改或锁定该行
– FOR SHARE：行级共享锁，允许其他会话读取但不允许修改

## 3. 页级锁
– 锁定数据页，适用于批量操作

## 4. 意向锁
– 意向共享锁（IS）：表示会话打算对表中的某些行加共享锁
– 意向排他锁（IX）：表示会话打算对表中的某些行加排他锁
– 共享意向排他锁（SIX）：表示会话持有表级共享锁，并打算对表中的某些行加排他锁

风哥提示：了解YashanDB的锁类型和机制对于分析和解决并发问题至关重要，建议DBA人员熟悉各种锁类型的适用场景和相互关系。学习交流加群风哥QQ113257174

Part02-生产环境规划与建议

2.1 YashanDB会话管理

YashanDB会话管理的关键要素：

# 会话管理

## 1. 连接池配置
– max_connections：最大连接数，根据服务器资源和并发需求设置
– superuser_reserved_connections：为超级用户预留的连接数
– idle_in_transaction_session_timeout：空闲事务会话超时时间
– connect_timeout：连接超时时间

## 2. 会话参数设置
– work_mem：会话级工作内存
– maintenance_work_mem：维护操作的工作内存
– temp_buffers：临时缓冲区大小
– statement_timeout：语句执行超时时间

## 3. 会话监控
– pg_stat_activity：查看当前活跃会话
– pg_stat_user_sessions：查看用户会话统计
– pg_stat_replication：查看复制会话

## 4. 会话管理策略
– 使用连接池减少连接开销
– 设置合理的连接超时时间
– 定期清理空闲会话
– 监控会话资源使用情况

2.2 YashanDB锁管理

YashanDB锁管理的关键要素：

# 锁管理

## 1. 锁监控
– pg_locks：查看当前锁情况
– pg_stat_activity：查看会话等待状态
– pg_blocking_pids：查看阻塞其他会话的进程ID

## 2. 锁配置
– deadlock_timeout：死锁检测超时时间
– max_locks_per_transaction：每个事务的最大锁数
– max_pred_locks_per_transaction：每个事务的最大谓词锁数

## 3. 锁管理策略
– 减少事务持有锁的时间
– 避免长事务
– 使用合适的隔离级别
– 优化SQL语句，减少锁冲突
– 合理设计表结构和索引

## 4. 锁冲突处理
– 识别锁冲突的源头
– 分析锁等待的原因
– 采取措施解决锁冲突
– 预防锁冲突的发生

2.3 YashanDB性能考量

YashanDB会话与锁的性能考量：

  • 连接数控制：过多的连接会消耗系统资源，影响性能
  • 锁竞争：锁竞争会导致会话等待，影响系统并发性能
  • 事务长度：长事务会持有锁的时间较长，增加锁冲突的可能性
  • 隔离级别：不同的隔离级别对锁的使用和性能有不同的影响
  • SQL优化：优化SQL语句可以减少锁的持有时间和范围
  • 索引设计：合理的索引设计可以减少锁的范围
生产环境建议：合理配置会话和锁参数，监控会话和锁的使用情况，及时发现和解决性能问题，确保系统的稳定运行。更多学习教程公众号风哥教程itpux_com

Part03-生产环境项目实施方案

3.1 YashanDB会话分析

YashanDB会话分析的方法和工具：

# 会话分析

## 1. 查看当前会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT * FROM pg_stat_activity;”

## 2. 查看活跃会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT * FROM pg_stat_activity WHERE state = ‘active’;”

## 3. 查看空闲会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT * FROM pg_stat_activity WHERE state = ‘idle’;”

## 4. 查看空闲事务会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT * FROM pg_stat_activity WHERE state = ‘idle in transaction’;”

## 5. 查看长时间运行的会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pid, usename, datname, now() – query_start as duration, query FROM pg_stat_activity WHERE state = ‘active’ AND now() – query_start > interval ‘5 minutes’ ORDER BY duration DESC;”

## 6. 查看会话资源使用情况
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pid, usename, datname, state, query_start, now() – query_start as duration, wait_event, wait_event_type FROM pg_stat_activity;”

## 7. 终止会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE pid = 12345;”

## 8. 会话分析脚本
$ cat > /usr/local/bin/session_analysis.sh << 'EOF' #!/bin/bash # session_analysis.sh # from:www.itpux.com.qq113257174.wx:itpux-com # web: `http://www.fgedu.net.cn` # 数据库连接信息 HOST="localhost" PORT="5432" DATABASE="fgedudb" USER="fgedu" PASSWORD="fgedu123" # 输出文件 OUTPUT_FILE="/var/log/yashanb/session_analysis.log" # 确保输出目录存在 mkdir -p /var/log/yashanb # 记录时间 echo "[$(date '+%Y-%m-%d %H:%M:%S')] Session analysis started" >> $OUTPUT_FILE

# 查看活跃会话
echo “Active sessions:” >> $OUTPUT_FILE
psql -h $HOST -p $PORT -U $USER -d $DATABASE -c “SELECT pid, usename, datname, state, query_start, now() – query_start as duration, query FROM pg_stat_activity WHERE state = ‘active’ ORDER BY duration DESC;” >> $OUTPUT_FILE

# 查看空闲事务会话
echo “\nIdle in transaction sessions:” >> $OUTPUT_FILE
psql -h $HOST -p $PORT -U $USER -d $DATABASE -c “SELECT pid, usename, datname, state, xact_start, now() – xact_start as duration, query FROM pg_stat_activity WHERE state = ‘idle in transaction’ ORDER BY duration DESC;” >> $OUTPUT_FILE

# 查看长时间运行的会话
echo “\nLong running sessions:” >> $OUTPUT_FILE
psql -h $HOST -p $PORT -U $USER -d $DATABASE -c “SELECT pid, usename, datname, now() – query_start as duration, query FROM pg_stat_activity WHERE state = ‘active’ AND now() – query_start > interval ‘5 minutes’ ORDER BY duration DESC;” >> $OUTPUT_FILE

echo “[$(date ‘+%Y-%m-%d %H:%M:%S’)] Session analysis completed” >> $OUTPUT_FILE
echo “—————————————-” >> $OUTPUT_FILE
EOF

3.2 YashanDB锁分析

YashanDB锁分析的方法和工具：

# 锁分析

## 1. 查看当前锁情况
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT * FROM pg_locks;”

## 2. 查看锁等待情况
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT blocked_locks.pid AS blocked_pid, blocked_activity.usename AS blocked_user, blocking_locks.pid AS blocking_pid, blocking_activity.usename AS blocking_user, blocked_activity.query AS blocked_query, blocking_activity.query AS blocking_query FROM pg_catalog.pg_locks blocked_locks JOIN pg_catalog.pg_stat_activity blocked_activity ON blocked_activity.pid = blocked_locks.pid JOIN pg_catalog.pg_locks blocking_locks ON blocking_locks.locktype = blocked_locks.locktype AND blocking_locks.DATABASE IS NOT DISTINCT FROM blocked_locks.DATABASE AND blocking_locks.relation IS NOT DISTINCT FROM blocked_locks.relation AND blocking_locks.page IS NOT DISTINCT FROM blocked_locks.page AND blocking_locks.tuple IS NOT DISTINCT FROM blocked_locks.tuple AND blocking_locks.virtualxid IS NOT DISTINCT FROM blocked_locks.virtualxid AND blocking_locks.transactionid IS NOT DISTINCT FROM blocked_locks.transactionid AND blocking_locks.classid IS NOT DISTINCT FROM blocked_locks.classid AND blocking_locks.objid IS NOT DISTINCT FROM blocked_locks.objid AND blocking_locks.objsubid IS NOT DISTINCT FROM blocked_locks.objsubid AND blocking_locks.pid != blocked_locks.pid JOIN pg_catalog.pg_stat_activity blocking_activity ON blocking_activity.pid = blocking_locks.pid WHERE NOT blocked_locks.GRANTED;”

## 3. 查看阻塞其他会话的进程
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pid, usename, datname, query FROM pg_stat_activity WHERE pid IN (SELECT DISTINCT blocking_locks.pid FROM pg_catalog.pg_locks blocked_locks JOIN pg_catalog.pg_locks blocking_locks ON blocking_locks.locktype = blocked_locks.locktype AND blocking_locks.DATABASE IS NOT DISTINCT FROM blocked_locks.DATABASE AND blocking_locks.relation IS NOT DISTINCT FROM blocked_locks.relation AND blocking_locks.page IS NOT DISTINCT FROM blocked_locks.page AND blocking_locks.tuple IS NOT DISTINCT FROM blocked_locks.tuple AND blocking_locks.virtualxid IS NOT DISTINCT FROM blocked_locks.virtualxid AND blocking_locks.transactionid IS NOT DISTINCT FROM blocked_locks.transactionid AND blocking_locks.classid IS NOT DISTINCT FROM blocked_locks.classid AND blocking_locks.objid IS NOT DISTINCT FROM blocked_locks.objid AND blocking_locks.objsubid IS NOT DISTINCT FROM blocked_locks.objsubid AND blocking_locks.pid != blocked_locks.pid WHERE NOT blocked_locks.GRANTED);”

## 4. 查看表级锁
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT locktype, database, relation::regclass, mode, granted FROM pg_locks WHERE locktype = ‘relation’;”

## 5. 查看行级锁
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT locktype, database, relation::regclass, page, tuple, mode, granted FROM pg_locks WHERE locktype = ‘tuple’;”

## 6. 锁分析脚本
$ cat > /usr/local/bin/lock_analysis.sh << 'EOF' #!/bin/bash # lock_analysis.sh # from:www.itpux.com.qq113257174.wx:itpux-com # web: `http://www.fgedu.net.cn` # 数据库连接信息 HOST="localhost" PORT="5432" DATABASE="fgedudb" USER="fgedu" PASSWORD="fgedu123" # 输出文件 OUTPUT_FILE="/var/log/yashanb/lock_analysis.log" # 确保输出目录存在 mkdir -p /var/log/yashanb # 记录时间 echo "[$(date '+%Y-%m-%d %H:%M:%S')] Lock analysis started" >> $OUTPUT_FILE

# 查看锁等待情况
echo “Lock wait situations:” >> $OUTPUT_FILE
psql -h $HOST -p $PORT -U $USER -d $DATABASE -c “SELECT blocked_locks.pid AS blocked_pid, blocked_activity.usename AS blocked_user, blocking_locks.pid AS blocking_pid, blocking_activity.usename AS blocking_user, blocked_activity.query AS blocked_query, blocking_activity.query AS blocking_query FROM pg_catalog.pg_locks blocked_locks JOIN pg_catalog.pg_stat_activity blocked_activity ON blocked_activity.pid = blocked_locks.pid JOIN pg_catalog.pg_locks blocking_locks ON blocking_locks.locktype = blocked_locks.locktype AND blocking_locks.DATABASE IS NOT DISTINCT FROM blocked_locks.DATABASE AND blocking_locks.relation IS NOT DISTINCT FROM blocked_locks.relation AND blocking_locks.page IS NOT DISTINCT FROM blocked_locks.page AND blocking_locks.tuple IS NOT DISTINCT FROM blocked_locks.tuple AND blocking_locks.virtualxid IS NOT DISTINCT FROM blocked_locks.virtualxid AND blocking_locks.transactionid IS NOT DISTINCT FROM blocked_locks.transactionid AND blocking_locks.classid IS NOT DISTINCT FROM blocked_locks.classid AND blocking_locks.objid IS NOT DISTINCT FROM blocked_locks.objid AND blocking_locks.objsubid IS NOT DISTINCT FROM blocked_locks.objsubid AND blocking_locks.pid != blocked_locks.pid JOIN pg_catalog.pg_stat_activity blocking_activity ON blocking_activity.pid = blocking_locks.pid WHERE NOT blocked_locks.GRANTED;” >> $OUTPUT_FILE

# 查看表级锁
echo “\nTable-level locks:” >> $OUTPUT_FILE
psql -h $HOST -p $PORT -U $USER -d $DATABASE -c “SELECT locktype, database, relation::regclass, mode, granted FROM pg_locks WHERE locktype = ‘relation’;” >> $OUTPUT_FILE

# 查看行级锁
echo “\nRow-level locks:” >> $OUTPUT_FILE
psql -h $HOST -p $PORT -U $USER -d $DATABASE -c “SELECT locktype, database, relation::regclass, page, tuple, mode, granted FROM pg_locks WHERE locktype = ‘tuple’;” >> $OUTPUT_FILE
echo “[$(date ‘+%Y-%m-%d %H:%M:%S’)] Lock analysis completed” >> $OUTPUT_FILE
echo “—————————————-” >> $OUTPUT_FILE
EOF

3.3 YashanDB故障排查

YashanDB会话与锁相关的故障排查方法：

# 故障排查

## 1. 会话异常排查
– 查看会话状态：SELECT * FROM pg_stat_activity;
– 查看会话等待事件：SELECT pid, wait_event, wait_event_type FROM pg_stat_activity;
– 查看会话执行的SQL：SELECT pid, query FROM pg_stat_activity;
– 查看会话资源使用：SELECT * FROM pg_stat_user_sessions;

## 2. 锁冲突排查
– 查看锁等待情况：使用pg_locks和pg_stat_activity关联查询
– 识别阻塞源：找出持有锁的会话
– 分析锁冲突原因：查看阻塞和被阻塞会话的SQL
– 解决锁冲突：终止阻塞会话或优化SQL

## 3. 死锁排查
– 查看死锁日志：在数据库日志中查找死锁信息
– 分析死锁原因：查看死锁相关的SQL语句
– 优化SQL语句：减少锁冲突的可能性
– 调整事务隔离级别：根据业务需求选择合适的隔离级别

## 4. 性能问题排查
– 查看慢查询：SELECT * FROM pg_stat_statements ORDER BY mean_time DESC LIMIT 10;
– 查看会话执行计划：EXPLAIN ANALYZE SELECT * FROM table WHERE condition;
– 查看索引使用情况：SELECT * FROM pg_stat_user_indexes;
– 查看表扫描情况：SELECT * FROM pg_stat_user_tables WHERE seq_scan > 0;

风哥提示：故障排查需要综合分析会话和锁的情况，找出问题的根本原因，采取针对性的措施解决问题。from yashanb视频:www.itpux.com

Part04-生产案例与实战讲解

4.1 YashanDB会话异常分析

某企业遇到YashanDB会话异常问题，通过分析找出原因并解决。

# 案例背景
– 业务系统：电商平台
– 数据库：YashanDB 8.0
– 问题现象：系统响应缓慢，数据库连接数达到上限

# 分析步骤

## 1. 查看连接数
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT count(*) FROM pg_stat_activity;”
count
——-
500
(1 row)

## 2. 查看连接状态
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT state, count(*) FROM pg_stat_activity GROUP BY state;”
state | count
———————+——-
active | 20
idle | 450
idle in transaction | 30
(3 rows)

## 3. 查看空闲事务会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pid, usename, datname, state, xact_start, now() – xact_start as duration, query FROM pg_stat_activity WHERE state = ‘idle in transaction’ ORDER BY duration DESC LIMIT 10;”
pid | usename | datname | state | xact_start | duration | query
——-+———+———-+———————–+——————————-+————-+——————————————–
12345 | fgedu | fgedudb | idle in transaction | 2023-10-01 10:00:00.000000+08 | 02:30:00 | BEGIN; INSERT INTO fgedu_orders VALUES (…);
12346 | fgedu | fgedudb | idle in transaction | 2023-10-01 10:15:00.000000+08 | 02:15:00 | BEGIN; UPDATE fgedu_products SET stock = …;
…

## 4. 查看长时间运行的活跃会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pid, usename, datname, now() – query_start as duration, query FROM pg_stat_activity WHERE state = ‘active’ AND now() – query_start > interval ‘5 minutes’ ORDER BY duration DESC;”
pid | usename | datname | duration | query
——-+———+———-+————-+——————————————–
12347 | fgedu | fgedudb | 00:10:00 | SELECT * FROM fgedu_orders WHERE status = …;
12348 | fgedu | fgedudb | 00:08:00 | SELECT * FROM fgedu_products WHERE category = …;
…

## 5. 分析原因
– 连接数达到上限（500）
– 大量空闲事务会话（30个），持有锁资源
– 长时间运行的查询（超过5分钟）

## 6. 解决方案

### 6.1 终止空闲事务会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE state = ‘idle in transaction’ AND now() – xact_start > interval ’10 minutes’;”

### 6.2 终止长时间运行的查询
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE state = ‘active’ AND now() – query_start > interval ’10 minutes’;”

### 6.3 优化SQL语句
– 为fgedu_orders表的status字段创建索引
– 为fgedu_products表的category字段创建索引
– 优化查询语句，减少返回数据量

### 6.4 调整参数
$ cat >> /yashanb/fgdata/fgedudb/postgresql.conf << EOF # 会话参数 idle_in_transaction_session_timeout = 600000 # 10分钟 statement_timeout = 300000 # 5分钟 max_connections = 1000 # 增加最大连接数 EOF ### 6.5 配置连接池 - 使用PgBouncer作为连接池 - 配置合理的连接池大小 ## 7. 验证解决方案 - 查看连接数：SELECT count(*) FROM pg_stat_activity; - 查看会话状态：SELECT state, count(*) FROM pg_stat_activity GROUP BY state; - 测试系统响应时间

4.2 YashanDB锁等待分析

某企业遇到YashanDB锁等待问题，通过分析找出原因并解决。

# 案例背景
– 业务系统：金融交易系统
– 数据库：YashanDB 8.0
– 问题现象：系统出现大量锁等待，事务执行缓慢

# 分析步骤

## 1. 查看锁等待情况
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT blocked_locks.pid AS blocked_pid, blocked_activity.usename AS blocked_user, blocking_locks.pid AS blocking_pid, blocking_activity.usename AS blocking_user, blocked_activity.query AS blocked_query, blocking_activity.query AS blocking_query FROM pg_catalog.pg_locks blocked_locks JOIN pg_catalog.pg_stat_activity blocked_activity ON blocked_activity.pid = blocked_locks.pid JOIN pg_catalog.pg_locks blocking_locks ON blocking_locks.locktype = blocked_locks.locktype AND blocking_locks.DATABASE IS NOT DISTINCT FROM blocked_locks.DATABASE AND blocking_locks.relation IS NOT DISTINCT FROM blocked_locks.relation AND blocking_locks.page IS NOT DISTINCT FROM blocked_locks.page AND blocking_locks.tuple IS NOT DISTINCT FROM blocked_locks.tuple AND blocking_locks.virtualxid IS NOT DISTINCT FROM blocked_locks.virtualxid AND blocking_locks.transactionid IS NOT DISTINCT FROM blocked_locks.transactionid AND blocking_locks.classid IS NOT DISTINCT FROM blocked_locks.classid AND blocking_locks.objid IS NOT DISTINCT FROM blocked_locks.objid AND blocking_locks.objsubid IS NOT DISTINCT FROM blocked_locks.objsubid AND blocking_locks.pid != blocked_locks.pid JOIN pg_catalog.pg_stat_activity blocking_activity ON blocking_activity.pid = blocking_locks.pid WHERE NOT blocked_locks.GRANTED;”
blocked_pid | blocked_user | blocking_pid | blocking_user | blocked_query | blocking_query
————-+————–+————–+—————+———————————-+———————————-
12345 | fgedu | 12346 | fgedu | UPDATE fgedu_accounts SET balance = balance + 100 WHERE id = 1; | UPDATE fgedu_accounts SET balance = balance – 50 WHERE id = 1;
12347 | fgedu | 12346 | fgedu | SELECT * FROM fgedu_accounts WHERE id = 1 FOR UPDATE; | UPDATE fgedu_accounts SET balance = balance – 50 WHERE id = 1;
12348 | fgedu | 12346 | fgedu | UPDATE fgedu_accounts SET status = ‘active’ WHERE id = 1; | UPDATE fgedu_accounts SET balance = balance – 50 WHERE id = 1;

## 2. 查看阻塞会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pid, usename, datname, state, xact_start, now() – xact_start as duration, query FROM pg_stat_activity WHERE pid = 12346;”
pid | usename | datname | state | xact_start | duration | query
——-+———+———-+——–+——————————-+————-+——————————————–
12346 | fgedu | fgedudb | active | 2023-10-01 11:00:00.000000+08 | 00:30:00 | UPDATE fgedu_accounts SET balance = balance – 50 WHERE id = 1;

## 3. 分析原因
– 会话12346执行UPDATE操作，持有行级排他锁
– 会话12345、12347、12348等待该锁释放
– 阻塞会话的事务运行时间过长（30分钟）

## 4. 解决方案

### 4.1 终止阻塞会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pg_terminate_backend(12346);”

### 4.2 分析阻塞原因
– 检查应用代码，找出事务长时间运行的原因
– 优化UPDATE语句，减少执行时间
– 调整事务逻辑，减少事务持有锁的时间

### 4.3 优化表结构和索引
– 为fgedu_accounts表的id字段创建索引
– 分析表结构，确保主键和索引设计合理

### 4.4 调整参数
$ cat >> /yashanb/fgdata/fgedudb/postgresql.conf << EOF # 锁参数 deadlock_timeout = 10000 # 10秒 tx_timeout = 300000 # 5分钟 EOF ## 5. 验证解决方案 - 查看锁等待情况：SELECT * FROM pg_locks WHERE NOT granted; - 测试事务执行时间 - 监控系统性能

4.3 YashanDB死锁处理

某企业遇到YashanDB死锁问题，通过分析找出原因并解决。

# 案例背景
– 业务系统：库存管理系统
– 数据库：YashanDB 8.0
– 问题现象：系统出现死锁，事务被回滚

# 分析步骤

## 1. 查看死锁日志
$ tail -n 100 /yashanb/app/yasdb/log/yasdb.log
2023-10-01 12:00:00.000 CST [12345] ERROR: deadlock detected
2023-10-01 12:00:00.000 CST [12345] DETAIL: Process 12345 waits for ShareLock on transaction 12346; blocked by process 12346.
Process 12346 waits for ShareLock on transaction 12345; blocked by process 12345.
2023-10-01 12:00:00.000 CST [12345] HINT: See server log for query details.
2023-10-01 12:00:00.000 CST [12345] CONTEXT: while updating tuple (0,1) in relation “fgedu_inventory”
2023-10-01 12:00:00.000 CST [12345] STATEMENT: UPDATE fgedu_inventory SET quantity = quantity – 1 WHERE product_id = 1;

## 2. 查看相关会话
$ /yashanb/app/yasdb/bin/psql -U yasdb -d fgedudb -c “SELECT pid, usename, datname, state, xact_start, query FROM pg_stat_activity WHERE pid IN (12345, 12346);”
pid | usename | datname | state | xact_start | query
——-+———+———-+——–+——————————-+——————————————–
12345 | fgedu | fgedudb | active | 2023-10-01 11:59:50.000000+08 | BEGIN; UPDATE fgedu_inventory SET quantity = quantity – 1 WHERE product_id = 1; UPDATE fgedu_inventory SET quantity = quantity + 1 WHERE product_id = 2;
12346 | fgedu | fgedudb | active | 2023-10-01 11:59:55.000000+08 | BEGIN; UPDATE fgedu_inventory SET quantity = quantity – 1 WHERE product_id = 2; UPDATE fgedu_inventory SET quantity = quantity + 1 WHERE product_id = 1;

## 3. 分析原因
– 会话12345持有product_id=1的锁，等待product_id=2的锁
– 会话12346持有product_id=2的锁，等待product_id=1的锁
– 形成循环等待，导致死锁

## 4. 解决方案

### 4.1 优化事务逻辑
– 统一更新顺序：所有事务按照相同的顺序更新记录
– 例如：先更新product_id较小的记录，再更新product_id较大的记录

### 4.2 减少事务范围
– 将大事务拆分为小事务
– 只在必要时持有锁

### 4.3 调整隔离级别
– 使用较低的隔离级别，如READ COMMITTED
– 避免使用SERIALIZABLE隔离级别

### 4.4 优化SQL语句
– 确保WHERE子句使用索引
– 减少锁定的行数

## 5. 验证解决方案
– 修改应用代码，统一更新顺序
– 测试并发事务，确认死锁不再发生
– 监控系统性能

Part05-风哥经验总结与分享

5.1 YashanDB会话与锁最佳实践

YashanDB会话与锁的最佳实践：

  • 合理配置连接池：使用连接池管理数据库连接，减少连接开销
  • 控制连接数：根据服务器资源和并发需求设置合理的最大连接数
  • 及时释放连接：使用完连接后及时释放，避免空闲连接占用资源
  • 减少事务长度：保持事务短小，减少锁的持有时间
  • 统一锁定顺序：所有事务按照相同的顺序锁定资源，避免死锁
  • 使用合适的隔离级别：根据业务需求选择合适的隔离级别
  • 优化SQL语句：使用索引，减少全表扫描，减少锁的范围
  • 定期监控：定期监控会话和锁的使用情况，及时发现问题
  • 设置合理的超时时间：为事务和语句设置合理的超时时间
  • 培训开发人员：培训开发人员了解数据库锁机制，编写高效的SQL语句
持续优化：会话与锁的管理是一个持续的过程，需要根据业务发展和系统运行情况不断优化。建议定期review会话和锁的使用情况，及时调整配置和策略。

5.2 YashanDB会话与锁常见问题

YashanDB会话与锁的常见问题及解决方案：

# 常见问题及解决方案

## 1. 连接数达到上限
– 原因：应用程序没有正确释放连接，连接池配置不合理
– 解决方案：
– 检查应用程序代码，确保正确释放连接
– 调整连接池配置，设置合理的最大连接数
– 增加数据库服务器资源

## 2. 大量空闲事务会话
– 原因：应用程序没有正确提交或回滚事务
– 解决方案：
– 检查应用程序代码，确保事务正确提交或回滚
– 设置idle_in_transaction_session_timeout参数
– 定期清理空闲事务会话

## 3. 锁等待时间过长
– 原因：事务持有锁的时间过长，锁冲突严重
– 解决方案：
– 优化SQL语句，减少执行时间
– 减少事务长度，及时提交或回滚
– 优化表结构和索引，减少锁的范围

## 4. 死锁
– 原因：事务之间形成循环等待
– 解决方案：
– 统一锁定顺序
– 减少事务范围
– 使用较低的隔离级别
– 优化SQL语句

## 5. 性能下降
– 原因：锁竞争严重，会话等待时间长
– 解决方案：
– 优化SQL语句，减少锁冲突
– 增加数据库服务器资源
– 考虑使用读写分离
– 优化表结构和索引

5.3 YashanDB会话与锁优化建议

YashanDB会话与锁的优化建议：

# 优化建议

## 1. 会话优化
– 使用连接池：减少连接开销，提高连接复用率
– 合理配置连接参数：根据业务需求设置max_connections、idle_in_transaction_session_timeout等参数
– 监控会话状态：定期检查会话状态，及时清理异常会话
– 优化应用代码：确保正确管理连接和事务

## 2. 锁优化
– 减少锁持有时间：保持事务短小，及时提交或回滚
– 减少锁范围：使用索引，避免全表扫描，减少锁定的行数
– 统一锁定顺序：所有事务按照相同的顺序锁定资源
– 使用合适的锁类型：根据业务需求选择合适的锁类型
– 优化隔离级别：根据业务需求选择合适的隔离级别

## 3. SQL优化
– 使用索引：为频繁查询的字段创建索引
– 优化查询语句：减少返回数据量，使用分页查询
– 避免长事务：将大事务拆分为小事务
– 避免全表扫描：使用WHERE子句过滤数据
– 使用EXPLAIN分析执行计划：优化SQL执行计划

## 4. 系统优化
– 增加服务器资源：根据业务需求增加CPU、内存、磁盘等资源
– 配置合理的内核参数：根据服务器硬件配置调整内核参数
– 使用存储优化：使用SSD存储，提高I/O性能
– 考虑分区表：对大表使用分区表，提高查询性能

## 5. 监控与维护
– 定期监控会话和锁的使用情况：使用Zabbix、Grafana等工具监控
– 定期分析慢查询：找出性能瓶颈，优化SQL语句
– 定期维护数据库：执行VACUUM、ANALYZE等维护操作
– 定期备份：确保数据安全

风哥提示：会话与锁的管理是数据库性能优化的重要组成部分，需要DBA人员和开发人员共同努力，确保系统的稳定运行和良好的性能。建议建立完善的监控和维护机制，及时发现和解决问题。

本文由风哥教程整理发布,仅用于学习测试使用,转载注明出处:http://www.fgedu.net.cn/10327.html

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