详解如何诊断和解决PostgreSQL中的死锁问题

DETAIL:  Process <pid1> waits for ShareLock on transaction <txid1>; blocked by process <pid2>.
Process <pid2> waits for ShareLock on transaction <txid2>; blocked by process <pid1>.

SELECT * FROM pg_stat_activity;

SELECT * FROM pg_locks;

log_lock_waits = on
deadlock_timeout = 1s

BEGIN;
-- 获取表 A 的排他锁
LOCK TABLE A IN EXCLUSIVE MODE;
-- 这里做一些操作

-- 暂停一段时间，模拟其他操作
SELECT pg_sleep(5);

-- 尝试获取表 B 的排他锁
LOCK TABLE B IN EXCLUSIVE MODE;
COMMIT;

BEGIN;
-- 获取表 B 的排他锁
LOCK TABLE B IN EXCLUSIVE MODE;
-- 这里做一些操作

-- 暂停一段时间，模拟其他操作
SELECT pg_sleep(5);

-- 尝试获取表 A 的排他锁
LOCK TABLE A IN EXCLUSIVE MODE;
COMMIT;

BEGIN;
-- 获取表 A 的排他锁
LOCK TABLE A IN EXCLUSIVE MODE;
-- 获取表 B 的排他锁
LOCK TABLE B IN EXCLUSIVE MODE;
COMMIT;

BEGIN;
-- 获取表 A 的排他锁
LOCK TABLE A IN EXCLUSIVE MODE;
-- 获取表 B 的排他锁
LOCK TABLE B IN EXCLUSIVE MODE;
COMMIT;

BEGIN;
-- 步骤 1：数据读取和计算
SELECT * FROM some_table WHERE some_condition;
-- 提交事务
COMMIT;

BEGIN;
-- 步骤 2：基于步骤 1 的结果进行数据更新
UPDATE some_table SET some_column = some_value WHERE some_other_condition;
COMMIT;

import psycopg2
import time
import random

def execute_transaction(conn, query):
    max_retries = 5
    retry_delay = 1  # 初始重试延迟时间（秒）

    for retry in range(max_retries):
        try:
            with conn.cursor() as cur:
                cur.execute(query)
                conn.commit()
            return  # 成功执行，退出函数
        except psycopg2.Error as e:
            conn.rollback()
            if "deadlock detected" in str(e):
                if retry < max_retries - 1:
                    delay = retry_delay * (2 ** retry) + random.randint(0, 1000) / 1000
                    print(f"死锁发生，重试第 {retry + 1} 次，等待 {delay} 秒...")
                    time.sleep(delay)
                    retry_delay *= 2
                else:
                    raise e  # 达到最大重试次数，抛出异常
            else:
                raise e  # 其他错误，抛出异常

# 示例用法
conn = psycopg2.connect(database="your_database", user="your_user", password="your_password", host="your_host", port="your_port")
query = "your_transaction_query"
execute_transaction(conn, query)

conn = psycopg2.connect(database="your_database", user="your_user", password="your_password", host="your_host", port="your_port", options="-c lock_timeout=5000")