【python下用sqlite3, 多线程下报错，原因和解决 】

在python下用sqlite3, 多线程 在UPDATE 或者INSERT的时候, 会报错

sqlite3.OperationalError: cannot commit - no transaction is active

1. 原因

多线程写冲突

• 非原子写操作：如果多个线程同时执行非原子写操作，可能会导致数据覆盖或不一致。

2. 解决方案

使用锁

使用锁来确保同一时间只有一个线程可以执行写操作。

import sqlite3
import threading

lock = threading.Lock()

def worker(conn, thread_id):
    with lock:
        cursor = conn.cursor()
        cursor.execute("INSERT INTO test (id, value) VALUES (?, ?)", (thread_id, f"value_{thread_id}"))
        conn.commit()
        cursor.close()

def main():
    conn = sqlite3.connect('example.db', check_same_thread=False)
    cursor = conn.cursor()
    cursor.execute("CREATE TABLE IF NOT EXISTS test (id INTEGER PRIMARY KEY, value TEXT)")
    conn.commit()
    cursor.close()

    threads = []
    for i in range(5):
        thread = threading.Thread(target=worker, args=(conn, i))
        threads.append(thread)
        thread.start()

    for thread in threads:
        thread.join()

    conn.close()

if __name__ == "__main__":
    main()

使用事务

显式事务管理：在每个线程中显式地开始和提交事务，确保事务的原子性和一致性。

import sqlite3
import threading

def worker(conn, thread_id):
    cursor = conn.cursor()
    cursor.execute("BEGIN")
    cursor.execute("INSERT INTO test (id, value) VALUES (?, ?)", (thread_id, f"value_{thread_id}"))
    conn.commit()
    cursor.close()

def main():
    conn = sqlite3.connect('example.db', check_same_thread=False)
    cursor = conn.cursor()
    cursor.execute("CREATE TABLE IF NOT EXISTS test (id INTEGER PRIMARY KEY, value TEXT)")
    conn.commit()
    cursor.close()

    threads = []
    for i in range(5):
        thread = threading.Thread(target=worker, args=(conn, i))
        threads.append(thread)
        thread.start()

    for thread in threads:
        thread.join()

    conn.close()

if __name__ == "__main__":
    main()