PyMysql error : Packet Sequence Number Wrong - got 1 expected 0

错误一

错误原因

pymysql的主进程启动的connect无法给子进程中使用，所以读取大批量数据时最后容易出现了此类问题。

解决方案

换成pymysql-pool可以解决方法：
具体如下：

pip install pymysql-pool

代码如下：

import pymysql
import pymysqlpool

def select_ebay_catelotory():
    config={'host': HOST, 'user': USER, 'password': PASSWD, 'database': DB, 'autocommit':True}
    pool1 = pymysqlpool.ConnectionPool(size=10, maxsize=20, pre_create_num=2, name='pool1', **config)
    con1 = pool1.get_connection()
    gcu = con1.cursor()
    try:
        gcu.execute(f"""SELECT *** """)

        # 获取剩余结果所有数据
        rows = gcu.fetchall()
    except Exception as e:
        print(e)
    finally:
        # gcu.close()
        con1.close()
    return rows

错误二

原因

要读取的内容太大了。有两类：某列太长了，总行数太多了。

如何确定？
你的代码读取100行没问题，1000行也没问题，10000行也没问题，100万行就有问题了。那就是这个原因。

解决方案

不要limit去读，太费时间：先取id，再用id去分批读取数据。

import pymysql
import pymysqlpool

def select_all_ids():
    config={'host': HOST, 'user': USER, 'password': PASSWD, 'database': DB, 'autocommit':True}
    pool1 = pymysqlpool.ConnectionPool(size=35, maxsize=35, pre_create_num=2, name='pool1', **config)
    con1 = pool1.get_connection()
    gcu = con1.cursor()
    try:
        gcu.execute(f"""SELECT `id` FROM sfc_minesweeper.product_detail WHERE create_time>'2024-07-10' AND CHAR_LENGTH(result_data)>500""")

        # 获取剩余结果所有数据
        rows = gcu.fetchall()
    except Exception as e:
        print(e)
    finally:
        # gcu.close()
        con1.close()
    return rows


def select_ebay_catelotory(pids):
    config={'host': HOST, 'user': USER, 'password': PASSWD, 'database': DB, 'autocommit':True}
    pool1 = pymysqlpool.ConnectionPool(size=35, maxsize=35, pre_create_num=2, name='pool1', **config)
    con1 = pool1.get_connection()
    gcu = con1.cursor()
    try:
        gcu.execute(f"""SELECT `id`, `result_data`, `product_offer_id` FROM sfc_minesweeper.product_detail WHERE id in {tuple(pids)}""")

        # 获取剩余结果所有数据
        rows = gcu.fetchall()
    except Exception as e:
        print(e)
    finally:
        # gcu.close()
        con1.close()
    return rows

# 先拿到所有id
pd_ids = [e[0] for e in select_all_ids()]
# 再分批读取
pd1688s = []
step = 4000
for begin in range(0, len(pd_ids), step):
    pd1688s.extend([e for e in select_ebay_catelotory(pd_ids[begin:begin+step])])
    print(i, len(pd1688s))