Python流式游标与缓存式(默认)游标的那些坑及解决

	#这是一个类方法里面的内容，简化版
  			sql = "select * from storys"
        try:
            # 获取一个链接，一个cursor，执行SQL语句，MysqlController为封装的数据库连接池处理工具
            conn = MysqlController.getConn()
            cursor = conn.cursor()
            cursor.execute(sql)

            #信号锁
            semaphore = threading.BoundedSemaphore(self.maxRunThread)

            while(True):
                result = cursor.fetchone()
                if not result:
                    break
#这里不是重点
#———————————————————————————————————————————————————————————————————————————————————————————
                #这是一个for循环，里面开启了10个线程，每次开启线程之前要求获得到信号锁。
  							#每个线程run方法结束之后会调用semaphore.release()，以此保证同时运行的线程不超过self.maxRunThread个
                for i in range(10):
                    semaphore.acquire()
                    t = threading.Thread(target=self.run, args=(semaphore,i))
                    t.start()
#———————————————————————————————————————————————————————————————————————————————————————————

            print('结束')
            cursor.close()
            conn.close()
        except Exception as e:
            print(e)

import pymysql
import time

def mytest():
    connection = pymysql.connect(
    host='localhost',
    port=3306,
    user='root',
    password='',
    db='*******',
    charset='utf8')
    cursor = connection.cursor()
    cursor.execute("select * from storys limit 10")
    data = cursor.fetchone()
    i = 0
    while data != None:
        if(i == 3):
            connection.close()
            print('connection is close')
        print(data[0])
        i+=1
        data = cursor.fetchone()
    cursor.close()
    connection.close()

if __name__ == '__main__':
    mytest()

cursor = connection.cursor()

cursor = conn.cursor(pymysql.cursors.SSDictCursor)#返回字典式数据

	#这是一个类方法里面的内容，简化版
  			sql = "select * from storys"
        try:
            # 获取一个链接，一个cursor，执行SQL语句，MysqlController为封装的数据库连接池处理工具
            conn = MysqlController.getConn()
            cursor = conn.cursor(pymysql.cursors.SSDictCursor)#这里改游标类型了！！！！！！！
            cursor.execute(sql)

            while(True):
              	conn.ping()# 就是这句话！！！！！！！！！画蛇添足！！！！！！！正确代码去掉这句话
                result = cursor.fetchone()
                if not result:
                    break
								#做了一些事儿

            print('结束')
            cursor.close()
            conn.close()
        except Exception as e:
            print(e)