需求场景：

有一业务数据库，使用MySQL 5.5版本，每天会写入大量数据，需要不定期将多表中“指定时期前“的数据进行删除，在SQL SERVER中很容易实现，写几个WHILE循环就搞定，虽然MySQL中也存在类似功能，怎奈自己不精通，于是采用Python来实现

话不多少，上脚本：

# coding: utf-8
import MySQLdb
import time

# delete config
DELETE_DATETIME = '2016-08-31 23:59:59'
DELETE_ROWS = 10000
EXEC_DETAIL_FILE = 'exec_detail.txt'
SLEEP_SECOND_PER_BATCH = 0.5

DATETIME_FORMAT = '%Y-%m-%d %X'
# MySQL Connection Config
Default_MySQL_Host = 'localhost'
Default_MySQL_Port = 3358
Default_MySQL_User = "root"
Default_MySQL_Password = 'roo@01239876'
Default_MySQL_Charset = "utf8"
Default_MySQL_Connect_TimeOut = 120
Default_Database_Name = 'testdb001'


def get_time_string(dt_time):
    """
    获取指定格式的时间字符串
    :param dt_time: 要转换成字符串的时间
    :return: 返回指定格式的字符串
    """
    global DATETIME_FORMAT
    return time.strftime(DATETIME_FORMAT, dt_time)


def print_info(message):
    """
    将message输出到控制台，并将message写入到日志文件
    :param message: 要输出的字符串
    :return: 无返回
    """
    print(message)
    global EXEC_DETAIL_FILE
    new_message = get_time_string(time.localtime()) + chr(13) + str(message)
    write_file(EXEC_DETAIL_FILE, new_message)


def write_file(file_path, message):
    """
    将传入的message追加写入到file_path指定的文件中
    请先创建文件所在的目录
    :param file_path: 要写入的文件路径
    :param message: 要写入的信息
    :return:
    """
    file_handle = open(file_path, 'a')
    file_handle.writelines(message)
    # 追加一个换行以方便浏览
    file_handle.writelines(chr(13))
    file_handle.close()


def get_mysql_connection():
    """
    根据默认配置返回数据库连接
    :return: 数据库连接
    """
    conn = MySQLdb.connect(
            host=Default_MySQL_Host,
            port=Default_MySQL_Port,
            user=Default_MySQL_User,
            passwd=Default_MySQL_Password,
            connect_timeout=Default_MySQL_Connect_TimeOut,
            charset=Default_MySQL_Charset,
            db=Default_Database_Name
    )
    return conn


def mysql_exec(sql_script, sql_param=None):
    """
    执行传入的脚本，返回影响行数
    :param sql_script:
    :param sql_param:
    :return: 脚本最后一条语句执行影响行数
    """
    try:
        conn = get_mysql_connection()
        print_info("在服务器{0}上执行脚本:{1}".format(
                conn.get_host_info(), sql_script))
        cursor = conn.cursor()
        if sql_param is not None:
            cursor.execute(sql_script, sql_param)
            row_count = cursor.rowcount
        else:
            cursor.execute(sql_script)
            row_count = cursor.rowcount
        conn.commit()
        cursor.close()
        conn.close()
    except Exception, e:
        print_info("execute exception:" + str(e))
        row_count = 0
    return row_count


def mysql_query(sql_script, sql_param=None):
    """
    执行传入的SQL脚本，并返回查询结果
    :param sql_script:
    :param sql_param:
    :return: 返回SQL查询结果
    """
    try:
        conn = get_mysql_connection()
        print_info("在服务器{0}上执行脚本:{1}".format(
                conn.get_host_info(), sql_script))
        cursor = conn.cursor()
        if sql_param != '':
            cursor.execute(sql_script, sql_param)
        else:
            cursor.execute(sql_script)
        exec_result = cursor.fetchall()
        cursor.close()
        conn.close()
        return exec_result
    except Exception, e:
        print_info("execute exception:" + str(e))


def get_id_range(table_name):
    """
    按照传入的表获取要删除数据最大ID、最小ID、删除总行数
    :param table_name: 要删除的表
    :return: 返回要删除数据最大ID、最小ID、删除总行数
    """
    global DELETE_DATETIME
    sql_script = """
SELECT
MAX(ID) AS MAX_ID,
MIN(ID) AS MIN_ID,
COUNT(1) AS Total_Count
FROM {0}
WHERE create_time <='{1}';
""".format(table_name, DELETE_DATETIME)

    query_result = mysql_query(sql_script=sql_script, sql_param=None)
    max_id, min_id, total_count = query_result[0]
    # 此处有一坑，可能出现total_count不为0 但是max_id 和min_id 为None的情况
    # 因此判断max_id和min_id 是否为NULL
    if (max_id is None) or (min_id is None):
        max_id, min_id, total_count = 0, 0, 0
    return max_id, min_id, total_count


def delete_data(table_name):
    max_id, min_id, total_count = get_id_range(table_name)
    temp_id = min_id
    while temp_id <= max_id:
        sql_script = """
DELETE FROM {0}
WHERE id <= {1}
and id >= {2}
AND create_time <='{3}';
        """.format(table_name, temp_id + DELETE_ROWS, temp_id, DELETE_DATETIME)
        temp_id += DELETE_ROWS
        print(sql_script)
        row_count = mysql_exec(sql_script)
        print_info("影响行数：{0}".format(row_count))
        current_percent = (temp_id - min_id) * 1.0 / (max_id - min_id)
        print_info("当前进度{0}/{1},剩余{2},进度为{3}%".format(temp_id, max_id, max_id - temp_id, "%.2f" % current_percent))
        time.sleep(SLEEP_SECOND_PER_BATCH)
    print_info("当前表{0}已无需要删除的数据".format(table_name))


delete_data('TB001')
delete_data('TB002')
delete_data('TB003')

执行效果：

实现原理：

由于表存在自增ID，于是给我们增量循环删除的机会，查找出满足删除条件的最大值ID和最小值ID，然后按ID 依次递增，每次小范围内(如10000条)进行删除。

实现优点：

实现“小斧子砍大柴”的效果，事务小，对线上影响较小，打印出当前处理到的“ID”，可以随时关闭，稍微修改下代码便可以从该ID开始，方便。

实现不足：

为防止主从延迟太高，采用每次删除SLEEP1秒的方式，相对比较糙，最好的方式应该是周期扫描这条复制链路，根据延迟调整SLEEP的周期，反正都脚本化，再智能化点又何妨！