标签：mysql 完成 初始 axshare other 提升 database session toc
DBUtils 是一套用于管理数据库连接池的Python包，为高频度高并发的数据库访问提供更好的性能，可以自动管理连接对象的创建和释放。并允许对非线程安全的数据库接口进行线程安全包装。
DBUtils提供两种外部接口：
实测证明 PersistentDB 的速度是最高的，但是在某些特殊情况下，数据库的连接过程可能异常缓慢，而此时的PooledDB则可以提供相对来说平均连接时间比较短的管理方式。
另外，实际使用的数据库驱动也有所依赖，比如SQLite数据库只能使用PersistentDB作连接池。 下载地址：http://www.webwareforpython.org/downloads/DBUtils/
连接池对象只初始化一次，一般可以作为模块级代码来确保。 PersistentDB的连接例子:
import DBUtils.PersistentDB
persist=DBUtils.PersistentDB.PersistentDB(dbpai=MySQLdb,maxusage=1000,**kwargs)
这里的参数dbpai指使用的底层数据库模块，兼容DB-API的。maxusage则为一个连接最大使用次数，参考了官方例子。后面的**kwargs则为实际传递给MySQLdb的参数。
获取连接: conn=persist.connection() 实际编程中用过的连接直接关闭 conn.close() 即可将连接交还给连接池。
PooledDB使用方法同PersistentDB，只是参数有所不同。
db=pooled.connection()
cur=db.cursor()
cur.execute(sql)
res=cur.fetchone()
cur.close() # or del cur
db.close() # or del db
python不用连接池的MySQL连接方法
import MySQLdb
conn= MySQLdb.connect(host=‘localhost‘,user=‘root‘,passwd=‘pwd‘,db=‘myDB‘,port=3306)
#import pymysql
#conn = pymysql.connect(host=‘localhost‘, port=‘3306‘, db=‘game‘, user=‘root‘, password=‘123456‘, charset=‘utf8‘)
cur=conn.cursor()
SQL="select * from table1"
r=cur.execute(SQL)
r=cur.fetchall()
cur.close()
conn.close()
用连接池后的连接方法
import MySQLdb
from DBUtils.PooledDB import PooledDB
pool = PooledDB(MySQLdb,5,host=‘localhost‘,user=‘root‘,passwd=‘pwd‘,db=‘myDB‘,port=3306) #5为连接池里的最少连接数
conn = pool.connection() #以后每次需要数据库连接就是用connection（）函数获取连接就好了
cur=conn.cursor()
SQL="select * from table1"
r=cur.execute(SQL)
r=cur.fetchall()
cur.close()
conn.close()
DBUtils下载地址：https://pypi.python.org/pypi/DBUtils/
import sys
import threading
import MySQLdb
import DBUtils.PooledDB
connargs = { "host":"localhost", "user":"user1", "passwd":"123456", "db":"test" }
def test(conn):
try:
cursor = conn.cursor()
count = cursor.execute("select * from users")
rows = cursor.fetchall()
for r in rows: pass
finally:
conn.close()
def testloop():
print ("testloop")
for i in range(1000):
conn = MySQLdb.connect(**connargs)
test(conn)
def testpool():
print ("testpool")
pooled = DBUtils.PooledDB.PooledDB(MySQLdb, **connargs)
for i in range(1000):
conn = pooled.connection()
test(conn)
def main():
t = testloop if len(sys.argv) == 1 else testpool
for i in range(10):
threading.Thread(target = t).start()
if __name__ == "__main__":
main()
看看 10 线程的测试结果。
$ time ./main.py
testloop
testloop
testloop
testloop
testloop
testloop
testloop
testloop
testloop
testloop
real 0m4.471s
user 0m0.570s
sys 0m4.670s
$ time ./main.py -l
testpool
testpool
testpool
testpool
testpool
testpool
testpool
testpool
testpool
testpool
real 0m2.637s
user 0m0.320s
sys 0m2.750s
虽然测试方式不是很严谨，但从测试结果还是能感受到 DBUtils 带来的性能提升。当然，我们我们也可以在 testloop() 中一直重复使用一个不关闭的 Connection，但这却不适合实际开发时的情形。
DBUtils 提供了几个参数，便于我们更好地调整资源利用。
DBUtils.PooledDB.PooledDB(self, creator,
mincached=0, maxcached=0, maxshared=0, maxconnections=0, blocking=False, maxusage=None,
setsession=None, failures=None, *args, **kwargs)
Docstring:
Set up the DB-API 2 connection pool.
creator: either an arbitrary function returning new DB-API 2
connection objects or a DB-API 2 compliant database module
mincached: initial number of idle connections in the pool
(0 means no connections are made at startup)
maxcached: maximum number of idle connections in the pool
(0 or None means unlimited pool size)
maxshared: maximum number of shared connections
(0 or None means all connections are dedicated)
When this maximum number is reached, connections are
shared if they have been requested as shareable.
maxconnections: maximum number of connections generally allowed
(0 or None means an arbitrary number of connections)
blocking: determines behavior when exceeding the maximum
(if this is set to true, block and wait until the number of
connections decreases, otherwise an error will be reported)
maxusage: maximum number of reuses of a single connection
(0 or None means unlimited reuse)
When this maximum usage number of the connection is reached,
the connection is automatically reset (closed and reopened).
setsession: optional list of SQL commands that may serve to prepare
the session, e.g. ["set datestyle to ...", "set time zone ..."]
failures: an optional exception class or a tuple of exception classes
for which the connection failover mechanism shall be applied,
if the default (OperationalError, InternalError) is not adequate
args, kwargs: the parameters that shall be passed to the creator
function or the connection constructor of the DB-API 2 module
DBUtils 仅提供给了连接池管理，实际的数据库操作依然是由符合 DB-API 2 标准的目标数据库模块完成的。
一个面向对象使用DBUtils的栗子
# coding=utf-8
"""
使用DBUtils数据库连接池中的连接，操作数据库
OperationalError: (2006, ‘MySQL server has gone away’)
"""
import json
import pymysql
import datetime
from DBUtils.PooledDB import PooledDB
import pymysql
class MysqlClient(object):
__pool = None;
def __init__(self, mincached=10, maxcached=20, maxshared=10, maxconnections=200, blocking=True,
maxusage=100, setsession=None, reset=True,
host=‘127.0.0.1‘, port=3306, db=‘test‘,
user=‘root‘, passwd=‘123456‘, charset=‘utf8mb4‘):
"""
:param mincached:连接池中空闲连接的初始数量
:param maxcached:连接池中空闲连接的最大数量
:param maxshared:共享连接的最大数量
:param maxconnections:创建连接池的最大数量
:param blocking:超过最大连接数量时候的表现，为True等待连接数量下降，为false直接报错处理
:param maxusage:单个连接的最大重复使用次数
:param setsession:optional list of SQL commands that may serve to prepare
the session, e.g. ["set datestyle to ...", "set time zone ..."]
:param reset:how connections should be reset when returned to the pool
(False or None to rollback transcations started with begin(),
True to always issue a rollback for safety‘s sake)
:param host:数据库ip地址
:param port:数据库端口
:param db:库名
:param user:用户名
:param passwd:密码
:param charset:字符编码
"""
if not self.__pool:
self.__class__.__pool = PooledDB(pymysql,
mincached, maxcached,
maxshared, maxconnections, blocking,
maxusage, setsession, reset,
host=host, port=port, db=db,
user=user, passwd=passwd,
charset=charset,
cursorclass=pymysql.cursors.DictCursor
)
self._conn = None
self._cursor = None
self.__get_conn()
def __get_conn(self):
self._conn = self.__pool.connection();
self._cursor = self._conn.cursor();
def close(self):
try:
self._cursor.close()
self._conn.close()
except Exception as e:
print e
def __execute(self, sql, param=()):
count = self._cursor.execute(sql, param)
print count
return count
@staticmethod
def __dict_datetime_obj_to_str(result_dict):
"""把字典里面的datatime对象转成字符串，使json转换不出错"""
if result_dict:
result_replace = {k: v.__str__() for k, v in result_dict.items() if isinstance(v, datetime.datetime)}
result_dict.update(result_replace)
return result_dict
def select_one(self, sql, param=()):
"""查询单个结果"""
count = self.__execute(sql, param)
result = self._cursor.fetchone()
""":type result:dict"""
result = self.__dict_datetime_obj_to_str(result)
return count, result
def select_many(self, sql, param=()):
"""
查询多个结果
:param sql: qsl语句
:param param: sql参数
:return: 结果数量和查询结果集
"""
count = self.__execute(sql, param)
result = self._cursor.fetchall()
""":type result:list"""
[self.__dict_datetime_obj_to_str(row_dict) for row_dict in result]
return count, result
def execute(self, sql, param=()):
count = self.__execute(sql, param)
return count
def begin(self):
"""开启事务"""
self._conn.autocommit(0)
def end(self, option=‘commit‘):
"""结束事务"""
if option == ‘commit‘:
self._conn.autocommit()
else:
self._conn.rollback()
if __name__ == "__main__":
mc = MysqlClient()
sql1 = ‘SELECT * FROM shiji WHERE id = 1‘
result1 = mc.select_one(sql1)
print json.dumps(result1[1], ensure_ascii=False)
sql2 = ‘SELECT * FROM shiji WHERE id IN (%s,%s,%s)‘
param = (2, 3, 4)
print json.dumps(mc.select_many(sql2, param)[1], ensure_ascii=False)
标签：mysql 完成 初始 axshare other 提升 database session toc
原文地址：https://www.cnblogs.com/geoffreygao/p/13530088.html
