Mysql Flask SQLAlchemy查询成本-Unicode转换
我是数据库新手,我正在尝试在Flask SQLalchemy(Python 2.7)应用程序中加快查询速度。我已经分析了代码,但不知道如何解释它。我想了解更多关于这个主题的一般性技巧,但我的具体问题是:查询的“string_decoder”执行时间似乎非常昂贵,我假设它正在将字符串转换为unicode,以便以unicode格式返回它们Mysql Flask SQLAlchemy查询成本-Unicode转换,mysql,sql,python-2.7,unicode,flask-sqlalchemy,Mysql,Sql,Python 2.7,Unicode,Flask Sqlalchemy,我是数据库新手,我正在尝试在Flask SQLalchemy(Python 2.7)应用程序中加快查询速度。我已经分析了代码,但不知道如何解释它。我想了解更多关于这个主题的一般性技巧,但我的具体问题是:查询的“string_decoder”执行时间似乎非常昂贵,我假设它正在将字符串转换为unicode,以便以unicode格式返回它们 259619 function calls (259567 primitive calls) in 1.108 seconds
259619 function calls (259567 primitive calls) in 1.108 seconds
Ordered by: cumulative time
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.007 0.007 1.108 1.108 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py:2235(all)
5947 0.019 0.000 0.651 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/loading.py:27(instances)
5946 0.116 0.000 0.515 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/loading.py:323(_instance)
1 0.000 0.000 0.449 0.449 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py:2348(__iter__)
1 0.000 0.000 0.448 0.448 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/query.py:2362(_execute_and_instances)
1 0.000 0.000 0.448 0.448 /usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py:597(execute)
1 0.000 0.000 0.448 0.448 /usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py:727(_execute_clauseelement)
1 0.000 0.000 0.446 0.446 /usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py:812(_execute_context)
1 0.000 0.000 0.445 0.445 /usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/default.py:323(do_execute)
1 0.000 0.000 0.445 0.445 /usr/local/lib/python2.7/dist-packages/MySQLdb/cursors.py:164(execute)
1 0.000 0.000 0.445 0.445 /usr/local/lib/python2.7/dist-packages/MySQLdb/cursors.py:343(_query)
1 0.000 0.000 0.427 0.427 /usr/local/lib/python2.7/dist-packages/MySQLdb/cursors.py:348(_post_get_result)
1 0.000 0.000 0.427 0.427 /usr/local/lib/python2.7/dist-packages/MySQLdb/cursors.py:314(_fetch_row)
1 0.068 0.068 0.427 0.427 {built-in method fetch_row}
5946 0.092 0.000 0.231 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/loading.py:280(populate_state)
12547 0.040 0.000 0.208 0.000 /usr/local/lib/python2.7/dist-packages/MySQLdb/connections.py:206(string_decoder)
12547 0.053 0.000 0.168 0.000 {method 'decode' of 'str' objects}
5946 0.121 0.000 0.152 0.000 /usr/local/lib/python2.7/dist-packages/MySQLdb/times.py:44(DateTime_or_None)
12547 0.064 0.000 0.115 0.000 /usr/lib/python2.7/encodings/utf_8.py:15(decode)
53514 0.086 0.000 0.086 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/strategies.py:150(fetch_col)
5946 0.038 0.000 0.085 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/instrumentation.py:286(new_instance)
1 0.037 0.037 0.070 0.070 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/state.py:505(_commit_all_states)
5946 0.015 0.000 0.052 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/strategies.py:619(reset_for_lazy_callable)
12547 0.051 0.000 0.051 0.000 {_codecs.utf_8_decode}
5946 0.028 0.000 0.037 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/identity.py:107(add)
5946 0.023 0.000 0.037 0.000 /usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/state.py:285(_reset)
17838 0.031 0.000 0.031 0.000 {method 'split' of 'str' objects}
2 0.018 0.009 0.029 0.014 /usr/local/lib/python2.7/dist-packages/sqlalchemy/util/_collections.py:687(unique_list)
5946 0.027 0.000 0.027 0.000 /usr/local/lib/python2.7/dist- packages/sqlalchemy/orm/state.py:44(__init__)
然而,我不需要这种情况发生。我不需要字符串是unicode格式,典型的ASCII或python“str”类型就可以了。我不知道如何摆脱它,或者为什么我需要它。我可能遗漏了什么
最后,有人能确认检索6k行所需的总时间(超过1秒)真的很慢吗?这对我来说似乎太长了,但我没有太多的依据。推动查询时间的主要因素是您获得了6000行。您真的需要所有6000行的所有列吗?解码时间不到总时间的1/5。试图对其进行微观优化可能是浪费时间。考虑需要移动的数据并让数据库执行繁重的工作可能是更好地利用时间。即使只抓取350行和一列,查询仍然非常慢,大约1/3秒。原始SQL查询将在0.01秒内捕获行。