【发布时间】：2014-09-17 02:43:47
【问题描述】：
我是数据库新手，我正在尝试加快我在 Flask-SQLalchemy (Python 2.7) 应用程序中的查询速度。我已经分析了代码，但不知道如何解释它。我会喜欢关于这个主题的更一般的提示，但我的具体问题是：查询的“string_decoder”执行时间似乎非常昂贵，我假设它将字符串转换为 unicode，以便它可以以 unicode 格式返回它们。
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__)
但是，我不需要这种情况发生。我不需要字符串为 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，有人可以确认检索 6k 行所需的总时间（超过一秒）真的很慢吗？这对我来说似乎太长了，但我没有太多依据。
【问题讨论】：
标签： mysql sql python-2.7 unicode flask-sqlalchemy