未插入Sqlalchemy查询参数

Question

我使用SQLAlchemy声明来处理MySQL。

from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relation, sessionmaker
import datetime

engine = create_engine('mysql+mysqldb://root:mypass@localhost/somedb')

Base = declarative_base()
Base.metadata.bind = engine
DBSession = sessionmaker(bind=engine)
session = DBSession()

class Item(Base):
    __tablename__ = 'item'
    id = Column(Integer, primary_key=True)
    dt = Column(DateTime)
    title = Column(UnicodeText)

Base.metadata.create_all(engine)

i = Item()
i.dt = datetime.datetime.now()
i.title = "hello world"
session.add(i)
session.commit()

此代码在session.commit()上抛出异常：

sqlalchemy.exc.ProgrammingError: (ProgrammingError) (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '%s, %s)' at line 1") b'INSERT INTO item (dt, title) VALUES (%s, %s)' (datetime.datetime(2014, 5, 16, 20, 58, 7, 729245), 'hello world')

异常的完整堆栈跟踪在帖子的末尾。

我发现参数没有正确插入查询字符串。有query = query.format( *db.literal(args) ) in the file MySQLdb/cursors.py, on the line 163行。 query变量是一个字符串。 string.format函数接受替换字段，例如{}，{1}，{23}，而不是%s。但查询变量中的替换字段为%s。

因此，参数未插入查询中。

我可以通过在sqlalchemy/sql/compiler.py文件变量BIND_TEMPLATES中进行更改来解决问题。我已将'format': "%%s"更改为'format': "{}"。

但我清楚地知道人们成功使用sqlalchemy没有这个错误。这个问题的真正原因是什么？也许我已经安装了一些不兼容的版本？

我在Windows 7 x64上使用Python 3.4， Mysql连接器：MySQL_python-1.2.3-py3.4-win-amd64.egg

异常的完整堆栈跟踪：

Traceback (most recent call last):
  File "C:\Program Files (x86)\JetBrains\PyCharm Community Edition 3.1.3\helpers\pydev\pydevd.py", line 1539, in <module>
    debugger.run(setup['file'], None, None)
  File "C:\Program Files (x86)\JetBrains\PyCharm Community Edition 3.1.3\helpers\pydev\pydevd.py", line 1150, in run
    pydev_imports.execfile(file, globals, locals) #execute the script
  File "C:\Program Files (x86)\JetBrains\PyCharm Community Edition 3.1.3\helpers\pydev\_pydev_execfile.py", line 37, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc) #execute the script
  File "C:/Work/midmay/midmay.parser/scripts/test.py", line 30, in <module>
    session.commit()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 765, in commit
    self.transaction.commit()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 370, in commit
    self._prepare_impl()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 350, in _prepare_impl
    self.session.flush()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 1903, in flush
    self._flush(objects)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 2021, in _flush
    transaction.rollback(_capture_exception=True)
  File "C:\Python34\lib\site-packages\sqlalchemy\util\langhelpers.py", line 57, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "C:\Python34\lib\site-packages\sqlalchemy\util\compat.py", line 168, in reraise
    raise value
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 1985, in _flush
    flush_context.execute()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\unitofwork.py", line 370, in execute
    rec.execute(self)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\unitofwork.py", line 523, in execute
    uow
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\persistence.py", line 64, in save_obj
    mapper, table, insert)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\persistence.py", line 594, in _emit_insert_statements
    execute(statement, params)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 720, in execute
    return meth(self, multiparams, params)
  File "C:\Python34\lib\site-packages\sqlalchemy\sql\elements.py", line 317, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 817, in _execute_clauseelement
    compiled_sql, distilled_params
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 947, in _execute_context
    context)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 1108, in _handle_dbapi_exception
    exc_info
  File "C:\Python34\lib\site-packages\sqlalchemy\util\compat.py", line 174, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=exc_value)
  File "C:\Python34\lib\site-packages\sqlalchemy\util\compat.py", line 167, in reraise
    raise value.with_traceback(tb)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\base.py", line 940, in _execute_context
    context)
  File "C:\Python34\lib\site-packages\sqlalchemy\engine\default.py", line 435, in do_execute
    cursor.execute(statement, parameters)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 184, in execute
    self.errorhandler(self, exc, value)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\connections.py", line 37, in defaulterrorhandler
    raise errorvalue
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 171, in execute
    r = self._query(query)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 330, in _query
    rowcount = self._do_query(q)
  File "C:\Python34\lib\site-packages\mysql_python-1.2.3-py3.4-win-amd64.egg\MySQLdb\cursors.py", line 294, in _do_query
    db.query(q)
sqlalchemy.exc.ProgrammingError: (ProgrammingError) (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '%s, %s)' at line 1") b'INSERT INTO item (dt, title) VALUES (%s, %s)' (datetime.datetime(2014, 5, 16, 20, 58, 7, 729245), 'hello world')

Answer 1

尝试添加__table_args__ = {}。这对我有用：

from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base, DeferredReflection
from sqlalchemy.orm import relation, relationship

DeclarativeBase = declarative_base(cls=DeferredReflection)

class MyItem(DeclarativeBase):
    __tablename__ = 'myitem'
    __table_args__ = {}

更新：我已经按原样运行你的代码（当然除了改变引擎的mysql url字符串之外）使用Python 2.7（x64，在Linux上）并且它运行没有任何问题（它创建了表并插入了'hello world'进去）。依赖关系：

MySQL-python==1.2.5
SQLAlchemy==0.9.2

更仔细地阅读你的帖子我发现你使用过Python 3.4。 http://docs.sqlalchemy.org/en/rel_0_9/changelog/migration_09.html州：

“所有SQLAlchemy模块和单元测试现在都可以很好地解决2.6前向的Python解释器，包括3.1和3.2解释器。”

这没有明确提及3.3和3.4。您可能在SA中遇到过一个错误，或者它还没有更新到3.4。我建议安装2.7（他们应能够在单个系统上共存），使用virtualenv for 2.7，安装deps并重新运行代码。

另一个可能的问题来源是3.4的MySQL驱动程序。我很伤心地说，但Python 3下*下MySQL的支持是严重缺乏：球队在我的工作中的驱动程序不仅漏水，但无法处理高负载下的许多连接。在修复驱动程序之前，最好使用2.7。那，或者只是改为Postgres作为db。

Answer 2

我找到了解决方案。也许它不是最好的，它并不适合所有人。但在这里。 解决方案是安装 Mysql Connector 而不是 MySQLDb ，并将连接字符串从mysql+mysqldb://root:mypass@localhost/somedb更改为mysql+connector://root:mypass@localhost/somedb。

如果您是Windows用户（就像我一样），并且您遇到此问题："Cannot open include file: 'config-win.h': No such file or directory" while installing mysql-python，那么您可以将Python版本从3.4降级到3.3并从此处下载预编译的Mysql Connector for python 3.3 ：http://dev.mysql.com/downloads/connector/python/

它对我有用。感谢。