python - sqlalchemy更新bindparam主键

Question

以下代码抛出“sqlalchemy.exc.CompileError:未使用的列名称:_id”。

User = Table('users', metadata,
 Column('id', Integer, primary_key=True),
 Column('score', Integer)
)

values = [
    {'score': 2, '_id': 1},
    {'score': 3, '_id': 3}
]
query = User.update().where(User.c.id == bindparam('_id')).values(score=bindparam('score'))
await db.execute_many(query, values)

db 是 databases 的实例.数据库。请注意，我必须使用名称“_id”，因为 SQLalchemy 说“id”是保留的。

除了单独更新每一行之外还有其他解决方案吗？

Answer 1

Database.execute_many()来电 Connection.execute_many()它将您的查询分解为单独的查询( values 中的每个元素一个)，方法如下( source ):

    async def execute_many(
        self, query: typing.Union[ClauseElement, str], values: list
    ) -> None:
        queries = [self._build_query(query, values_set) for values_set in values]
        async with self._query_lock:
            await self._connection.execute_many(queries)

请注意，它调用 _build_query()方法(source):

    @staticmethod
    def _build_query(
        query: typing.Union[ClauseElement, str], values: dict = None
    ) -> ClauseElement:
        if isinstance(query, str):
            query = text(query)

            return query.bindparams(**values) if values is not None else query
        elif values:
            return query.values(**values)

        return query

因为您没有通过 str查询并且您正在传递值，控制输入 elif values:条件处理，其中值的各个字典被解包到 .values() 中查询的方法(即 Update.values() )。这基本上使得它试图编译的查询是这样的:

query = (
    User.update()
    .where(User.c.id == bindparam("_id"))
    .values(score=bindparam("score"))
    .values(score=2, _id=1)
)

第二个值子句会产生一个新的更新，其中包含新的绑定(bind)参数，这些参数试图为 score 设置值。和_id 。这会导致查询编译失败，因为没有 _id表格上的列。

所以重现错误的 MCVE 实际上是这样的:

from sqlalchemy.dialects import postgresql

User.update().values(score=2, _id=1).compile(dialect=postgresql.dialect())

加薪:

Traceback (most recent call last):
  File ".\main.py", line 31, in <module>
    User.update().values(score=2, _id=1).compile(dialect=postgresql.dialect())
  File "<string>", line 1, in <lambda>
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\elements.py", line 462, in compile
    return self._compiler(dialect, bind=bind, **kw)
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\elements.py", line 468, in _compiler
    return dialect.statement_compiler(dialect, self, **kw)
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\compiler.py", line 571, in __init__
    Compiled.__init__(self, dialect, statement, **kwargs)
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\compiler.py", line 319, in __init__
    self.string = self.process(self.statement, **compile_kwargs)
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\compiler.py", line 350, in process
    return obj._compiler_dispatch(self, **kwargs)
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\visitors.py", line 92, in _compiler_dispatch
    return meth(self, **kw)
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\compiler.py", line 2569, in visit_update
    self, update_stmt, crud.ISUPDATE, **kw
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\crud.py", line 62, in _setup_crud_params
    return _get_crud_params(compiler, stmt, **kw)
  File "C:\Users\peter\Documents\git\stackoverflow\58668615-sqalchemy-update-bindparam-primary-key\.venv\lib\site-packages\sqlalchemy\sql\crud.py", line 177, in _get_crud_params
    % (", ".join("%s" % c for c in check))
sqlalchemy.exc.CompileError: Unconsumed column names: _id

为了总结这个问题，您构建了一个查询，并将绑定(bind)参数传递给 Update.where()和Update.values() 。然后，您将该查询和您的值传递给 Database.execute_many()他们将值列表中的各个元素解压到第二次调用 Update.values() 中。在您的查询中，将您的查询替换为尝试为 _id 设置值的查询不存在的列。

Is there any solution other than updating each row individullay?

使用 sqlalchemy 引擎和查询时，查询工作得很好:

# using a sqlalchemy engine
engine.execute(query, values)

否则，应该有效的是将查询作为字符串发送到 Database.execute_many()因为这意味着查询将在 if isinstance(query, str): 中处理_build_query()的一部分将避免第二个 .values() 的方法对查询进行的调用:

db.execute_many(str(query), values)