python : sqlalchemy 批量插入 on_conflict_update

Question

我必须插入大约。我的 postgres 数据库每天 30000 行，我的数据库中有 4 列，即： id(pkey)、类别、创建日期、更新时间。我的要求是用今天的日期和新类别更新 updatedon 和类别列（如果 id 存在），否则 插入一个新行，createddate 和 updateon 相同.

我找到了 Ilja Everilä 的 [answer]: 进行批量更新

insert_statement = sqlalchemy.dialects.postgresql.insert(id_tag)
upsert_statement = insert_statement.on_conflict_do_update(
        constraint='id',
    set_={ "createddate": insert_statement.excluded.createddate }
)
insert_values = df.to_dict(orient='records')
conn.execute(upsert_statement, insert_values)

它抛出 AttributeError，

Traceback (most recent call last):

File "<ipython-input-60-4c5e5e0daf14>", line 5, in <module>
    set_= dict(createddate = insert_statement.excluded.createddate)

File "/home/bluepi/anaconda2/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 764, in __get__
    obj.__dict__[self.__name__] = result = self.fget(obj)

  File "/home/bluepi/anaconda2/lib/python2.7/site-packages/sqlalchemy/dialects/postgresql/dml.py", line 43, in excluded
    return alias(self.table, name='excluded').columns

  File "/home/bluepi/anaconda2/lib/python2.7/site-packages/sqlalchemy/sql/selectable.py", line 161, in alias
    return _interpret_as_from(selectable).alias(name=name, flat=flat)

AttributeError: 'TextClause' object has no attribute 'alias'

我已经按照此处所示尝试了一项一项的更新 http://docs.sqlalchemy.org/en/latest/dialects/postgresql.html#postgresql-insert-on-conflict，但我遇到了同样的错误。

请帮助我了解哪里出了问题，在此先感谢。

Answer 1

来自您的评论

id_tag is nothing but mane of my table in postgres

可以推断出 id_tag 绑定到一个字符串。如果您提供的 Minimal, Complete, and Verifiable example, there'd been a lot less guesswork. As it turns out, postgresql.dml.insert() automatically wraps passed strings in a text() construct, and the result when trying to use Insert.excluded 是：

In [2]: postgresql.insert('fail').excluded
~/sqlalchemy/lib/sqlalchemy/sql/selectable.py:43: SAWarning: Textual SQL FROM expression 'fail' should be explicitly declared as text('fail'), or use table('fail') for more specificity (this warning may be suppressed after 10 occurrences)
  {"expr": util.ellipses_string(element)})
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-f176aac8b913> in <module>()
----> 1 postgresql.insert('fail').excluded

~/sqlalchemy/lib/sqlalchemy/util/langhelpers.py in __get__(self, obj, cls)
    765         if obj is None:
    766             return self
--> 767         obj.__dict__[self.__name__] = result = self.fget(obj)
    768         return result
    769 

~/sqlalchemy/lib/sqlalchemy/dialects/postgresql/dml.py in excluded(self)
     41 
     42         """
---> 43         return alias(self.table, name='excluded').columns
     44 
     45     @_generative

~/sqlalchemy/lib/sqlalchemy/sql/selectable.py in alias(selectable, name, flat)
    159 
    160     """
--> 161     return _interpret_as_from(selectable).alias(name=name, flat=flat)
    162 
    163 

AttributeError: 'TextClause' object has no attribute 'alias'

因此，与其将包含 table 名称的字符串传递给 postgresql.dml.insert()，不如将其传递给实际的 Table object, or a light weight table() construct that has been populated with column() 对象。

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