python - 升级到 Peewee 2.6 后出现 sqlite3 InterfaceError

Question

从 v2.4.7 升级到 Peewee 2.6.3 后，迭代选择查询的结果时会弹出以下错误。

编辑:这似乎是与 create_or_get 方法的使用相关的错误。

 File "./script.py", line 137, in load_data
    for name,country in rows:
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/peewee.py", line 1957, in next
    obj = self.iterate()
  File "/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages/peewee.py", line 1934, in iterate
    row = self.cursor.fetchone()
sqlite3.InterfaceError: Cursor needed to be reset because of commit/rollback and can no longer be fetched from. 

这是有问题的代码:

for i in range(1, nb_rows // CHUNK_SIZE + 2):                                                                                                                                                                                                                                                                                                     
    rows = (Source.select(Source.name,Source.country)                                                                                                                       
           .where(Source.status == 'new').paginate(i, CHUNK_SIZE).tuples())                                                                                                     

    for name,country in rows:                                                                                                                                                                                                                                                                                                               
        person, created = Person.create_or_get(name = name, new = True)                                                                                                        

        if country:                                                                                                                                                                   
            country, created = Countries.create_or_get(name = country)                                                                                                                         
            Person_Country(person_id = person.id, country_id = country.id).save()   

您能帮我确定问题是什么以及如何解决它吗？

注意:使用Sqlite3 3.8.9

Answer 1

嗯，外部 SELECT 语句的游标仍然打开，因此通过使用外部 SELECT ，您应该可以让代码正常工作:

for i in range(1, nb_rows // CHUNK_SIZE + 2):                                                                                                                                                                                                                                                                                                     
    rows = (Source.select(Source.name,Source.country)                                                                                                                       
           .where(Source.status == 'new').paginate(i, CHUNK_SIZE).tuples())                                                                                                     

    # CONSUME SELECT
    rows = list(rows)

    for name,country in rows:                                                                                                                                                                                                                                                                                                               
        person, created = Person.create_or_get(name = name, new = True)                                                                                                        

        if country:                                                                                                                                                                   
            country, created = Countries.create_or_get(name = country)                                                                                                                         
            Person_Country(person_id = person.id, country_id = country.id).save()   

create_or_get 将使用事务(如果您已经处于事务中，则使用保存点)。当提交或回滚时，SELECT 的游标将无法再使用。