为什么peewee强制将列选择为整数

Question

I can't use sqlite function group_concat() in peewee. Here is complete snipet. Somehow peewee want to convert result of group_concat() to integer, while it is string ("1,2"). I can't find the way to suppress it.

from peewee import *

db = SqliteDatabase(':memory:')

class Test(Model):
    name = CharField()
    score = IntegerField()

    class Meta:
        database = db

db.create_tables([Test])
Test.create(name='A', score=1).save()
Test.create(name='A', score=2).save()

#select name, group_concat(score) from Test group by name
for t in Test.select(Test.name, fn.group_concat(Test.score)).order_by(Test.name):
    pass

It produces following error:

Traceback (most recent call last):
File "C:\Users\u_tem0m\Dropbox\Wrk\sgo\broken.py", line 17, in <module>  
  for t in Test.select(Test.name, fn.group_concat(Test.score)).order_by(Test.name):  
File "C:\Program Files\Python 3.5\lib\site-packages\peewee.py", line 1938, in next
  obj = self.qrw.iterate()  
File "C:\Program Files\Python 3.5\lib\site-packages\peewee.py", line 1995, in iterate  
  return self.process_row(row)  
File "C:\Program Files\Python 3.5\lib\site-packages\peewee.py", line 2070, in process_row  
  setattr(instance, column, func(row[i]))  
File "C:\Program Files\Python 3.5\lib\site-packages\peewee.py", line 874, in python_value  
  return value if value is None else self.coerce(value)  
ValueError: invalid literal for int() with base 10: '1,2'  

Answer 1

Try adding a coerce(False) to your call to group_concat:

query = (Test
         .select(Test.name, fn.GROUP_CONCAT(Test.score).coerce(False))
         .order_by(Test.name))
for t in query:
    pass

Peewee sees that Test.score is an integer field, so whenever a function is called on that column, Peewee will try to convert the result back to an int. The problem is that group_concat returns a string, so we must tell Peewee not to mess with the return value.

Answer 2

Just found what result of fn.group_concat(""+Test.score) don't cast to integer. But I think resulting sql maybe less optimal

SELECT "t1"."name", group_concat(? + "t1"."score") AS allscore FROM "test" AS t1 ORDER BY "t1"."name" ['']

Do anybody knows more elegant way?