如何使用Peewee查询几个类似的数据库? [英] How to query several similar databases using Peewee?

问题描述

我遇到了有关使用Peewee查询多个数据库的问题:

I'm stuck with a problem about querying multiple databases using Peewee:

• 我有2个现有的mysql数据库(我们分别命名为A和B)(结构类似，因为它是两个Bugzilla数据库)
• 我使用Pwiz生成模型(modelsA.py和modelsB.py)
• 我写这段代码:

.

from modelsA import *
from modelsB import *

问题是:由于modelsB中的类(有时)与modelsA相同，所以models B类会覆盖" models A类，从而无法查询A.

The problem is: as the classes in modelsB are (sometimes) the same than modelsA, modelsB classes "overwrite" modelsA classes, making impossible to query A.

此外，我不了解如何查询特定数据库之一. 例如，使用以下代码:

Besides, I don't understand how to query one of the specific database. For example, with this code:

c = Customers.get(Customers.customernumber == 12)

您如何知道要在哪个数据库上执行此查询?

How do you know on which database this query is gonna be executed?

我有一个主意，但对我来说似乎很肮脏: 我可以手动重命名来自modelsA.py和modelsB.py的类，以使其与众不同，然后编写以下代码:

I had an idea, but it seems dirty to me: I could manually rename classes from modelsA.py and modelsB.py to make them distincts and then write this code:

ca = CustomersA.get(CustomersA.customernumber == 12)
cb = CustomersB.get(CustomersB.customernumber == 12)

大致上，Peewee能够处理这类案件吗?如果是这样，该怎么办?片段将不胜感激^^ 谢谢.

Roughly, is Peewee able to deal with these kind of cases? If so, what is the way to do? Snippets would be very appreciated ^^ Thanks.

推荐答案

下一步可能无法完全解决您的问题，但是我自己尝试成功-正在使用 playhouse.Proxy 实例对于我要使用的每个架构，并在innerclass Meta中引用相应的代理.我想这也可以不用代理.但是，您似乎正在寻找跨模式查询，并且已经了解了我刚才提出的内容.

Next is maybe not exact an answer to your problem, but what I tried myself - succesfully - is using a playhouse.Proxy instance for every schema I want to use, and refer to a corresponding proxy in the innerclass Meta. I guess this will work without proxies too. However, seems you are looking for cross-schema queries, and already figured out what I came up with just now.

#!/usr/bin/python

import sqlite3
import peewee
from peewee import *
from playhouse.proxy import *

database_a_proxy = Proxy()
database_b_proxy = Proxy()

class BaseModelA(Model):
    class Meta:
            database = database_a_proxy

class BaseModelB(Model):
    class Meta:
            database = database_b_proxy

class RelationInSchemaA(BaseModelA):
    textfield = CharField()

class RelationInSchemaB(BaseModelB):
    textfield = CharField()

database_a = SqliteDatabase('schemaA', **{})
database_b = SqliteDatabase('schemaB', **{})

database_a_proxy.initialize(database_a)
database_b_proxy.initialize(database_b)

try:
   RelationInSchemaA.create_table()
   RelationInSchemaB.create_table()
except:
   pass

RelationInSchemaA.create(textfield='Hello')  
RelationInSchemaB.create(textfield='PeeWee')

好吧，这可以通过手工制作从pwiz.py生成的代码来实现.我敢肯定，也可以使用某种工厂采用一种更优雅，更懒惰 的方式(即不急于)来做到这一点，但是我没有花很多时间在Python和PeeWee上.如果是这样的话，我想pwiz.py也应该为此目的添加一个额外的标志.

Well, this is possible with handcrafting generated code from pwiz.py. I am sure there is a more elegant and lazy (i.e. not eager) way to do this, too, using some kind of factory, but I did not spend much time on Python nor PeeWee yet. If so, pwiz.py should have an extra flag for this purpose too, I guess.

这篇关于如何使用Peewee查询几个类似的数据库?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！