Python 3.x peewee:如何将where子句添加到任何select中?
我有这样的模型:Python 3.x peewee:如何将where子句添加到任何select中?,python-3.x,peewee,Python 3.x,Peewee,我有这样的模型: class AbstractBaseModel(peewee.Model): uuid = peewee.UUIDField(default=uuid4) is_active = peewee.BooleanField(default=False) is_deleted = peewee.BooleanField(default=False) created_at = peewee.DateTimeField(default=datetime.n
class AbstractBaseModel(peewee.Model):
uuid = peewee.UUIDField(default=uuid4)
is_active = peewee.BooleanField(default=False)
is_deleted = peewee.BooleanField(default=False)
created_at = peewee.DateTimeField(default=datetime.now)
updated_at = peewee.DateTimeField(default=datetime.now)
deleted_at = peewee.DateTimeField(null=True)
class Meta:
abstract = True
indexes = (
(('is_active', 'is_deleted'), False),
)
posts = (
Post
.visible()
.select(Post.title)
.join(UserCTE, on=Post.user == UserCTE.c.id)
.with_cte(UserCTE)
)
for post in posts:
print(post.title)
我想:
处于活动状态==True
和处于删除状态==False的行
处于活动状态
和处于删除状态
标志这里有一个答案不是皮维所特有的 假设上面的(未命名)表是“thing”,那么本质上,您的模型擅长于像
select*fromthing
这样的查询
现在,定义一个相关视图,用于选择某些内容,选择您最喜欢的行子集:
sqlite> create view thing_v as
...> select uuid, created_at, updated_at, deleted_at
...> from thing
...> where is_active == True and is_deleted == False;
将模型指向该关系,该关系恰好是一个视图(命名查询)而不是一个表。它只是Python。。。将助手方法添加到模型类中。例如,如果我有一个博客帖子的
Post
类,我可能会写:
class Post(Model):
status = IntegerField() # 1=live, 2=draft, 3=deleted, e.g.
@classmethod
def visible(cls):
return cls.select().where(cls.status == 1)
然后,我可能会有一个所有已发布帖子的列表视图:
@app.route('/')
def post_index():
query = Post.visible().order_by(Post.timestamp.desc())
return render_template('post_index.html', query=query)
我想给出一个很好的答案。 对于连接和更复杂的查询,我们可以使用PeeWee功能,如下所示:
class BaseModel(peewee.Model):
is_deleted = peewee.BooleanField(default=False, index=True)
@classmethod
def visible_where_clause(cls):
return cls.is_deleted == False
@classmethod
def visible(cls):
return cls.select().where(cls.visible_where_clause())
@classmethod
def cte(cls, name=None):
if name is None:
name = 'CTE_{}'.format(cls.__name__)
return cls.visible().cte(name)
class Meta:
abstract = True
class User(BaseModel):
username = peewee.CharField(max_length=255, unique=True)
is_active = peewee.BooleanField(default=True, index=True)
@classmethod
def visible_where_clause(cls):
return (
(super().visible_where_clause()) & (cls.is_active == True)
)
UserCTE = User.cte()
class Post(BaseModel):
status = peewee.IntegerField() # 1=live, 2=draft, 3=deleted, e.g.
user = peewee.ForeignKeyField(User)
title = peewee.CharField(max_length=255)
@classmethod
def visible_where_clause(cls):
return (
(super().visible_where_clause()) & (cls.status == 1)
)
PostCTE = Post.cte()
然后,当我们只需要活动用户的活动帖子时,我们可以这样做:
class AbstractBaseModel(peewee.Model):
uuid = peewee.UUIDField(default=uuid4)
is_active = peewee.BooleanField(default=False)
is_deleted = peewee.BooleanField(default=False)
created_at = peewee.DateTimeField(default=datetime.now)
updated_at = peewee.DateTimeField(default=datetime.now)
deleted_at = peewee.DateTimeField(null=True)
class Meta:
abstract = True
indexes = (
(('is_active', 'is_deleted'), False),
)
posts = (
Post
.visible()
.select(Post.title)
.join(UserCTE, on=Post.user == UserCTE.c.id)
.with_cte(UserCTE)
)
for post in posts:
print(post.title)
记住
对于
CTE
对象,您必须通过添加.c.
来引用,并通过添加.with_CTE()
在查询结束时添加此CTE
。您知道如何将此应用于联接吗?祝贺您学习了CTE。这个答案肯定会弄乱局面,让通过谷歌来到这里的人感到相当困惑。你没有回答你的实际问题,而是谈论了一些相当高级的功能,写了很多无用的东西,让人不得不费力地去寻找真正的答案。@coleifer那么你能扩展你的答案以提供更灵活的解决方案吗?当您想在联接中使用视图或代理时,如何创建类似于视图或代理的模型?