英文:
Can I chain where clauses conditionally?
问题
在我的DAO API层中，我广泛使用Peewee作为ORM，并且需要在条件下使查询变得更窄，例如：
query = UserModel.select().where(UserModel.last_name == last_name)
if first_name is not None:
query = query.where(UserModel.first_name == first_name)
# ... 更多条件然后
df = pd.DataFrame(query.dicts())
这是在Peewee中以最符合惯例的方式进行条件查询窄化的方法吗？还有其他方法吗？这样做有什么优缺点吗？
英文:
I'm using Peewee as ORM extensively and within my DAO API layer I need to conditionally make a query narrower e.g.
query = UserModel.select().where(UserModel.last_name == last_name)
if first_name is not None:
query = query.where(UserModel.first_name == first_name)
# ... more conditions then
df = pd.DataFrame(query.dicts())
is this the most idiomatic way to conditionally make the queries narrower in Peewee or is there another way? Are there any pros and cons of doing this?
答案1
得分: 1
我建议首先处理动态条件，然后调用where子句。
query = UserModel.select()
filtered = UserModel.last_name == last_name
if first_name is not None:
filtered &= UserModel.first_name == first_name
# ... 更多条件接着写
# 如果有一些条件：
# filtered &= some_other_cond
# 如果有一些条件：
# filtered |= some_other_cond
# 根据您的函数逻辑选择其中之一
query = query.where(filtered)
df = pd.DataFrame(query.dicts())
英文:
I would suggest to doing first the dynamic condition and then calling where clause.
query = UserModel.select()
filtered = UserModel.last_name == last_name
if first_name is not None:
filtered &= UserModel.first_name == first_name
# ... more conditions then
# if some_cond:
# filtered &= some_other_cond
# if some_cond:
# filtered |= some_other_cond
# put one or other depending on
# the logic of your function
query = query.where(filtered)
df = pd.DataFrame(query.dicts())
Edit : fix an error in the code
答案2
得分: 1
Sure you can do this a couple ways:
# Chaining calls to .where() will AND the clauses together.
q = q.where(Model.field == 'something')
q = q.where(Model.other == 'another')
# Another option:
accum = []
accum.append(Model.field == 'something')
accum.append(Model.other == 'another')
q = q.where(*accum)
# Or you can explicitly AND them together:
q = q.where(reduce(operator.and_, accum))
Etc.
英文:
Sure you can do this a couple ways:
# Chaining calls to .where() will AND the clauses together.
q = q.where(Model.field == 'something')
q = q.where(Model.other == 'another')
# Another option:
accum = []
accum.append(Model.field == 'something')
accum.append(Model.other == 'another')
q = q.where(*accum)
# Or you can explicitly AND them together:
q = q.where(reduce(operator.and_, accum))
Etc.
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