问题:如何在Django中动态组成OR查询过滤器?
从一个示例中,您可以看到一个多重或查询过滤器:
Article.objects.filter(Q(pk=1) | Q(pk=2) | Q(pk=3))
例如,这导致:
[<Article: Hello>, <Article: Goodbye>, <Article: Hello and goodbye>]
但是,我想从列表中创建此查询过滤器。怎么做?
例如 [1, 2, 3] -> Article.objects.filter(Q(pk=1) | Q(pk=2) | Q(pk=3))
From an example you can see a multiple OR query filter:
Article.objects.filter(Q(pk=1) | Q(pk=2) | Q(pk=3))
For example, this results in:
[<Article: Hello>, <Article: Goodbye>, <Article: Hello and goodbye>]
However, I want to create this query filter from a list. How to do that?
e.g. [1, 2, 3] -> Article.objects.filter(Q(pk=1) | Q(pk=2) | Q(pk=3))
回答 0
您可以按以下方式链接查询:
values = [1,2,3]
# Turn list of values into list of Q objects
queries = [Q(pk=value) for value in values]
# Take one Q object from the list
query = queries.pop()
# Or the Q object with the ones remaining in the list
for item in queries:
query |= item
# Query the model
Article.objects.filter(query)
You could chain your queries as follows:
values = [1,2,3]
# Turn list of values into list of Q objects
queries = [Q(pk=value) for value in values]
# Take one Q object from the list
query = queries.pop()
# Or the Q object with the ones remaining in the list
for item in queries:
query |= item
# Query the model
Article.objects.filter(query)
回答 1
要构建更复杂的查询,还可以选择使用内置Q()对象的常量Q.OR和Q.AND以及add()方法,如下所示:
list = [1, 2, 3]
# it gets a bit more complicated if we want to dynamically build
# OR queries with dynamic/unknown db field keys, let's say with a list
# of db fields that can change like the following
# list_with_strings = ['dbfield1', 'dbfield2', 'dbfield3']
# init our q objects variable to use .add() on it
q_objects = Q(id__in=[])
# loop trough the list and create an OR condition for each item
for item in list:
q_objects.add(Q(pk=item), Q.OR)
# for our list_with_strings we can do the following
# q_objects.add(Q(**{item: 1}), Q.OR)
queryset = Article.objects.filter(q_objects)
# sometimes the following is helpful for debugging (returns the SQL statement)
# print queryset.query
To build more complex queries there is also the option to use built in Q() object’s constants Q.OR and Q.AND together with the add() method like so:
list = [1, 2, 3]
# it gets a bit more complicated if we want to dynamically build
# OR queries with dynamic/unknown db field keys, let's say with a list
# of db fields that can change like the following
# list_with_strings = ['dbfield1', 'dbfield2', 'dbfield3']
# init our q objects variable to use .add() on it
q_objects = Q(id__in=[])
# loop trough the list and create an OR condition for each item
for item in list:
q_objects.add(Q(pk=item), Q.OR)
# for our list_with_strings we can do the following
# q_objects.add(Q(**{item: 1}), Q.OR)
queryset = Article.objects.filter(q_objects)
# sometimes the following is helpful for debugging (returns the SQL statement)
# print queryset.query
回答 2
使用python的reduce函数编写Dave Webb答案的更短方法:
# For Python 3 only
from functools import reduce
values = [1,2,3]
# Turn list of values into one big Q objects
query = reduce(lambda q,value: q|Q(pk=value), values, Q())
# Query the model
Article.objects.filter(query)
A shorter way of writing Dave Webb’s answer using python’s reduce function:
# For Python 3 only
from functools import reduce
values = [1,2,3]
# Turn list of values into one big Q objects
query = reduce(lambda q,value: q|Q(pk=value), values, Q())
# Query the model
Article.objects.filter(query)
回答 3
from functools import reduce
from operator import or_
from django.db.models import Q
values = [1, 2, 3]
query = reduce(or_, (Q(pk=x) for x in values))
from functools import reduce
from operator import or_
from django.db.models import Q
values = [1, 2, 3]
query = reduce(or_, (Q(pk=x) for x in values))
回答 4
也许最好使用sql IN语句。
Article.objects.filter(id__in=[1, 2, 3])
请参阅queryset api参考。
如果您确实需要使用动态逻辑进行查询,则可以执行以下操作(丑陋且未经测试):
query = Q(field=1)
for cond in (2, 3):
query = query | Q(field=cond)
Article.objects.filter(query)
Maybe it’s better to use sql IN statement.
Article.objects.filter(id__in=[1, 2, 3])
See queryset api reference.
If you really need to make queries with dynamic logic, you can do something like this (ugly + not tested):
query = Q(field=1)
for cond in (2, 3):
query = query | Q(field=cond)
Article.objects.filter(query)
回答 5
见文档:
>>> Blog.objects.in_bulk([1])
{1: <Blog: Beatles Blog>}
>>> Blog.objects.in_bulk([1, 2])
{1: <Blog: Beatles Blog>, 2: <Blog: Cheddar Talk>}
>>> Blog.objects.in_bulk([])
{}
请注意,此方法仅适用于主键查找,但这似乎就是您要尝试的方法。
因此,您想要的是:
Article.objects.in_bulk([1, 2, 3])
See the docs:
>>> Blog.objects.in_bulk([1])
{1: <Blog: Beatles Blog>}
>>> Blog.objects.in_bulk([1, 2])
{1: <Blog: Beatles Blog>, 2: <Blog: Cheddar Talk>}
>>> Blog.objects.in_bulk([])
{}
Note that this method only works for primary key lookups, but that seems to be what you’re trying to do.
So what you want is:
Article.objects.in_bulk([1, 2, 3])
回答 6
如果我们要以编程方式设置要查询的数据库字段:
import operator
questions = [('question__contains', 'test'), ('question__gt', 23 )]
q_list = [Q(x) for x in questions]
Poll.objects.filter(reduce(operator.or_, q_list))
In case we want to programmatically set what db field we want to query:
import operator
questions = [('question__contains', 'test'), ('question__gt', 23 )]
q_list = [Q(x) for x in questions]
Poll.objects.filter(reduce(operator.or_, q_list))
回答 7
使用reduce
和or_
运算符按乘法字段进行过滤的解决方案。
from functools import reduce
from operator import or_
from django.db.models import Q
filters = {'field1': [1, 2], 'field2': ['value', 'other_value']}
qs = Article.objects.filter(
reduce(or_, (Q(**{f'{k}__in': v}) for k, v in filters.items()))
)
ps f
是一种新的格式字符串文字。它是在python 3.6中引入的
Solution which use reduce
and or_
operators to filter by multiply fields.
from functools import reduce
from operator import or_
from django.db.models import Q
filters = {'field1': [1, 2], 'field2': ['value', 'other_value']}
qs = Article.objects.filter(
reduce(or_, (Q(**{f'{k}__in': v}) for k, v in filters.items()))
)
p.s. f
is a new format strings literal. It was introduced in python 3.6
回答 8
您可以使用| =运算符来使用Q对象以编程方式更新查询。
You can use the |= operator to programmatically update a query using Q objects.
回答 9
这是动态pk列表:
pk_list = qs.values_list('pk', flat=True) # i.e [] or [1, 2, 3]
if len(pk_list) == 0:
Article.objects.none()
else:
q = None
for pk in pk_list:
if q is None:
q = Q(pk=pk)
else:
q = q | Q(pk=pk)
Article.objects.filter(q)
This one is for dynamic pk list:
pk_list = qs.values_list('pk', flat=True) # i.e [] or [1, 2, 3]
if len(pk_list) == 0:
Article.objects.none()
else:
q = None
for pk in pk_list:
if q is None:
q = Q(pk=pk)
else:
q = q | Q(pk=pk)
Article.objects.filter(q)
回答 10
另一种选择我是不知道的直到最近- QuerySet
还覆盖了&
,|
,~
,等运营商。OR Q对象的其他答案是对该问题的更好解决方案,但是出于兴趣/观点的考虑,您可以执行以下操作:
id_list = [1, 2, 3]
q = Article.objects.filter(pk=id_list[0])
for i in id_list[1:]:
q |= Article.objects.filter(pk=i)
str(q.query)
将返回一个查询,其中包含WHERE
子句中的所有过滤器。
Another option I wasn’t aware of until recently – QuerySet
also overrides the &
, |
, ~
, etc, operators. The other answers that OR Q objects are a better solution to this question, but for the sake of interest/argument, you can do:
id_list = [1, 2, 3]
q = Article.objects.filter(pk=id_list[0])
for i in id_list[1:]:
q |= Article.objects.filter(pk=i)
str(q.query)
will return one query with all the filters in the WHERE
clause.
回答 11
对于循环:
values = [1, 2, 3]
q = Q(pk__in=[]) # generic "always false" value
for val in values:
q |= Q(pk=val)
Article.objects.filter(q)
减少:
from functools import reduce
from operator import or_
values = [1, 2, 3]
q_objects = [Q(pk=val) for val in values]
q = reduce(or_, q_objects, Q(pk__in=[]))
Article.objects.filter(q)
这两个都相当于 Article.objects.filter(pk__in=values)
values
空着时要考虑什么很重要。许多Q()
以起始值开头的答案将返回所有内容。Q(pk__in=[])
是一个更好的起点。这是一个始终失败的Q对象,优化器可以很好地处理它(即使对于复杂的方程式)。
Article.objects.filter(Q(pk__in=[])) # doesn't hit DB
Article.objects.filter(Q(pk=None)) # hits DB and returns nothing
Article.objects.none() # doesn't hit DB
Article.objects.filter(Q()) # returns everything
如果要在values
为空时返回所有内容,则应进行AND操作~Q(pk__in=[])
以确保该行为:
values = []
q = Q()
for val in values:
q |= Q(pk=val)
Article.objects.filter(q) # everything
Article.objects.filter(q | author="Tolkien") # only Tolkien
q &= ~Q(pk__in=[])
Article.objects.filter(q) # everything
Article.objects.filter(q | author="Tolkien") # everything
重要的是要记住,什么都不Q()
是,不是一个总是成功的Q对象。涉及此操作的任何操作都会将其完全删除。
For loop:
values = [1, 2, 3]
q = Q(pk__in=[]) # generic "always false" value
for val in values:
q |= Q(pk=val)
Article.objects.filter(q)
Reduce:
from functools import reduce
from operator import or_
values = [1, 2, 3]
q_objects = [Q(pk=val) for val in values]
q = reduce(or_, q_objects, Q(pk__in=[]))
Article.objects.filter(q)
Both of these are equivalent to Article.objects.filter(pk__in=values)
It’s important to consider what you want when values
is empty. Many answers with Q()
as a starting value will return everything. Q(pk__in=[])
is a better starting value. It’s an always-failing Q object that’s handled nicely by the optimizer (even for complex equations).
Article.objects.filter(Q(pk__in=[])) # doesn't hit DB
Article.objects.filter(Q(pk=None)) # hits DB and returns nothing
Article.objects.none() # doesn't hit DB
Article.objects.filter(Q()) # returns everything
If you want to return everything when values
is empty, you should AND with ~Q(pk__in=[])
to ensure that behaviour:
values = []
q = Q()
for val in values:
q |= Q(pk=val)
Article.objects.filter(q) # everything
Article.objects.filter(q | author="Tolkien") # only Tolkien
q &= ~Q(pk__in=[])
Article.objects.filter(q) # everything
Article.objects.filter(q | author="Tolkien") # everything
It’s important to remember that Q()
is nothing, not an always-succeeding Q object. Any operation involving it will just drop it completely.
回答 12
easy ..
from django.db.models import Q import your model args =(Q(visibility = 1)|(Q(visibility = 0)&Q(user = self.user)))#元组参数= {} #dic顺序=’create_at’限制= 10
Models.objects.filter(*args,**parameters).order_by(order)[:limit]
easy..
from django.db.models import Q import you model args = (Q(visibility=1)|(Q(visibility=0)&Q(user=self.user))) #Tuple parameters={} #dic order = ‘create_at’ limit = 10
Models.objects.filter(*args,**parameters).order_by(order)[:limit]
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