How to do 'or' when applying multiple values with the same lookup? - django-rest-framework

Question

By referring to this article, I was able to implement the method of and search.
Django-filter with DRF - How to do 'and' when applying multiple values with the same lookup?
I want to know how to do or search for multiple keywords using the same field. How can I implement it?
Here is the code:
from rest_framework import viewsets
from django_filters import rest_framework as filters
from .serializers import BookInfoSerializer
from .models import BookInfo
class MultiValueCharFilter(filters.BaseCSVFilter, filters.CharFilter):
def filter(self, qs, value):
# value is either a list or an 'empty' value
values = value or []
for value in values:
qs = super(MultiValueCharFilter, self).filter(qs, value)
return qs
class BookInfoFilter(filters.FilterSet):
title = MultiValueCharFilter(lookup_expr='contains')
# title = MultiValueCharFilter(lookup_expr='contains', conjoined=False) -> get an error
class Meta:
model = BookInfo
fields = ['title']
class BookInfoAPIView(viewsets.ReadOnlyModelViewSet):
queryset = BookInfo.objects.all()
serializer_class = BookInfoSerializer
filter_class = BookInfoFilter
if I set conjoined=False like this title = MultiValueCharFilter(lookup_expr='contains', conjoined=False) get an error __init__() got an unexpected keyword argument 'conjoined'
Django 3.2.5
django-filter 2.4.0
djangorestframework 3.12.4
Python 3.8.5

Answer 1

You can try to modify the queryset returned from MultiValueCharFilter
and combine values with operator.
example:
import operator
from functools import reduce
class MultiValueCharFilter(BaseCSVFilter, CharFilter):
def filter(self, qs, value):
expr = reduce(
operator.or_,
(Q(**{f'{self.field_name}__{self.lookup_expr}': v}) for v in value)
)
return qs.filter(expr)
class BookInfoFilter(filters.FilterSet):
title = MultiValueCharFilter(lookup_expr='contains')
class Meta:
model = BookInfo
fields = ['title']

Answer 2

You can try to create a new Class called ListFilter like this:
from django_filters.filters import Filter
from django_filters.conf import settings as django_filters_settings
from django.db.models.constants import LOOKUP_SEP
class ListFilter(Filter):
"""
Custom Filter for filtering multiple values.
"""
def __init__(self, query_param: str, *args, **kwargs):
"""
Override default variables.
Args:
query_param (str): Query param in URL
"""
super().__init__(*args, **kwargs)
self.query_param = query_param
self.distinct = True
def filter(self, qs, value):
"""
Override filter method in Filter class.
"""
try:
request = self.parent.request
values = request.query_params.getlist(self.query_param)
# Remove empty value in array
values = list(filter(None, values))
except AttributeError:
values = []
# Filter queryset by using OR expression when lookup_expr is 'in'
# Else filter queryset by using AND expression
if values and self.lookup_expr == 'in':
return super().filter(qs, values)
for value in set(values):
predicate = self.get_filter_predicate(value)
qs = self.get_method(qs)(**predicate)
return qs.distinct() if self.distinct else qs
def get_filter_predicate(self, value):
"""
This function helps to get predicate for filtering
"""
name = self.field_name
if (
name
and self.lookup_expr != django_filters_settings.DEFAULT_LOOKUP_EXPR
):
name = LOOKUP_SEP.join([name, self.lookup_expr])
return {name: value}
My class above supports filter nested fields using both OR and AND expressions. E.g. about filter title field using OR expression:
class BookInfoFilter(filters.FilterSet):
title = ListFilter(query_param='title')
class Meta:
model = BookInfo
fields = ['title']