5👍
How about using Django Q sets for this, so your filter would look like:
...objects.filter( Q(topic__exact = cat) | Q(topic__startswith = '%s,' % cat) | Q(topic__endswith = ',%s' % cat) | Q(topic__contains = ',%s,' % cat),
other_attributes = 'xxx',
3👍
MultiSelectField stores vales as a comma separated string in a CharField, so you basically want .topic__contains=topic
instead of .topic__in=topic
However, depending on your search form, you’ll want to join the conditions using different boolean operators to either narrow or widen the results. Depending on your needs, I would do one of the following:
- Use Q to build a complex query using
OR
joins (more complex, but more versatile) - Unpack named parameters from a dict into a
.filter()
(simpler, but constraining)
Dynamically build the query with Q.
This is the better method. It lets you use OR
, AND
, NOT
or XOR
in the query to refine search options.
# ...
search_params = Q()
# Let's say we have other search parameters also
search_params = search_params | Q(note__contains="example note")
if form.cleaned_data['topic']:
search_params = search_params | Q(topic__in=form.cleaned_data['topic'])
# ...
return qs.filter(search_params)
The resulting MYSQL query will look something like this:
SELECT * FROM `search_form`
WHERE (
`note` LIKE '%example note%' OR
`topic` LIKE '%about cats%'
)
Unpack named parameters from a dict
This method can only be used to narrow the search results using AND
in the query.
# ...
search_params = {}
# let's say there are other items in the query
search_params['note__contains'] = 'example note'
if form.cleaned_data['topic']:
search_params['topic__contains'] = form.cleaned_data['topic']
# ...
# unpack the search_params into the named parameters
return qs.filter(**search_params)
This will effectively build the Django query something like:
SearchForm.objects.filter(
note__contains="example note",
topic__contains="about cats"
)
The resulting database query will be something like:
SELECT * FROM `search_form`
WHERE (
`note` LIKE '%example note%' AND
`topic` LIKE '%about cats%'
)
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2👍
MultiSelectField is basically a CharField that stores the multiple choices values as a comma separated string.
Therefore you need a full table scan to perform this kind of QuerySet filtering on a MultiSelectField. You can use __regex field lookup to filter your QuerySet to match a given choice value:
(...)
searched_topics = form.cleaned_data['topic']
if searched_topics:
search_topic_regexp = "(^|,)%s(,|$)" % "|".join(searched_topics)
search_params.update({'topic__regex': search_topic_regexp})
(...)
For better performances (to avoid the full table scan on the topic field when you have a lot of Conversation entries), you should not use MultiSelectField but a ManyToMany relationship (that would use a separated join table).
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