Django Regex Field Lookup - Sort by Number of Matches for Each Item in QuerySet

Question

I am experimenting with a basic regex expression as a way of performing a Django filter operation.

I would like to remove any insignificant words from a supplied query string, look for any objects with titles containing any of the remaining words, and then sort starting with those containing the most words.

Using a quick and simplified example:

ignored_words = {'for', 'a', 'of', 'the', 'and', 'to', 'in'}

keywords = []
for word in query.split():
    if word not in ignored_words:
        keywords.append(word)

if len(keywords) > 0:
    regex_str = r'(' + '|'.join(keywords) + ')'
    results = MyModel.objects.filter(title__iregex=regex_str)
    # Now sort them...

If my query string was 'Delicious Apples and Bananas' and I had three objects with the following titles:

• 'Apples'
• 'Bananas'
• 'Apples and Bananas'

is there an efficient way I can order my results by the number of keyword occurrences? More specifically, I'm not sure if I should be doing some sort of Count() operation whilst querying, or looping through the results afterwards and doing some sort of additional regex processing then.

Answer 1

In the end I performed a regex operation on the QuerySet after the filter.

def get_keyword_matches(query, regex):
    compiler = re.compile(regex)
    result = compiler.findall(query)
    return len(result)

results = sorted(results, key=lambda my_object: get_keyword_matches(my_object.title.lower(), regex_str), reverse=True)

If there's a more efficient way of doing this, however, I'd be keen to hear it.