Hmm, should I try with the dev mailing list? Guess it's something no one
faced before?
El martes, 14 de noviembre de 2017, 22:54:23 (UTC-3), Cristiano Coelho
escribió:
>
> I'm getting some very odd query when combining annotate with count. See
> the following:
>
> >>> q =
>> Vulnerability.objects.annotate(score=WordTrigramCustomSimilarity('test','summary'))
>> >>> q.count()
>> 3094
>> >>> print connection.queries[-1]
>> 'SELECT COUNT(*)
>> FROM (
>> SELECT "vulnerabilities_vulnerability"."id" AS Col1,
>> custom_word_similarity(\'test\', "vulnerabilities_vulnerability"."summary")
>> AS "score"
>> FROM "vulnerabilities_vulnerability"
>> GROUP BY "vulnerabilities_vulnerability"."id",
>> custom_word_similarity(\'test\', "vulnerabilities_vulnerability"."summary")
>> ) subquery
>> >>> q2 = Vulnerability.objects.filter(summary__icontains='test')
>> >>> q2.count()
>> 33
>> >>> print connection.queries[-1]
>> 'SELECT COUNT(*) AS "__count"
>> FROM "vulnerabilities_vulnerability"
>> WHERE UPPER("vulnerabilities_vulnerability"."summary"::text) LIKE
>> UPPER(\'%test%\')
>
>
>
> Custom function code, is this what's causing the odd count behavior? Did I
> miss anything?
>
> class WordTrigramCustomSimilarity(Func):
>> function = 'custom_word_similarity'
>> def __init__(self, string, expression, **extra):
>> if not hasattr(string, 'resolve_expression'):
>> string = Value(string)
>> super(WordTrigramCustomSimilarity, self).__init__(string,
>> expression, output_field=FloatField(), **extra)
>
>
> I would expect for the query to be a simple count, rather than a nested
> query with a useless group by (correct me if I'm wrong).
> The issue gets even worse if the function is expensive, since it gets
> called when it's not needed at all, more than once.
> Also the issue behaves pretty much the same if the queryset includes
> filtering and ordering but I didn't include it here for simplicity.
>
> Using Django 1.11.7 + postgres (psycopg) backend.
>
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