Re: Strange query when using annotate and count
Update. Found a work around that gets rid of the unnecessary group by (and
hence speeds up the query, from ~200ms to ~100ms in my use case). Simply
adding a .values('pk').
Bad thing, every model needs a custom manager and it will still use an
inner query, still trying to figure out the side effects of it, nothing so
far...
class FasterCountQuerySet(QuerySet):
> def count(self):
> return super(FasterCountQuerySet, self.values('pk')).count()
>
Makes me wonder if the original count code can be made "smarter" in order
to prevent the unnecessary group by, or if this simply a bug
El miércoles, 6 de diciembre de 2017, 10:28:22 (UTC-3), Cristiano Coelho
escribió:
>
> After testing for a while, there really doesn't seem to be a good way to
> do this. .
>
> Annotation is required since the query is filtered based on the annotated
> value, so any attempt to clear annotations would fail. Although a lookup
> could be used for the filtering.
> But a custom lookup is not possible since the query also sorts by the
> annotated value, so an annotation is required.
>
> This means that I would need to use a custom lookup for count queries, and
> annotation for result queries, which would mean a lot of duplicated code
> and also that the Django Paginator class can't be used since it expects
> only one queryset.
>
>
> Are there really no options to make a count with a custom function to skip
> the group by clause (and so the inner query)? I mean there's no group by at
> all with the original query, it's just when count is used.
>
> To summarize, the original query is a bit more complex than the one
> described on top, reason annotate is needed, and it looks more like:
>
> q =
> Vulnerability.objects.annotate(score=WordTrigramCustomSimilarity('test','summary')).filter(score__gt=0.6).order_by('-score')
>
> Which is then sent to a paginator, that ends up almost adding 3 times more
> database query time do to the horrid count query generated.
>
>
> El viernes, 24 de noviembre de 2017, 18:04:21 (UTC-3), Cristiano Coelho
> escribió:
>>
>> Hello Simon,
>>
>> You are right, the score is really not meant to be attached so a custom
>> lookup might work, if it wasn't for the issue that an order_by clause would
>> fail without the annotation.
>>
>> So it seems it's either update and duplicate a lot of code or find a very
>> ugly work around, I was hoping I missed some flag or implementation detail
>> on the custom function to tell the query builder to avoid all the grouping
>> and subquery stuff, will research more...
>>
>>
>> El viernes, 24 de noviembre de 2017, 14:39:27 (UTC-3), Simon Charette
>> escribió:
>>>
>>> Hello Cristiano,
>>>
>>> If you are solely using this annotation for querying purpose, that means
>>> you are
>>> not expecting a `score` attribute to be attached to your `Vulnerability`
>>> instances,
>>> you could try defining your function as a lookup on CharField/TextField
>>> instead.
>>>
>>> You could then use it only when required by passing a tuple of values to
>>> it.
>>>
>>> e.g.
>>>
>>> Vulnerability.objects.filter(summary__wordsimilarity_gt=('test',
>>> threshold))
>>>
>>> If you need the value annotated I'm afraid the best solution would be to
>>> use
>>> a custom paginator class. You could give a try at detecting whether or
>>> not
>>> an annotation is referenced before removing it from query.annotations and
>>> report your finding on the aforementioned ticket but I expect this to be
>>> relatively hard to do correctly. Still it would make implementing
>>> `alias()`
>>> way easier and provide help for users in the situation as you.
>>>
>>> Best,
>>> Simon
>>>
>>> Le vendredi 24 novembre 2017 08:14:10 UTC-5, Cristiano Coelho a écrit :
Hello Simon,
That private API is good to know, but now that I think of it would
still not work for me, since my queryset is passed to a paginator and
that's the class that does both the count and actual queryset execution,
so
need a queryset that can have both the annotation but also clears it if
count is called so it doesn't create the redundant sub queries.
I'm wondering what's better, should I try to resolve this at the
manager level overriding count? I feel like this might cause issues if the
annotation is actually legit (ie with an aggregate) and it needs the
subquery after all.
The other option is to subclass the paginator class with a special one
that does this annotation clearing before running count.
Even with these cases, if the annotated value is used later with a
filter query I can't really simply removed, but the sub queries and extra
function calls really doesn't make sense to be there when doing a count,
so
it seems that all the options are quite bad and hackish.
Any other options?
El viernes, 24 de noviembre de 2017, 1:12:07 (UTC-3), Simon Charette
escribió:
>
Re: Strange query when using annotate and count
After testing for a while, there really doesn't seem to be a good way to do
this. .
Annotation is required since the query is filtered based on the annotated
value, so any attempt to clear annotations would fail. Although a lookup
could be used for the filtering.
But a custom lookup is not possible since the query also sorts by the
annotated value, so an annotation is required.
This means that I would need to use a custom lookup for count queries, and
annotation for result queries, which would mean a lot of duplicated code
and also that the Django Paginator class can't be used since it expects
only one queryset.
Are there really no options to make a count with a custom function to skip
the group by clause (and so the inner query)? I mean there's no group by at
all with the original query, it's just when count is used.
To summarize, the original query is a bit more complex than the one
described on top, reason annotate is needed, and it looks more like:
q =
Vulnerability.objects.annotate(score=WordTrigramCustomSimilarity('test','summary')).filter(score__gt=0.6).order_by('-score')
Which is then sent to a paginator, that ends up almost adding 3 times more
database query time do to the horrid count query generated.
El viernes, 24 de noviembre de 2017, 18:04:21 (UTC-3), Cristiano Coelho
escribió:
>
> Hello Simon,
>
> You are right, the score is really not meant to be attached so a custom
> lookup might work, if it wasn't for the issue that an order_by clause would
> fail without the annotation.
>
> So it seems it's either update and duplicate a lot of code or find a very
> ugly work around, I was hoping I missed some flag or implementation detail
> on the custom function to tell the query builder to avoid all the grouping
> and subquery stuff, will research more...
>
>
> El viernes, 24 de noviembre de 2017, 14:39:27 (UTC-3), Simon Charette
> escribió:
>>
>> Hello Cristiano,
>>
>> If you are solely using this annotation for querying purpose, that means
>> you are
>> not expecting a `score` attribute to be attached to your `Vulnerability`
>> instances,
>> you could try defining your function as a lookup on CharField/TextField
>> instead.
>>
>> You could then use it only when required by passing a tuple of values to
>> it.
>>
>> e.g.
>>
>> Vulnerability.objects.filter(summary__wordsimilarity_gt=('test',
>> threshold))
>>
>> If you need the value annotated I'm afraid the best solution would be to
>> use
>> a custom paginator class. You could give a try at detecting whether or not
>> an annotation is referenced before removing it from query.annotations and
>> report your finding on the aforementioned ticket but I expect this to be
>> relatively hard to do correctly. Still it would make implementing
>> `alias()`
>> way easier and provide help for users in the situation as you.
>>
>> Best,
>> Simon
>>
>> Le vendredi 24 novembre 2017 08:14:10 UTC-5, Cristiano Coelho a écrit :
>>>
>>> Hello Simon,
>>>
>>> That private API is good to know, but now that I think of it would still
>>> not work for me, since my queryset is passed to a paginator and that's the
>>> class that does both the count and actual queryset execution, so need a
>>> queryset that can have both the annotation but also clears it if count is
>>> called so it doesn't create the redundant sub queries.
>>>
>>> I'm wondering what's better, should I try to resolve this at the manager
>>> level overriding count? I feel like this might cause issues if the
>>> annotation is actually legit (ie with an aggregate) and it needs the
>>> subquery after all.
>>> The other option is to subclass the paginator class with a special one
>>> that does this annotation clearing before running count.
>>>
>>> Even with these cases, if the annotated value is used later with a
>>> filter query I can't really simply removed, but the sub queries and extra
>>> function calls really doesn't make sense to be there when doing a count, so
>>> it seems that all the options are quite bad and hackish.
>>>
>>> Any other options?
>>>
>>>
>>> El viernes, 24 de noviembre de 2017, 1:12:07 (UTC-3), Simon Charette
>>> escribió:
Hello Cristiano,
> Isn't there a way (even if it's hackish) to simply clear the
annotations (and order by)? I know querysets are smart enough to not
include the order by clause if there's a count.
The ordering is cleared on `count()` because it shouldn't interfere
with the result in any way. You can clear annotations using
`queryset.query.annotations.clear()` but be aware that it is a private API
that could change under your feet. Make sure to make a copy of the
queryset
(e.g. copy = queryset.all()) before performing this change as it will
alter
the queryset in place.
Best,
Simon
Le jeudi 23 novembre 2017 22:41:41 UTC-5, Cristiano Coelho a écrit :
>
> Hello Simon, thanks for the response.
>
> The above
Re: Strange query when using annotate and count
Hello Simon,
You are right, the score is really not meant to be attached so a custom
lookup might work, if it wasn't for the issue that an order_by clause would
fail without the annotation.
So it seems it's either update and duplicate a lot of code or find a very
ugly work around, I was hoping I missed some flag or implementation detail
on the custom function to tell the query builder to avoid all the grouping
and subquery stuff, will research more...
El viernes, 24 de noviembre de 2017, 14:39:27 (UTC-3), Simon Charette
escribió:
>
> Hello Cristiano,
>
> If you are solely using this annotation for querying purpose, that means
> you are
> not expecting a `score` attribute to be attached to your `Vulnerability`
> instances,
> you could try defining your function as a lookup on CharField/TextField
> instead.
>
> You could then use it only when required by passing a tuple of values to
> it.
>
> e.g.
>
> Vulnerability.objects.filter(summary__wordsimilarity_gt=('test',
> threshold))
>
> If you need the value annotated I'm afraid the best solution would be to
> use
> a custom paginator class. You could give a try at detecting whether or not
> an annotation is referenced before removing it from query.annotations and
> report your finding on the aforementioned ticket but I expect this to be
> relatively hard to do correctly. Still it would make implementing `alias()`
> way easier and provide help for users in the situation as you.
>
> Best,
> Simon
>
> Le vendredi 24 novembre 2017 08:14:10 UTC-5, Cristiano Coelho a écrit :
>>
>> Hello Simon,
>>
>> That private API is good to know, but now that I think of it would still
>> not work for me, since my queryset is passed to a paginator and that's the
>> class that does both the count and actual queryset execution, so need a
>> queryset that can have both the annotation but also clears it if count is
>> called so it doesn't create the redundant sub queries.
>>
>> I'm wondering what's better, should I try to resolve this at the manager
>> level overriding count? I feel like this might cause issues if the
>> annotation is actually legit (ie with an aggregate) and it needs the
>> subquery after all.
>> The other option is to subclass the paginator class with a special one
>> that does this annotation clearing before running count.
>>
>> Even with these cases, if the annotated value is used later with a filter
>> query I can't really simply removed, but the sub queries and extra function
>> calls really doesn't make sense to be there when doing a count, so it seems
>> that all the options are quite bad and hackish.
>>
>> Any other options?
>>
>>
>> El viernes, 24 de noviembre de 2017, 1:12:07 (UTC-3), Simon Charette
>> escribió:
>>>
>>> Hello Cristiano,
>>>
>>> > Isn't there a way (even if it's hackish) to simply clear the
>>> annotations (and order by)? I know querysets are smart enough to not
>>> include the order by clause if there's a count.
>>>
>>> The ordering is cleared on `count()` because it shouldn't interfere with
>>> the result in any way. You can clear annotations using
>>> `queryset.query.annotations.clear()` but be aware that it is a private API
>>> that could change under your feet. Make sure to make a copy of the queryset
>>> (e.g. copy = queryset.all()) before performing this change as it will alter
>>> the queryset in place.
>>>
>>> Best,
>>> Simon
>>>
>>> Le jeudi 23 novembre 2017 22:41:41 UTC-5, Cristiano Coelho a écrit :
Hello Simon, thanks for the response.
The above code is just an example, the reason behind the annotate
because there's some complicated code that builds a queryset and annotates
it so it can easily be reused. It works fine 99% of the time except when
there's a count involved and it ends up being redundant. The solution
would
be to not annotate anything and replace the code in multiple places to add
the annotate call (or similar using a custom queryset or manager I guess),
but that's quite painful and will end up with a lot of duplicated code
since there's also an order_by that follows the annotate that needs to be
moved over as well
Isn't there a way (even if it's hackish) to simply clear the
annotations (and order by)? I know querysets are smart enough to not
include the order by clause if there's a count.
You could also suggest using two separate calls or a flag to pass down
to the internal code so it doesn't include the additional stuff, but that
wouldn't work since paginators accept only one query set for example and
internall uses it for both count and results.
El viernes, 24 de noviembre de 2017, 0:05:29 (UTC-3), Simon Charette
escribió:
>
> Hello Cristiano,
>
> I understand your frustration but please avoid using the developer
> mailing list
> as a second tier support channel. I suggest you try the IRC #django
>
Re: Strange query when using annotate and count
Hello Cristiano,
If you are solely using this annotation for querying purpose, that means
you are
not expecting a `score` attribute to be attached to your `Vulnerability`
instances,
you could try defining your function as a lookup on CharField/TextField
instead.
You could then use it only when required by passing a tuple of values to it.
e.g.
Vulnerability.objects.filter(summary__wordsimilarity_gt=('test', threshold))
If you need the value annotated I'm afraid the best solution would be to use
a custom paginator class. You could give a try at detecting whether or not
an annotation is referenced before removing it from query.annotations and
report your finding on the aforementioned ticket but I expect this to be
relatively hard to do correctly. Still it would make implementing `alias()`
way easier and provide help for users in the situation as you.
Best,
Simon
Le vendredi 24 novembre 2017 08:14:10 UTC-5, Cristiano Coelho a écrit :
>
> Hello Simon,
>
> That private API is good to know, but now that I think of it would still
> not work for me, since my queryset is passed to a paginator and that's the
> class that does both the count and actual queryset execution, so need a
> queryset that can have both the annotation but also clears it if count is
> called so it doesn't create the redundant sub queries.
>
> I'm wondering what's better, should I try to resolve this at the manager
> level overriding count? I feel like this might cause issues if the
> annotation is actually legit (ie with an aggregate) and it needs the
> subquery after all.
> The other option is to subclass the paginator class with a special one
> that does this annotation clearing before running count.
>
> Even with these cases, if the annotated value is used later with a filter
> query I can't really simply removed, but the sub queries and extra function
> calls really doesn't make sense to be there when doing a count, so it seems
> that all the options are quite bad and hackish.
>
> Any other options?
>
>
> El viernes, 24 de noviembre de 2017, 1:12:07 (UTC-3), Simon Charette
> escribió:
>>
>> Hello Cristiano,
>>
>> > Isn't there a way (even if it's hackish) to simply clear the
>> annotations (and order by)? I know querysets are smart enough to not
>> include the order by clause if there's a count.
>>
>> The ordering is cleared on `count()` because it shouldn't interfere with
>> the result in any way. You can clear annotations using
>> `queryset.query.annotations.clear()` but be aware that it is a private API
>> that could change under your feet. Make sure to make a copy of the queryset
>> (e.g. copy = queryset.all()) before performing this change as it will alter
>> the queryset in place.
>>
>> Best,
>> Simon
>>
>> Le jeudi 23 novembre 2017 22:41:41 UTC-5, Cristiano Coelho a écrit :
>>>
>>> Hello Simon, thanks for the response.
>>>
>>> The above code is just an example, the reason behind the annotate
>>> because there's some complicated code that builds a queryset and annotates
>>> it so it can easily be reused. It works fine 99% of the time except when
>>> there's a count involved and it ends up being redundant. The solution would
>>> be to not annotate anything and replace the code in multiple places to add
>>> the annotate call (or similar using a custom queryset or manager I guess),
>>> but that's quite painful and will end up with a lot of duplicated code
>>> since there's also an order_by that follows the annotate that needs to be
>>> moved over as well
>>>
>>> Isn't there a way (even if it's hackish) to simply clear the annotations
>>> (and order by)? I know querysets are smart enough to not include the order
>>> by clause if there's a count.
>>>
>>> You could also suggest using two separate calls or a flag to pass down
>>> to the internal code so it doesn't include the additional stuff, but that
>>> wouldn't work since paginators accept only one query set for example and
>>> internall uses it for both count and results.
>>>
>>>
>>>
>>> El viernes, 24 de noviembre de 2017, 0:05:29 (UTC-3), Simon Charette
>>> escribió:
Hello Cristiano,
I understand your frustration but please avoid using the developer
mailing list
as a second tier support channel. I suggest you try the IRC #django
channel if
you need to want to get faster support.
What's happening here is that annotate() really means "select this
field" while
in your other case you use a lookup (summary__icontains) which are only
going to
be added to the WHERE clause of your query.
I'm not sure why you are annotating your queryset without referring to
it in
a filter clause later on but the ORM cannot simply ignore it when you
are
performing your `count()` because some annotations could interfere with
grouping
somehow.
There is an open ticket[0] to add support for an `alias()` method that
would
allow the
Re: Strange query when using annotate and count
Hello Simon,
That private API is good to know, but now that I think of it would still
not work for me, since my queryset is passed to a paginator and that's the
class that does both the count and actual queryset execution, so need a
queryset that can have both the annotation but also clears it if count is
called so it doesn't create the redundant sub queries.
I'm wondering what's better, should I try to resolve this at the manager
level overriding count? I feel like this might cause issues if the
annotation is actually legit (ie with an aggregate) and it needs the
subquery after all.
The other option is to subclass the paginator class with a special one that
does this annotation clearing before running count.
Even with these cases, if the annotated value is used later with a filter
query I can't really simply removed, but the sub queries and extra function
calls really doesn't make sense to be there when doing a count, so it seems
that all the options are quite bad and hackish.
Any other options?
El viernes, 24 de noviembre de 2017, 1:12:07 (UTC-3), Simon Charette
escribió:
>
> Hello Cristiano,
>
> > Isn't there a way (even if it's hackish) to simply clear the annotations
> (and order by)? I know querysets are smart enough to not include the order
> by clause if there's a count.
>
> The ordering is cleared on `count()` because it shouldn't interfere with
> the result in any way. You can clear annotations using
> `queryset.query.annotations.clear()` but be aware that it is a private API
> that could change under your feet. Make sure to make a copy of the queryset
> (e.g. copy = queryset.all()) before performing this change as it will alter
> the queryset in place.
>
> Best,
> Simon
>
> Le jeudi 23 novembre 2017 22:41:41 UTC-5, Cristiano Coelho a écrit :
>>
>> Hello Simon, thanks for the response.
>>
>> The above code is just an example, the reason behind the annotate because
>> there's some complicated code that builds a queryset and annotates it so it
>> can easily be reused. It works fine 99% of the time except when there's a
>> count involved and it ends up being redundant. The solution would be to not
>> annotate anything and replace the code in multiple places to add the
>> annotate call (or similar using a custom queryset or manager I guess), but
>> that's quite painful and will end up with a lot of duplicated code since
>> there's also an order_by that follows the annotate that needs to be moved
>> over as well
>>
>> Isn't there a way (even if it's hackish) to simply clear the annotations
>> (and order by)? I know querysets are smart enough to not include the order
>> by clause if there's a count.
>>
>> You could also suggest using two separate calls or a flag to pass down to
>> the internal code so it doesn't include the additional stuff, but that
>> wouldn't work since paginators accept only one query set for example and
>> internall uses it for both count and results.
>>
>>
>>
>> El viernes, 24 de noviembre de 2017, 0:05:29 (UTC-3), Simon Charette
>> escribió:
>>>
>>> Hello Cristiano,
>>>
>>> I understand your frustration but please avoid using the developer
>>> mailing list
>>> as a second tier support channel. I suggest you try the IRC #django
>>> channel if
>>> you need to want to get faster support.
>>>
>>> What's happening here is that annotate() really means "select this
>>> field" while
>>> in your other case you use a lookup (summary__icontains) which are only
>>> going to
>>> be added to the WHERE clause of your query.
>>>
>>> I'm not sure why you are annotating your queryset without referring to
>>> it in
>>> a filter clause later on but the ORM cannot simply ignore it when you are
>>> performing your `count()` because some annotations could interfere with
>>> grouping
>>> somehow.
>>>
>>> There is an open ticket[0] to add support for an `alias()` method that
>>> would
>>> allow the ORM to clear/ignore the specified expressions if it's not
>>> referenced
>>> in the query.
>>>
>>> In the mean time I think the best approach would be to avoid annotating
>>> the
>>> queryset if your don't need to reference the score.
>>>
>>> Cheers,
>>> Simon
>>>
>>> [0] https://code.djangoproject.com/ticket/27719
>>>
>>> Le mardi 21 novembre 2017 08:46:21 UTC-5, Cristiano Coelho a écrit :
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\',
>>
Re: Strange query when using annotate and count
Hello Cristiano,
> Isn't there a way (even if it's hackish) to simply clear the annotations
(and order by)? I know querysets are smart enough to not include the order
by clause if there's a count.
The ordering is cleared on `count()` because it shouldn't interfere with
the result in any way. You can clear annotations using
`queryset.query.annotations.clear()` but be aware that it is a private API
that could change under your feet. Make sure to make a copy of the queryset
(e.g. copy = queryset.all()) before performing this change as it will alter
the queryset in place.
Best,
Simon
Le jeudi 23 novembre 2017 22:41:41 UTC-5, Cristiano Coelho a écrit :
>
> Hello Simon, thanks for the response.
>
> The above code is just an example, the reason behind the annotate because
> there's some complicated code that builds a queryset and annotates it so it
> can easily be reused. It works fine 99% of the time except when there's a
> count involved and it ends up being redundant. The solution would be to not
> annotate anything and replace the code in multiple places to add the
> annotate call (or similar using a custom queryset or manager I guess), but
> that's quite painful and will end up with a lot of duplicated code since
> there's also an order_by that follows the annotate that needs to be moved
> over as well
>
> Isn't there a way (even if it's hackish) to simply clear the annotations
> (and order by)? I know querysets are smart enough to not include the order
> by clause if there's a count.
>
> You could also suggest using two separate calls or a flag to pass down to
> the internal code so it doesn't include the additional stuff, but that
> wouldn't work since paginators accept only one query set for example and
> internall uses it for both count and results.
>
>
>
> El viernes, 24 de noviembre de 2017, 0:05:29 (UTC-3), Simon Charette
> escribió:
>>
>> Hello Cristiano,
>>
>> I understand your frustration but please avoid using the developer
>> mailing list
>> as a second tier support channel. I suggest you try the IRC #django
>> channel if
>> you need to want to get faster support.
>>
>> What's happening here is that annotate() really means "select this field"
>> while
>> in your other case you use a lookup (summary__icontains) which are only
>> going to
>> be added to the WHERE clause of your query.
>>
>> I'm not sure why you are annotating your queryset without referring to it
>> in
>> a filter clause later on but the ORM cannot simply ignore it when you are
>> performing your `count()` because some annotations could interfere with
>> grouping
>> somehow.
>>
>> There is an open ticket[0] to add support for an `alias()` method that
>> would
>> allow the ORM to clear/ignore the specified expressions if it's not
>> referenced
>> in the query.
>>
>> In the mean time I think the best approach would be to avoid annotating
>> the
>> queryset if your don't need to reference the score.
>>
>> Cheers,
>> Simon
>>
>> [0] https://code.djangoproject.com/ticket/27719
>>
>> Le mardi 21 novembre 2017 08:46:21 UTC-5, Cristiano Coelho a écrit :
>>>
>>> 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
Re: Strange query when using annotate and count
Hello Simon, thanks for the response.
The above code is just an example, the reason behind the annotate because
there's some complicated code that builds a queryset and annotates it so it
can easily be reused. It works fine 99% of the time except when there's a
count involved and it ends up being redundant. The solution would be to not
annotate anything and replace the code in multiple places to add the
annotate call (or similar using a custom queryset or manager I guess), but
that's quite painful and will end up with a lot of duplicated code since
there's also an order_by that follows the annotate that needs to be moved
over as well
Isn't there a way (even if it's hackish) to simply clear the annotations
(and order by)? I know querysets are smart enough to not include the order
by clause if there's a count.
You could also suggest using two separate calls or a flag to pass down to
the internal code so it doesn't include the additional stuff, but that
wouldn't work since paginators accept only one query set for example and
internall uses it for both count and results.
El viernes, 24 de noviembre de 2017, 0:05:29 (UTC-3), Simon Charette
escribió:
>
> Hello Cristiano,
>
> I understand your frustration but please avoid using the developer mailing
> list
> as a second tier support channel. I suggest you try the IRC #django
> channel if
> you need to want to get faster support.
>
> What's happening here is that annotate() really means "select this field"
> while
> in your other case you use a lookup (summary__icontains) which are only
> going to
> be added to the WHERE clause of your query.
>
> I'm not sure why you are annotating your queryset without referring to it
> in
> a filter clause later on but the ORM cannot simply ignore it when you are
> performing your `count()` because some annotations could interfere with
> grouping
> somehow.
>
> There is an open ticket[0] to add support for an `alias()` method that
> would
> allow the ORM to clear/ignore the specified expressions if it's not
> referenced
> in the query.
>
> In the mean time I think the best approach would be to avoid annotating the
> queryset if your don't need to reference the score.
>
> Cheers,
> Simon
>
> [0] https://code.djangoproject.com/ticket/27719
>
> Le mardi 21 novembre 2017 08:46:21 UTC-5, Cristiano Coelho a écrit :
>>
>> 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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Re: Strange query when using annotate and count
Hello Cristiano,
I understand your frustration but please avoid using the developer mailing
list
as a second tier support channel. I suggest you try the IRC #django channel
if
you need to want to get faster support.
What's happening here is that annotate() really means "select this field"
while
in your other case you use a lookup (summary__icontains) which are only
going to
be added to the WHERE clause of your query.
I'm not sure why you are annotating your queryset without referring to it in
a filter clause later on but the ORM cannot simply ignore it when you are
performing your `count()` because some annotations could interfere with
grouping
somehow.
There is an open ticket[0] to add support for an `alias()` method that would
allow the ORM to clear/ignore the specified expressions if it's not
referenced
in the query.
In the mean time I think the best approach would be to avoid annotating the
queryset if your don't need to reference the score.
Cheers,
Simon
[0] https://code.djangoproject.com/ticket/27719
Le mardi 21 novembre 2017 08:46:21 UTC-5, Cristiano Coelho a écrit :
>
> 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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Re: Strange query when using annotate and count
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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Strange query when using annotate and count
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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