[PATCH 1/2] REST: Resolve performance issues with '/events' web view

[Daniel Axtens]

Stephen Finucane <stephen at that.guru> writes:

> The dropdown select-based filters in the web view of the REST API have
> stung us a few times. In this case, populating these filters for the
> '/events' endpoint results in a huge query that hammers the database and
> results in seriously laggy responses.

This is good and solves the problem, thank you.

>
> The root cause of this performance issues was erroneously identified as
> an issue with the JSON renderer so that particular patch can now be
> reverted. This will be done separately.
>
> Signed-off-by: Stephen Finucane <stephen at that.guru>
> Cc: Daniel Axtens <dja at axtens.net>
> ---
> We might want to look at extending this to other endpoint, which are
> probably seeing similar issues (albeit, not as severe). I haven't done
> this yet though, out of fear of engaging in premature optimization
> [1].

It's definitely a problem with other endpoints: /api/patches takes ~10s.
I think it might end up being an issue with series and covers if we have
enough of them, but that doesn't show up on my test instance.

Tested-by: Daniel Axtens <dja at axtens.net>

Regards,
Daniel

>
> [1] https://xkcd.com/1691/
> ---
>  patchwork/api/filters.py | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/patchwork/api/filters.py b/patchwork/api/filters.py
> index f6fff792..7e818954 100644
> --- a/patchwork/api/filters.py
> +++ b/patchwork/api/filters.py
> @@ -24,6 +24,7 @@ from django_filters.rest_framework import FilterSet
>  from django_filters import IsoDateTimeFilter
>  from django_filters import ModelMultipleChoiceFilter
>  from django.forms import ModelMultipleChoiceField as BaseMultipleChoiceField
> +from django.forms.widgets import MultipleHiddenInput
>  
>  from patchwork.models import Bundle
>  from patchwork.models import Check
> @@ -200,10 +201,17 @@ class CheckFilterSet(TimestampMixin, FilterSet):
>  
>  class EventFilterSet(TimestampMixin, FilterSet):
>  
> -    project = ProjectFilter(queryset=Project.objects.all())
> -    series = BaseFilter(queryset=Series.objects.all())
> -    patch = BaseFilter(queryset=Patch.objects.all())
> -    cover = BaseFilter(queryset=CoverLetter.objects.all())
> +    # NOTE(stephenfin): We disable the select-based HTML widgets for these
> +    # filters as the resulting query is _huge_
> +    # TODO(stephenfin): We should really use an AJAX widget of some form here
> +    project = ProjectFilter(queryset=Project.objects.all(),
> +                            widget=MultipleHiddenInput)
> +    series = BaseFilter(queryset=Series.objects.all(),
> +                        widget=MultipleHiddenInput)
> +    patch = BaseFilter(queryset=Patch.objects.all(),
> +                       widget=MultipleHiddenInput)
> +    cover = BaseFilter(queryset=CoverLetter.objects.all(),
> +                       widget=MultipleHiddenInput)
>  
>      class Meta:
>          model = Event
> -- 
> 2.14.3