From 96c789014f682eb9bd8eef98d1fe59ca03516e1b Mon Sep 17 00:00:00 2001
From: mirabilos <thorsten.glaser@teckids.org>
Date: Tue, 3 Sep 2019 23:32:26 +0200
Subject: [PATCH] =?UTF-8?q?Use=20an=20SQL=20=E2=80=9CWHERE=20NOT=20EXISTS?=
=?UTF-8?q?=E2=80=9D=20subclause.?=
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This is correct performance-wise (avoids the need for the database to
build the entire result set before filtering; Django users reported a
speed-up of factor 5‥2000 over naïve solutions) and (accepted by Nik)
even more legible.
---
biscuit/apps/alsijil/views.py | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/biscuit/apps/alsijil/views.py b/biscuit/apps/alsijil/views.py
index 69e10cdcd..57d1ab82b 100644
--- a/biscuit/apps/alsijil/views.py
+++ b/biscuit/apps/alsijil/views.py
@@ -2,7 +2,7 @@ from collections import OrderedDict
from typing import Optional
from django.contrib.auth.decorators import login_required
-from django.db.models import Q
+from django.db.models import Exists, OuterRef, Q
from django.http import HttpRequest, HttpResponse
from django.shortcuts import render
from django.views.decorators.cache import cache_page
@@ -41,13 +41,17 @@ def lesson(request: HttpRequest, week: Optional[int] = None, period_id: Optional
request.POST or None, instance=lesson_documentation, prefix='leson_documentation')
# Create all missing personal notes about members of all groups in lesson
- missing_persons = Person.objects.filter(
+ missing_persons = Person.objects.annotate(
+ no_personal_notes=~Exists(PersonalNote.objects.filter(
+ week=wanted_week,
+ lesson_period=lesson_period,
+ person__pk=OuterRef('pk')
+ ))
+ ).filter(
member_of__in=Group.objects.filter(pk__in=lesson_period.lesson.groups.all()),
- is_active=True
- ).exclude(
- personal_notes__week=wanted_week,
- personal_notes__lesson_period=lesson_period
- ).all()
+ is_active=True,
+ no_personal_notes=True
+ )
PersonalNote.objects.bulk_create([
PersonalNote(person=person, lesson_period=lesson_period,
week=wanted_wek) for person in missing_persons
--
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