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<p>我有一个教育网站,提供基于年级的课程。在</p>
<ol>
<li><p>GradeLevel表存储所有可能的等级。然后我有课程类别和课程表。</p></li>
<li><p>GradeLevel表与课程表和类别表建立了反向关系。</p></li>
<li><p>我在GradeLevel表中循环查看每个年级(8个年级),然后一路抓住各自的课程和类别。</p></li>
<li><p>完成后,我将收集到的所有课程和类别放入一个列表中,并将其传递给我的模板。</p></li>
</ol>
<p>现在,问题是Django至少对每个查询求值两次。第一次是第一次请求,第二次是我把它放进名单。(我正在使用itertools来链接结果。Itertools正在导致查询再次运行。)这有一个不利的影响,使我的服务器减速到爬行状态。在</p>
<p>我的问题是,是否有人可以看看我的模型和查询,并就如何更好地进行查询提出建议,以避免和/或减轻这一主要的性能瓶颈。在</p>
<p><strong>等级模型:</strong></p>
<pre><code>class GradeLevel(models.Model):
title = models.CharField('Grade',max_length=10, null=True, blank=True, db_index=True)
fullname = models.CharField('Description',max_length=100, null=True, blank=True, db_index=True)
</code></pre>
<p><strong>课程类别模型:</strong></p>
^{pr2}$
<p><strong>课程设置:</strong></p>
<pre><code>class LessonCurriculum(models.Model):
title = models.CharField(max_length=255, null=True, blank=True, db_index=True)
...
gradelevel = models.ManyToManyField(GradeLevel, related_name='grade_curriculum', null=True, blank=True)
</code></pre>
<p>我的观点:</p>
<pre><code>from itertools import chain
from operator import attrgetter
def my_view(request):
grade_pk = GradeLevel.objects.prefetch_related().get(title='pre-k')
grade_pk_categories = grade_pk.grade_cats.filter(active=True,featured=True)
grade_pk_galleries = grade_pk.grade_curriculum.filter(active=True,featured=True)
grade_k = GradeLevel.objects.prefetch_related().get(title='k')
grade_k_categories = grade_k.grade_cats.filter(active=True,featured=True)
grade_k_galleries = grade_k.grade_curriculum.filter(active=True,featured=True)
grade_1 = GradeLevel.objects.prefetch_related().get(title='1')
grade_1_categories = grade_1.grade_cats.filter(active=True,featured=True)
grade_1_galleries = grade_1.grade_curriculum.filter(active=True,featured=True)
grade_2 = GradeLevel.objects.prefetch_related().get(title='2')
grade_2_categories = grade_2.grade_cats.filter(active=True,featured=True)
grade_2_galleries = grade_2.grade_curriculum.filter(active=True,featured=True)
grade_3 = GradeLevel.objects.prefetch_related().get(title='3')
grade_3_categories = grade_3.grade_cats.filter(active=True,featured=True)
grade_3_galleries = grade_3.grade_curriculum.filter(active=True,featured=True)
grade_4 = GradeLevel.objects.prefetch_related().get(title='4')
grade_4_categories = grade_4.grade_cats.filter(active=True,featured=True)
grade_4_galleries = grade_4.grade_curriculum.filter(active=True,featured=True)
grade_5 = GradeLevel.objects.prefetch_related().get(title='5')
grade_5_categories = grade_5.grade_cats.filter(active=True,featured=True)
grade_5_galleries = grade_5.grade_curriculum.filter(active=True,featured=True)
grade_6 = GradeLevel.objects.prefetch_related().get(title='6')
grade_6_categories = grade_6.grade_cats.filter(active=True,featured=True)
grade_6_galleries = grade_6.grade_curriculum.filter(active=True,featured=True)
grade_7 = GradeLevel.objects.prefetch_related().get(title='7')
grade_7_categories = grade_7.grade_cats.filter(active=True,featured=True)
grade_7_galleries = grade_7.grade_curriculum.filter(active=True,featured=True)
grade_8 = GradeLevel.objects.prefetch_related().get(title='8')
grade_8_categories = grade_8.grade_curriculum.filter(active=True,featured=True)
grade_8_galleries = grade_8.grade_curriculum.filter(active=True,featured=True)
gallery_list = list(set(sorted(chain(grade_pk_categories,grade_pk_galleries,grade_k_categories,grade_k_galleries,grade_1_categories,grade_1_galleries,grade_2_categories,grade_2_galleries,grade_3_categories,grade_3_galleries,grade_4_categories,grade_4_galleries,grade_5_categories,grade_5_galleries,grade_6_categories,grade_6_galleries,grade_7_categories,grade_7_galleries,grade_8_categories,grade_8_galleries), key=attrgetter('display_order'))))
</code></pre>