debug_toolbar報告的重複查詢

Question

我最近安裝了debug_toolbar到我的應用程序和它的報告中，查詢正在運行兩次。

debug_toolbar報告重複的數據庫查詢。

SET SQL_AUTO_IS_NULL = 0 
Duplicated 2 times. 

/Users/siquick/Django/soundshelter/soundshelterapp/views.py in release(128) 
    genre = [release['genre'] for release in context_dict['release']] 

的代碼片段從views.py是：

 release_list = Releases.objects.filter(id=release_id).values('all_artists','label_no_country','id','title','genre').annotate(cnt=Count('chartsextended'))[:1] 

     context_dict['release'] = release_list 

     genre = [release['genre'] for release in context_dict['release']] 
     label_no_country = [release['label_no_country'] for release in context_dict['release']] 
     all_artists = [release['all_artists'] for release in context_dict['release']] 
     title = [release['title'] for release in context_dict['release']] 

是什麼原因造成的重複？我知道這是由這條線genre = [release['genre'] for release in context_dict['release']]造成的，但不知道爲什麼會發生這種情況。

Answer 1

這是因爲我猜「流派」也是一種模式。

你應該使用select_related（'genre'）來獲取它們只有一次。 https://docs.djangoproject.com/en/1.9/ref/models/querysets/#select-related