如何在SerializerMethodFields之間共享查詢集？

Question

我有我用約一個團隊如何在體育聯盟進行顯示細節串行..

class TeamLeagueSerializer(ModelSerializer): 
    class Meta: 
     model = Team 
     fields = [...] 
    games_played = fields.SerializerMethodField() 
    games_won = fields.SerializerMethodField() 
    games_lost = fields.SerializerMethodField() 
    points_for = fields.SerializerMethodField() 
    ...etc... 

    def fixtures(self, team): 
     # Retrieves all relevant fixtures for a given season and a given team 
     return Fixture.objects.filter(Q(home_team=team) | Q(away_team=team), season=self.season) 

    def get_games_won(self, obj): 
     home_results = Q(home_team=obj, result__home_team_score__gt=F('result__away_team_score')) 
     away_results = Q(away_team=obj, result__away_team_score__gt=F('result__home_team_score')) 
     results = self.fixtures(obj).filter(home_results | away_results) 
     return results.count() 

    def get_games_lost(self, obj): 
     home_results = Q(home_team=obj, result__home_team_score__lt=F('result__away_team_score')) 
     away_results = Q(away_team=obj, result__away_team_score__lt=F('result__home_team_score')) 
     results = self.fixtures(obj).filter(home_results | away_results) 
     return results.count() 

這一切工作正常，但對於8支球隊的聯賽，這可能需要大約5秒鐘以完成，因爲每個SerializerMethodField是一個單獨的查詢正在完成..

這個代碼的非api版本更簡單與單個查詢集註釋此序列化程序試圖創建的每個屬性，而不是單個查詢。

因此，對於給定的序列化程序，是否可以做同樣的事情，並從單個查詢而不是多個構建序列化程序數據？

Answer 1

您可以在視圖集級別指定自定義查詢通過設置queryset屬性或重寫get_queryset。

該查詢可能是你在非API版本使用同一個。

該方法的結果將直接饋送序列化程序，因此每個額外的註釋將在那裏可用。您可能需要使用read_only=True標誌在串行器中定義帶註釋的字段。

Answer 2

夫婦可能的解決方案：

1）它們組合在一起成爲一個場

class TeamLeagueSerializer(ModelSerializer): 
    class Meta: 
     model = Team 
     fields = [...] 
    details = fields.SerializerMethodField() 

    def get_details(self, team): 
     #your non-api version of the code 
     return {games_played: fixtures, games_won: won, games_lost: lost} 

2）或者，如果你真的想保持API相同，另一種可能性是設置每個屬性作爲模型屬性，並有例如額外的緩存性能self._team_info保存查詢以備將來使用的結果：然後

class Team(models.Model): 
    #your fields 

    @property 
    def team_info(self): 
     if not hasattr(self, "_team_info"): 
       #Your non-api version of the code 
       self._team_info = #result of your query containing fixture info, games won, games lost, etc, .e.g. in a dictionary 
     return self._team_info 

    @property 
    def fixtures(self): 
     return self.team_info['fixtures'] 

    @property 
    def games_won(self): 
     return self.team_info['games_won'] 

    @property 
    def games_lost(self): 
     return self.team_info['games_won'] 

在seriali壽你不需要設置任何SerializerMethodFields，你可以參考games_won，games_lost和固定裝置在你的領域屬性：

class TeamLeagueSerializer(ModelSerializer): 
    class Meta: 
     model = Team 
     fields = [..., 'fixtures', 'games_won', 'games_lost']