SQLAlchemy:筛选多对多joindload

问题描述

我具有用于单词"和短语"之间多对多关联的当前表设置:

I have the current table setup for a many to many association between "words" and "phrases":

association_table_wp = Table('words_phras', Base.metadata,
                             autoload=True,
                             extend_existing=True)

class Phrase(Base):
    __tablename__ = 'phrases'
    __table_args__ = {'autoload': True}

    def __init__(self, phrase, explanation=None, active=False):
        self.phrase = phrase
        self.explanation = explanation
        self.active = active

class Word(Base):
    __tablename__ = 'words'
    __table_args__ = {'autoload': True}

    def __init__(self, word, word_id=None, active=False):
        self.word = word
        self.word_id = word_id
        self.active = active

Word.phrases = relationship(Phrase,
                            secondary=association_table_wp,
                            backref="words")

现在通常当我想查找一些单词及其词组时，我会使用:

Now normally when I want to look up some words and their phrases I use:

words = db_session.query(Word).filter(Word.id.in_(word_ids)).\
             options(joinedload(Word.phrases)).\
             all()

这使我可以访问words[i].phrases来访问与给定单词相关的短语.

This allows me to access words[i].phrases to access the phrases associated with a given word.

现在，这可以正常工作，但是请注意该活动"属性.我想过滤单词的短语，以便仅返回带有active == True的单词.如何才能做到这一点?我已经尝试了联接和eager_loading的几种组合，但没有一个能如我所愿.

Now, this works fine, but note that "active" property. I want to filter the words' phrases so that only ones with active == True are returned. How can this be done? I have tried several combinations of joins and eager_loading, but none of them have worked as I'd hope.

非常感谢您.

推荐答案

我认为 contains_eager() 是您要寻找的东西:

I think contains_eager() is what you're looking for:

words = db_session.query(Word).\
    join(Word.phrases).\
    options(contains_eager(Word.phrases)).\
    filter(Word.id.in_(word_ids)).\
    filter(Phrase.active == True)

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