自动过滤 SQLAlchemy 查询的正确方法? [英] The right way to auto filter SQLAlchemy queries?

问题描述

我刚刚使用 sqlalchemy 从 CRM 应用程序中反省了一个非常讨厌的架构.所有表上都有一个已删除的列，我想自动过滤所有标记为已删除的实体和关系.这是我想出的:

I've just introspected a pretty nasty schema from a CRM app with sqlalchemy. All of the tables have a deleted column on them and I wanted to auto filter all those entities and relations flagged as deleted. Here's what I came up with:

class CustomizableQuery(Query):
    """An overridden sqlalchemy.orm.query.Query to filter entities

    Filters itself by BinaryExpressions
    found in :attr:`CONDITIONS`
    """

    CONDITIONS = []

    def __init__(self, mapper, session=None):
        super(CustomizableQuery, self).__init__(mapper, session)
        for cond in self.CONDITIONS:
            self._add_criterion(cond)

    def _add_criterion(self, criterion):
        criterion = self._adapt_clause(criterion, False, True)
        if self._criterion is not None:
            self._criterion = self._criterion & criterion
        else:
            self._criterion = criterion

它是这样使用的:

class UndeletedContactQuery(CustomizableQuery):
    CONDITIONS = [contacts.c.deleted != True]

    def by_email(self, email_address):
        return EmailInfo.query.by_module_and_address('Contacts', email_address).contact

    def by_username(self, uname):
        return self.filter_by(twod_username_c=uname).one()

class Contact(object):
    query = session.query_property(UndeletedContactQuery)

Contact.query.by_email('[e-mail]')

EmailInfo 是映射到电子邮件与其相关的其他模块之间的连接表的类.

EmailInfo is the class that's mapped to the join table between emails and the other Modules that they're related to.

以下是映射器的示例:

contacts_map = mapper(Contact, join(contacts, contacts_cstm), {
    '_emails': dynamic_loader(EmailInfo,
                              foreign_keys=[email_join.c.bean_id],
                              primaryjoin=contacts.c.id==email_join.c.bean_id,
                              query_class=EmailInfoQuery),
    })

class EmailInfoQuery(CustomizableQuery):

    CONDITIONS = [email_join.c.deleted != True]
    # More methods here

<小时>

这给了我我想要的，因为我已经过滤掉了所有已删除的联系人.我也可以在我的映射器中将其用作 dynamic_loader 的 query_class 参数 - 但是...

---

This gives me what I want in that I've filtered out all deleted Contacts. I can also use this as the query_class argument to dynamic_loader in my mappers - However...

1. 有没有更好的方法可以做到这一点，我不太喜欢在像 Query 这样的复杂类的内部进行探索.
2. 有没有人用他们可以分享的不同方式解决了这个问题?

推荐答案

您可以映射到选择.像这样:

You can map to a select. Like this:

mapper(EmailInfo, select([email_join], email_join.c.deleted == False))

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