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POThe right way to auto filter SQLAlchemy queries?
 

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  1. POThe right way to auto filter SQLAlchemy queries?
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    <p>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:</p> <hr> <pre><code>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 &amp; criterion else: self._criterion = criterion </code></pre> <p>And it's used like this:</p> <pre><code>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('someone@some.com') </code></pre> <p>EmailInfo is the class that's mapped to the join table between emails and the other Modules that they're related to.</p> <p>Here's an example of a mapper:</p> <pre><code>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 </code></pre> <hr> <p>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...</p> <ol> <li>Is there a better way to do this, I'm not really happy with poking around with the internals of a compicated class like Query as I am.</li> <li>Has anyone solved this in a different way that they can share?</li> </ol>
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