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Is it possible in sqlalchemy to lazy load a column? I have large BLOB column that I'm usually using but in some cases I don't want to load this specific column (while I'd like to have ORM object). Is it possible without adding separate table?
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Lazy loading refers to objects are returned from a query without the related objects loaded at first. When the given collection or reference is first accessed on a particular object, an additional SELECT statement is emitted such that the requested collection is loaded.
To access the column names we can use the method keys() on the result. It returns a list of column names. Since, we queried only three columns, we can view the same columns on the output as well.
The sqlalchemy backref is one of the type keywords and it passed as the separate argument parameters which has to be used in the ORM mapping objects. It mainly includes the event listener on the configuration attributes with both directions of the user datas through explicitly handling the database relationships.
with_entities() can either add or remove (simply: replace) models or columns; you can even use it to modify the query, to replace selected entities with your own function like func.count() : query = User.query count_query = query.with_entities(func.count(User.
class Book(Base):
__tablename__ = 'books'
book_id = Column(Integer, primary_key=True)
title = Column(String(200), nullable=False)
summary = Column(String(2000))
excerpt = deferred(Column(Text))
photo = deferred(Column(Binary))
Deferred Column Loading
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