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I have a class:
class Chart(Base):
__tablename__ = 'chart'
id = C('chart_id', Integer, primary_key=True)
element_id = C(Integer, ForeignKey('element.element_id'))
element = relationship(Element)
name = C(String)
def __init__(self, name):
self.name = name
Usage is pretty common,
chart = Chart('Some name')
chart.element_id = element_id
But chart.element is None after setting element_id. Is there any way to auto-load this relation for new object before flush/commit?
218
Update table elements in SQLAlchemy. Get the books to table from the Metadata object initialized while connecting to the database. Pass the update query to the execute() function and get all the results using fetchall() function. Use a for loop to iterate through the results.
backref keyword argument on the relationship() construct allows the automatic generation of a new relationship() that will be automatically be added to the ORM mapping for the related class. It will then be placed into a relationship.
lazy = 'dynamic': When querying with lazy = 'dynamic', however, a separate query gets generated for the related object. If you use the same query as 'select', it will return: You can see that it returns a sqlalchemy object instead of the city objects.
The loading of relationships falls into three categories; lazy loading, eager loading, and no loading. Lazy loading refers to objects are returned from a query without the related objects loaded at first.
The best option is
chart = Chart('Some name')
chart.element = element
Assign direct object to the relation ship. If you are assign element_id then until it flush it will be in memory. Internally it will fire a query SELECT * FROM ELEMENT WHERE ELEMENT.id = element_id but that element_id data is not store or it will be in memory.
So i suggest direct assign object if you don't want to flush.
Hope this will help you.
101
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