Sort order when loading related objects using selectinload in SQLAlchemy

Question

Is there a way to specify the sort order when loading related objects using the selectinload option in SQLAlchemy?

My SQLAlchemy version: 1.2.10 My python version: 3.6.6

Answer 1

One way is just to specify the default ordering of the relationship in your mapped class. In the example below, a query like query(Example).options(selectinload(Example.related_items)) would order the eager loaded related items by the id column.

from sqlalchemy import Column, Integer, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship

Base = declarative_base()

class Example(Base):
    __tablename__ = 'examples'
    id = Column(Integer, primary_key=True)
    related_items = relationship('RelatedItem', back_populates='example', order_by='RelatedItem.id')

class RelatedItem(Base):
    __tablename__ = 'related_items'
    id = Column(Integer, primary_key=True)
    example_id = Column(Integer, ForeignKey('examples.id'), nullable=False)
    example = relationship('Example', back_populates='related_items')