SQLAlchemy: cascade delete

by

The problem is that sqlalchemy considers Child as the parent, because that is where you defined your relationship (it doesn’t care that you called it “Child” of course).

If you define the relationship on the Parent class instead, it will work:

children = relationship("Child", cascade="all,delete", backref="parent")

(note "Child" as a string: this is allowed when using the declarative style, so that you are able to refer to a class that is not yet defined)

You might want to add delete-orphan as well (delete causes children to be deleted when the parent gets deleted, delete-orphan also deletes any children that were “removed” from the parent, even if the parent is not deleted)

EDIT: just found out: if you really want to define the relationship on the Child class, you can do so, but you will have to define the cascade on the backref (by creating the backref explicitly), like this:

parent = relationship(Parent, backref=backref("children", cascade="all,delete"))

(implying from sqlalchemy.orm import backref)

More Related Contents:

  1. Bulk insert with SQLAlchemy ORM
  2. How can I verify Column data types in the SQLAlchemy ORM?
  3. SQLAlchemy: how to filter date field?
  4. Getting random row through SQLAlchemy
  5. Select NULL Values in SQLAlchemy
  6. using sqlalchemy to load csv file into a database
  7. Importing a CSV file into a sqlite3 database table using Python
  8. How do I get the “id” after INSERT into MySQL database with Python?
  9. SQLAlchemy create_all() does not create tables
  10. SQL Alchemy ORM returning a single column, how to avoid common post processing
  11. Python call sql-server stored procedure with table valued parameter
  12. Generate sql with subquery as a column in select statement using SQLAlchemy
  13. Django persistent database connection
  14. Complex foreign key constraint in SQLAlchemy
  15. Connection problems with SQLAlchemy and multiple processes
  16. How to upsert pandas DataFrame to Microsoft SQL Server table?
  17. SQLAlchemy: engine, connection and session difference
  18. SQLite Performance Benchmark — why is :memory: so slow…only 1.5X as fast as disk?
  19. Relations on composite keys using sqlalchemy
  20. SQLAlchemy default DateTime
  21. flake8 complains on boolean comparison “==” in filter clause
  22. SQLAlchemy – Mapping self-referential relationship as one to many (declarative form)
  23. Setting SQLAlchemy autoincrement start value
  24. flask-sqlalchemy or sqlalchemy
  25. How to set connection timeout in SQLAlchemy
  26. Reverse engineer SQLAlchemy declarative class definition from existing MySQL database?
  27. SQLAlchemy classes across files
  28. A good way to escape quotes in a database query string?
  29. How can I achieve a self-referencing many-to-many relationship on the SQLAlchemy ORM back referencing to the same attribute?
  30. flask sqlalchemy query with keyword as variable

Leave a Comment