[Django]-Django + PostgreSQL trigger causes "violates foreign key constraint"

This problem is by a “mutating table”, when DJANGO emulate the ON_CASCADE, first delete the row on table “ProductPricing” and the insert on “OldProductPricing” is over a row in “Product” which will disappear. You have other options:

1. Delete the trigger and manage the logic in the Product.save() and ProductPricing.save(), and change on_delete=CASCADE by on_delete=DO_NOTHING.

or

2. A log table (“OldProductPricing”) should keep the data for ever, and show all the changes in the history from “Product”, thus you should delete the foreign key from “OldProductPricing” to “Product.