I am getting my hands wet with Django and I created a few models with some relationships between them, I inspected the migration and it appears as though Django is overcomplicating the migration.
Here is a sample of my models
from django.db import models
class Product(models.Model):
id = models.CharField(max_length=15, primary_key=True)
name = models.CharField(max_length=100)
cost = models.DecimalField(max_digits=19, decimal_places=4)
class Store(models.Model):
name = models.CharField(max_length=25, primary_key=True)
order_commission = models.DecimalField(max_digits=4, decimal_places=2)
class Listing(models.Model):
product = models.ForeignKey(Product, on_delete=models.RESTRICT)
store = models.ForeignKey(Store, on_delete=models.RESTRICT)
price = models.DecimalField(max_digits=19, decimal_places=4)
class Sale(models.Model):
listing = models.ForeignKey(Listing, on_delete=models.RESTRICT)
quantity = models.IntegerField()
price = models.DecimalField(max_digits=19, decimal_places=4)
tax = models.DecimalField(max_digits=19, decimal_places=4)
This is the SQL Django generates for the migration (I get the SQL via $ ./manage.py sqlmigrate foo 0001)
BEGIN;
--
-- Create model Listing
--
CREATE TABLE "foo_listing" (
"id" integer NOT NULL PRIMARY KEY AUTOINCREMENT,
"price" decimal NOT NULL
);
--
-- Create model Product
--
CREATE TABLE "foo_product" (
"id" varchar(15) NOT NULL PRIMARY KEY,
"name" varchar(100) NOT NULL,
"cost" decimal NOT NULL
);
--
-- Create model Store
--
CREATE TABLE "foo_store" (
"name" varchar(25) NOT NULL PRIMARY KEY,
"order_commission" decimal NOT NULL
);
--
-- Create model Sale
--
CREATE TABLE "foo_sale" (
"id" integer NOT NULL PRIMARY KEY AUTOINCREMENT,
"quantity" integer NOT NULL,
"price" decimal NOT NULL,
"tax" decimal NOT NULL,
"listing_id" integer NOT NULL REFERENCES "foo_listing" ("id") DEFERRABLE INITIALLY DEFERRED
);
--
-- Add field product to listing
--
CREATE TABLE "new__foo_listing" (
"id" integer NOT NULL PRIMARY KEY AUTOINCREMENT,
"price" decimal NOT NULL,
"product_id" varchar(15) NOT NULL REFERENCES "foo_product" ("id") DEFERRABLE INITIALLY DEFERRED
);
INSERT INTO "new__foo_listing" ("id", "price", "product_id")
SELECT "id", "price", NULL FROM "foo_listing";
DROP TABLE "foo_listing";
ALTER TABLE "new__foo_listing" RENAME TO "foo_listing";
CREATE INDEX "foo_sale_listing_id_077299ff" ON "foo_sale" ("listing_id");
CREATE INDEX "foo_listing_product_id_2048e18c" ON "foo_listing" ("product_id");
--
-- Add field store to listing
--
CREATE TABLE "new__foo_listing" (
"id" integer NOT NULL PRIMARY KEY AUTOINCREMENT,
"price" decimal NOT NULL,
"product_id" varchar(15) NOT NULL REFERENCES "foo_product" ("id") DEFERRABLE INITIALLY DEFERRED, "store_id" varchar(25) NOT NULL REFERENCES "foo_store" ("name") DEFERRABLE INITIALLY DEFERRED
);
INSERT INTO "new__foo_listing" ("id", "price", "product_id", "store_id")
SELECT "id", "price", "product_id", NULL FROM "foo_listing";
DROP TABLE "foo_listing";
ALTER TABLE "new__foo_listing" RENAME TO "foo_listing";
CREATE INDEX "foo_listing_product_id_2048e18c" ON "foo_listing" ("product_id");
CREATE INDEX "foo_listing_store_id_42056821" ON "foo_listing" ("store_id");
COMMIT;
As you can see the migration first creates "foo_listing" without the ForeignKey to Product, then it creates a table "new__foo_listing" this time with the ForeignKey and then it drop the initial table (DROP TABLE "foo_listing";) and it renames the new one (ALTER TABLE "new__foo_listing" RENAME TO "foo_listing";)
Are my models complex that it requires such complex steps in the migration?