#33125: Changing model field to become PK creates redundant UNIQUE constraint
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Reporter: Fabio Sangiovanni | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: dev
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Hi,
when swapping the `primary_key=True` attribute between two model fields,
`migrations.AlterField` seems to generate a redundant UNIQUE constraint
involving the new PK field.
To reproduce:
Prerequisites:
PostgreSQL 11.12
Python 3.8
Django main@7d909b2282c91c5bc5204dd160412e90fa86d624
Before state:
{{{
class Pony(models.Model):
name = models.CharField(max_length=32, primary_key=True)
nickname = models.CharField(max_length=32)
}}}
sqlmigrate:
{{{
BEGIN;
--
-- Create model Pony
--
CREATE TABLE "app_pony" ("name" varchar(32) NOT NULL PRIMARY KEY,
"nickname" varchar(32) NOT NULL);
CREATE INDEX "app_pony_name_204da2d2_like" ON "app_pony" ("name"
varchar_pattern_ops);
COMMIT;
}}}
After state:
{{{
class Pony(models.Model):
name = models.CharField(max_length=32)
nickname = models.CharField(max_length=32, primary_key=True)
}}}
sqlmigrate:
{{{
BEGIN;
--
-- Alter field name on pony
--
DROP INDEX IF EXISTS "app_pony_name_204da2d2_like";
--
-- Alter field nickname on pony
--
ALTER TABLE "app_pony" ADD CONSTRAINT "app_pony_nickname_1b2a0f82_uniq"
UNIQUE ("nickname");
ALTER TABLE "app_pony" ADD CONSTRAINT "app_pony_nickname_1b2a0f82_pk"
PRIMARY KEY ("nickname");
CREATE INDEX "app_pony_nickname_1b2a0f82_like" ON "app_pony" ("nickname"
varchar_pattern_ops);
COMMIT;
}}}
The `app_pony_nickname_1b2a0f82_uniq` constraint looks reduntant to me,
since the `nickname` field is going to become PK anyways.
Please let me know if I'm missing something or if I can be of further
help.
Thanks,
Fabio
--
Ticket URL: <https://code.djangoproject.com/ticket/33125>
Django <https://code.djangoproject.com/>
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