#25253: MySQL migrations drop & recreate constraints unnecessarily when changing
attributes that don't affect the schema
--------------------------------------+------------------------------------
Reporter: trecouvr | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Migrations | Version: 1.8
Severity: Normal | Resolution:
Keywords: migrations m2m mysql | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by piquadrat):
For what it's worth, I'm also seeing this on PostgreSQL 9.1, Django 1.9.5
and psycopg2 2.6.1. Specifically, adding an `on_delete` argument to a
`ForeignKey` (but I was also able to reproduce it with just adding
`blank=True`) and then running `sqlmigrate` on the generated migration
results in this output:
{{{
BEGIN;
--
-- Alter field last_occurrence on event
--
ALTER TABLE "event_event" DROP CONSTRAINT
"last_occurrence_id_refs_id_9b97c921";
ALTER TABLE "event_event" ADD CONSTRAINT
"event_event_last_occurrence_id_a6d9e0d9_fk_event_instance_id" FOREIGN KEY
("last_occurrence_id") REFERENCES "event_instance" ("id") DEFERRABLE
INITIALLY DEFERRED;
COMMIT;
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/25253#comment:9>
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