#35635: Adding a field with a default in migrations following an index rename 
seems
to fail
-------------------------------------+-------------------------------------
     Reporter:  Raphael Gaschignard  |                     Type:  Bug
       Status:  new                  |                Component:
                                     |  Migrations
      Version:  5.0                  |                 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
-------------------------------------+-------------------------------------
 I have the following migration:

 {{{
     operations = [
         migrations.RenameIndex(
             model_name="taggeditem",
             new_name="taggit_tagg_content_8fc721_idx",
             old_fields=("content_type", "object_id"),
         ),
     ]

 }}}

 I have created another migration after this one:
 {{{
     dependencies = [
         (
             "taggit",
 "0006_rename_taggeditem_content_type_object_id_taggit_tagg_content_8fc721_idx",
         ),
     ]

     operations = [
         migrations.AddField(
             model_name="taggeditem",
             name="created_at",
             field=models.DateTimeField(
                 blank=True, default=django.utils.timezone.now, null=True
             ),
         ),
     ]
 }}}

 This gives the following for `sqlmigrate`:
 {{{
 BEGIN;
 --
 -- Add field created_at to taggeditem
 --
 CREATE TABLE "new__taggit_taggeditem" ("id" integer NOT NULL PRIMARY KEY
 AUTOINCREMENT, "created_at" datetime NULL, "object_id" integer NOT NULL,
 "content_type_id" integer NOT NULL REFERENCES "django_content_type" ("id")
 DEFERRABLE INITIALLY DEFERRED, "tag_id" integer NOT NULL REFERENCES
 "taggit_tag" ("id") DEFERRABLE INITIALLY DEFERRED, CONSTRAINT
 "taggit_taggeditem_content_type_id_object_id_tag_id_4bb97a8e_uniq" UNIQUE
 ("content_type_id", "object_id", "tag_id"));
 INSERT INTO "new__taggit_taggeditem" ("id", "object_id",
 "content_type_id", "tag_id", "created_at") SELECT "id", "object_id",
 "content_type_id", "tag_id", '2024-07-27 00:31:47.134946' FROM
 "taggit_taggeditem";
 DROP TABLE "taggit_taggeditem";
 ALTER TABLE "new__taggit_taggeditem" RENAME TO "taggit_taggeditem";
 CREATE INDEX "taggit_taggeditem_object_id_e2d7d1df" ON "taggit_taggeditem"
 ("object_id");
 CREATE INDEX "taggit_taggeditem_content_type_id_9957a03c" ON
 "taggit_taggeditem" ("content_type_id");
 CREATE INDEX "taggit_taggeditem_tag_id_f4f5b767" ON "taggit_taggeditem"
 ("tag_id");
 CREATE INDEX "taggit_tagg_content_8fc721_idx" ON "taggit_taggeditem"
 ("content_type_id", "object_id");
 CREATE INDEX "taggit_tagg_content_8fc721_idx" ON "taggit_taggeditem"
 ("content_type_id", "object_id");
 COMMIT;
 }}}

 Note in particular the creating of two indexes with the same name.


 Now, if I don't set a default in the `AddField` operation , the
 `sqlmigrate` result is simply as follows:

 {{{
 BEGIN;
 --
 -- Add field created_at to taggeditem
 --
 ALTER TABLE "taggit_taggeditem" ADD COLUMN "created_at" datetime NULL;
 COMMIT;
 }}}

 And if I comment out the `RenameIndex` operation, I only create the index
 once, not twice, avoiding the issue.

 Extra detail: I hit this because I have an index with a name, and then a
 `RenameIndex` operation that renames it.
 It seems like we would expect there to be a cleanup operation during a
 rename. Instead, it creates the migration twice.

 I have only tested this out with the SQLite driver, and I have a suspicion
 it's only happening there, because... well... this seems like something
 that would break elsewhere.

 Reproduced this with 5.1rc1 and 5.0.6

 Reproduction:

 - Checkout https://github.com/jazzband/django-taggit/tree/ticket-700
 - Install Django
 - Run `sample_taggit/manage.py migrate`
-- 
Ticket URL: <https://code.djangoproject.com/ticket/35635>
Django <https://code.djangoproject.com/>
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