id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
28846	SQLite schema editor clears deferred SQL on operation requiring table rebuilds	Yevhen Kozlov	nobody	"0. create a models.py, ''makemigrations'' for them

{{{
from django.db import models

class Test(models.Model):
	pass

class Test2(models.Model):
	title = models.CharField(max_length=50)
}}}

1. add manyToMany field only, ''makemigrations'':

{{{
from django.db import models

class Test(models.Model):
	pass

class Test2(models.Model):
	title = models.CharField(max_length=50)
	tests = models.ManyToManyField(Test)
}}}
 
Check with ''sqlmigrate'' there is table ..._test2_test with UNIQUE INDEX:

{{{
CREATE TABLE ""m2m_test2_tests"" (""id"" integer NOT NULL PRIMARY KEY AUTOINCREMENT, ""test2_id"" integer NOT NULL REFERENCES ""m2m_test2"" (""id""), ""test_id"" integer NOT NULL REFERENCES ""m2m_test"" (""id""));
CREATE UNIQUE INDEX ""m2m_test2_tests_test2_id_test_id_c4708311_uniq"" ON ""m2m_test2_tests"" (""test2_id"", ""test_id"");
CREATE INDEX ""m2m_test2_tests_test2_id_de2c1678"" ON ""m2m_test2_tests"" (""test2_id"");
CREATE INDEX ""m2m_test2_tests_test_id_9723a1f8"" ON ""m2m_test2_tests"" (""test_id"");
}}}

2. drop migration created at step 1 and change title field additionally(say, set max_length=100)

{{{
from django.db import models

class Test(models.Model):
	pass

class Test2(models.Model):
	title = models.CharField(max_length=100)
	tests = models.ManyToManyField(Test)
}}}

Then run ''makemigrations'' and check its output:

{{{
BEGIN;
--
-- Add field tests to test2
--
CREATE TABLE ""m2m_test2_tests"" (""id"" integer NOT NULL PRIMARY KEY AUTOINCREMENT, ""test2_id"" integer NOT NULL REFERENCES ""m2m_test2"" (""id""), ""test_id"" integer NOT NULL REFERENCES ""m2m_test"" (""id""));
--
-- Alter field title on test2
--
ALTER TABLE ""m2m_test2"" RENAME TO ""m2m_test2__old"";
CREATE TABLE ""m2m_test2"" (""id"" integer NOT NULL PRIMARY KEY AUTOINCREMENT, ""title"" varchar(50) NOT NULL);
INSERT INTO ""m2m_test2"" (""id"", ""title"") SELECT ""id"", ""title"" FROM ""m2m_test2__old"";
DROP TABLE ""m2m_test2__old"";
COMMIT;
}}}

So no UNIQUE constraint is generated for automatically created table if there is any other field changed in the same migration.
At least it happens as for SQLite"	Bug	closed	Migrations	1.11	Normal	fixed	SQLite, migration, manyToMany		Accepted	0	0	0	0	0	0