I think this ticket http://code.djangoproject.com/ticket/12386
identifies a change in the m2m code which breaks backwards
compatibility.
Consider the following three apps and models:
AppA/models.py:
class ModelA(models.Model):
name = models.CharField(max_length=1024, default='', blank=True)
AppB/models.py:
class ModelB(models.Model):
name = models.CharField(max_length=1024, default='', blank=True)
ma = models.ManyToManyField('AppA.ModelA', blank=True, null=True,
related_name='mb')
mc = models.ManyToManyField('AppC.ModelC', blank=True, null=True,
related_name='mc')
AppC/models.py:
class ModelC(models.Model):
name = models.CharField(max_length=1024, default='', blank=True)
The SQL generated for the m2m fields in AppB is different for Django
1.1 and 1.2/trunk. This breaks backwards compatibility.
It seems that in some cases 1.2 names the m2m column 'app.model_id'
whereas 1.1 uses 'model_id' only - i.e. no 'app.'
This only seems to happen when there are more that one m2m fields in a
model. Tested with postgresql. The SQL output for the M2M table is
show below for the different Django versions.
Django 1.1
CREATE TABLE "AppB_modelb_mc" (
"id" serial NOT NULL PRIMARY KEY,
"modelb_id" integer NOT NULL REFERENCES "AppB_modelb" ("id")
DEFERRABLE INITIALLY DEFERRED,
"modelc_id" integer NOT NULL REFERENCES "AppC_modelc" ("id")
DEFERRABLE INITIALLY DEFERRED,
UNIQUE ("modelb_id", "modelc_id")
);
Django 1.2
CREATE TABLE "AppB_modelb_mc" (
"id" serial NOT NULL PRIMARY KEY,
"modelb_id" integer NOT NULL,
"appc.modelc_id" integer NOT NULL,
UNIQUE ("modelb_id", "appc.modelc_id")
);
1.1 = "modelc_id"
1.2 = "appc.modelc_id"
I've uploaded a little test project to the ticket which demonstrates.
Simon
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