Re: [Django] #27151: FK index created two times if referenced table PK is varchar

[Django]

#27151: FK index created two times if referenced table PK is varchar
-+--
 Reporter:  kkujawinski  |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.8
 Severity:  Normal   |   Resolution:
 Keywords:   | Triage Stage:  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+--
Changes (by timgraham):

 * needs_better_patch:   => 0
 * needs_tests:   => 0
 * needs_docs:   => 0


Comment:

 Could you please check if the issue still exists on Django master?

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[Django] #27151: FK index created two times if referenced table PK is varchar

[Django]

#27151: FK index created two times if referenced table PK is varchar
-+
 Reporter:  kkujawinski  |  Owner:  nobody
 Type:  Bug  | Status:  new
Component:  Migrations   |Version:  1.8
 Severity:  Normal   |   Keywords:
 Triage Stage:  Unreviewed   |  Has patch:  0
Easy pickings:  0|  UI/UX:  0
-+
 Django version: 1.8.14


 '''Scenario 1. with creating index only'''

 1. Initial models:

 {{{
 class Foo(models.Model):
 guid = models.CharField(max_length=36, primary_key=True)


 class Bar(models.Model):
 key = models.ForeignKey(Foo, db_index=False)
 }}}



 2. Initial migration:



 {{{
 class Migration(migrations.Migration):

 dependencies = []

 operations = [
 migrations.CreateModel(
 name='Bar',
 fields=[
 ('id', models.AutoField(verbose_name='ID',
 serialize=False, auto_created=True, primary_key=True)),
 ],
 ),
 migrations.CreateModel(
 name='Foo',
 fields=[
 ('guid', models.CharField(max_length=36, serialize=False,
 primary_key=True)),
 ],
 ),
 migrations.AddField(
 model_name='bar',
 name='key',
 field=models.ForeignKey(to='myapp.Foo', db_index=False),
 ),
 ]

 }}}


 3. Changes in to model:


 {{{
 -key = models.ForeignKey(Foo, db_index=False)
 +key = models.ForeignKey(Foo, db_index=True)

 }}}


 4. Migration:



 {{{
 class Migration(migrations.Migration):

 dependencies = [
 ('myapp', '0001_initial'),
 ]

 operations = [
 migrations.AlterField(
 model_name='bar',
 name='key',
 field=models.ForeignKey(to='myapp.Foo'),
 ),
 ]

 }}}


 5. Applying migration logs:


 {{{
 Operations to perform:
   Apply all migrations: myapp
 Running migrations:
   Rendering model states... DONE
   Applying myapp.0002_auto_20160829_1936...[2016-08-29 19:37:55,385
 pid=11084] DEBUG| django.db.backends.schema | ALTER TABLE "myapp_bar"
 DROP CONSTRAINT "myapp_bar_key_id_1647a22de55ad985_fk_myapp_foo_id";
 (params [])
 [2016-08-30 11:26:19,228 pid=25347] DEBUG| django.db.backends.schema |
 ALTER TABLE "myapp_bar" DROP CONSTRAINT
 "myapp_bar_key_id_1647a22de55ad985_fk_myapp_foo_guid"; (params [])
 [2016-08-30 11:26:19,230 pid=25347] DEBUG| django.db.backends.schema |
 CREATE INDEX "myapp_bar_key_id_1647a22de55ad985_uniq" ON "myapp_bar"
 ("key_id"); (params [])
 [2016-08-30 11:26:19,230 pid=25347] DEBUG| django.db.backends.schema |
 CREATE INDEX "myapp_bar_key_id_1647a22de55ad985_uniq" ON "myapp_bar"
 ("key_id"); (params [])
 [2016-08-30 11:26:19,235 pid=25347] DEBUG| django.db.backends.schema |
 ALTER TABLE "myapp_bar" ADD CONSTRAINT
 "myapp_bar_key_id_1647a22de55ad985_fk_myapp_foo_guid" FOREIGN KEY
 ("key_id") REFERENCES "myapp_foo" ("guid") DEFERRABLE INITIALLY DEFERRED;
 (params [])
 [2016-08-30 11:26:19,235 pid=25347] DEBUG| django.db.backends.schema |
 ALTER TABLE "myapp_bar" ADD CONSTRAINT
 "myapp_bar_key_id_1647a22de55ad985_fk_myapp_foo_guid" FOREIGN KEY
 ("key_id") REFERENCES "myapp_foo" ("guid") DEFERRABLE INITIALLY DEFERRED;
 (params [])
 [2016-08-30 11:26:19,237 pid=25347] DEBUG| django.db.backends.schema |
 CREATE INDEX "myapp_bar_key_id_1647a22de55ad985_like" ON "myapp_bar"
 ("key_id" varchar_pattern_ops); (params [])
 [2016-08-30 11:26:19,237 pid=25347] DEBUG| django.db.backends.schema |
 CREATE INDEX "myapp_bar_key_id_1647a22de55ad985_like" ON "myapp_bar"
 ("key_id" varchar_pattern_ops); (params [])
  OK


 }}}

 6. Indexes created in postgres database


 {{{
 SELECT i.relname as indname, i.relowner as indowner,
 idx.indrelid::regclass, am.amname as indam, idx.indkey,
ARRAY(SELECT pg_get_indexdef(idx.indexrelid, k + 1, true) FROM
 generate_subscripts(idx.indkey, 1) as k
  ORDER BY k) as indkey_names, idx.indexprs IS NOT NULL as
 indexprs, idx.indpred IS NOT NULL as indpred,
idx.indisunique
 FROM   pg_index as idx JOIN pg_class as i ON i.oid = idx.indexrelid JOIN
 pg_am as am ON i.relam = am.oid
 WHERE  idx.indrelid::regclass='myapp_bar'::regclass;

 indname | indowner | indrelid  | indam |
 indkey | indkey_names | indexprs | indpred | indisunique
 
+--+---+---++--+--+-+-
  myapp_bar_key_id_1647a22de55ad985_like |16384 | myapp_bar | btree | 2
 | {key_id} | f| f   | f
  myapp_bar_key_id_1647a22de55ad985_uniq |16384 | myapp_bar | btree | 2
 | {key_id} | f| f   | f
  myapp_bar_pkey |16384 | myapp_bar | btree | 1
 | {id} | f| f   | t


 }}}

 '''Scenario 2. indexes created in first