#26782: DB Index key the same as Unique constraint key in seperate migrations
-------------------------------+--------------------------------------
Reporter: mackeyja92 | Owner: nobody
Type: Bug | Status: new
Component: Uncategorized | Version: 1.8
Severity: Normal | Resolution:
Keywords: db, migration | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------+--------------------------------------
Changes (by mackeyja92):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> When running a migration that has a db_index and a unique constraint it
> seems the same key is being used for both causing an error when applying
> migrations.
>
> Migration 1
>
> {{{
> class Migration(migrations.Migration):
>
> dependencies = [
> ('app', '0028_xxxx'),
> ]
>
> operations = [
> migrations.AlterField(
> model_name='model',
> name='uuid',
> field=models.CharField(db_index=True, max_length=36,
> blank=True, null=True, unique=False),
> ),
> ]
>
> }}}
>
> This migration runs the following SQL:
>
> {{{
> ALTER TABLE "table" ALTER COLUMN "uuid" DROP NOT NULL; (params [])
> CREATE INDEX "table_uuid_42f8156744ac727f_uniq" ON "table" ("uuid");
> (params [])
> CREATE INDEX "table_uuid_42f8156744ac727f_like" ON "table" ("uuid"
> varchar_pattern_ops); (params [])
> }}}
>
> Migration 2
>
> {{{
> def fill_uuids(apps, schema_editor):
> models = apps.get_model('app', 'model')
> models.objects.all().update(uuid=UUID1Now()) # Using postgres to
> generate uuid 1's
>
> def reverse_uuids(apps, schema_editor):
> models = apps.get_model('app', 'model')
> models.objects.all().update(uuid='')
>
> class Migration(migrations.Migration):
> dependencies = [
> ('app', '0029_xxxxx'),
> ]
>
> operations = [
> migrations.RunPython(fill_uuids, reverse_code=reverse_uuids),
> migrations.AlterField(
> model_name='model',
> name='uuid',
> field=models.CharField(db_index=True, max_length=36,
> blank=True, null=False, unique=True),
> ),
> ]
> }}}
>
> Migration 2 generates this SQL:
>
> {{{
> (0.146) UPDATE "table" SET "uuid" = uuid_generate_v1(); args=()
> ALTER TABLE "table" ALTER COLUMN "uuid" SET DEFAULT %s, ALTER COLUMN
> "uuid" SET NOT NULL; (params [u''])
> (0.002) ALTER TABLE "table" ALTER COLUMN "uuid" SET DEFAULT '', ALTER
> COLUMN "uuid" SET NOT NULL; args=[u'']
> ALTER TABLE "table" ADD CONSTRAINT "table_uuid_42f8156744ac727f_uniq"
> UNIQUE ("uuid"); (params [])
> (0.010) ALTER TABLE "table" ADD CONSTRAINT
> "table_uuid_42f8156744ac727f_uniq" UNIQUE ("uuid"); args=[]
> }}}
>
> That causes this exception `django.db.utils.ProgrammingError: relation
> "table_uuid_42f8156744ac727f_uniq" already exists`
New description:
When running a migration that has a db_index and a unique constraint it
seems the same key is being used for both causing an error when applying
migrations.
Migration 1
{{{
class Migration(migrations.Migration):
dependencies = [
('app', '0028_xxxx'),
]
operations = [
migrations.AlterField(
model_name='model',
name='uuid',
field=models.CharField(db_index=True, max_length=36,
blank=True, null=True, unique=False),
),
]
}}}
This migration runs the following SQL:
{{{
ALTER TABLE "table" ALTER COLUMN "uuid" DROP NOT NULL; (params [])
CREATE INDEX "table_uuid_42f8156744ac727f_uniq" ON "table" ("uuid");
(params [])
CREATE INDEX "table_uuid_42f8156744ac727f_like" ON "table" ("uuid"
varchar_pattern_ops); (params [])
}}}
Migration 2
{{{
def fill_uuids(apps, schema_editor):
models = apps.get_model('app', 'model')
models.objects.all().update(uuid=UUID1Now()) # Using postgres to
generate uuid 1's
def reverse_uuids(apps, schema_editor):
models = apps.get_model('app', 'model')
models.objects.all().update(uuid='')
class Migration(migrations.Migration):
dependencies = [
('app', '0029_xxxxx'),
]
operations = [
migrations.RunPython(fill_uuids, reverse_code=reverse_uuids),
migrations.AlterField(
model_name='model',
name='uuid',
field=models.CharField(db_index=True, max_length=36,
blank=True, null=False, unique=True),
),
]
}}}
Migration 2 generates this SQL:
{{{
(0.146) UPDATE "table" SET "uuid" = uuid_generate_v1(); args=()
ALTER TABLE "table" ALTER COLUMN "uuid" SET DEFAULT %s, ALTER COLUMN
"uuid" SET NOT NULL; (params [u''])
(0.002) ALTER TABLE "table" ALTER COLUMN "uuid" SET DEFAULT '', ALTER
COLUMN "uuid" SET NOT NULL; args=[u'']
ALTER TABLE "table" ADD CONSTRAINT "table_uuid_42f8156744ac727f_uniq"
UNIQUE ("uuid"); (params [])
(0.010) ALTER TABLE "table" ADD CONSTRAINT
"table_uuid_42f8156744ac727f_uniq" UNIQUE ("uuid"); args=[]
}}}
That causes this exception `django.db.utils.ProgrammingError: relation
"table_uuid_42f8156744ac727f_uniq" already exists`
A work around is to remove the `db_index` in migration 1.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/26782#comment:1>
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