add idempotent mode

CHANGES.md

@@ -1,6 +1,7 @@
 # django-pg-zero-downtime-migrations changelog
 
 ## 0.15
+  - added idempotent mode and `ZERO_DOWNTIME_MIGRATIONS_IDEMPOTENT_SQL` setting
   - fixed django 3.2 degradation with missing `skip_default_on_alter` method
 
 ## 0.14

README.md

@@ -106,8 +106,23 @@ Define way to apply deferred sql, default `True`:
     ZERO_DOWNTIME_DEFERRED_SQL = True
 
 Allowed values:
-- `True` - run deferred sql similar to default django way.
-- `False` - run deferred sql as soon as possible.
+- `True` - run deferred sql similar to default django way
+- `False` - run deferred sql as soon as possible
+
+#### ZERO_DOWNTIME_MIGRATIONS_IDEMPOTENT_SQL
+
+Define idempotent mode, default `False`:
+
+    ZERO_DOWNTIME_MIGRATIONS_IDEMPOTENT_SQL = False
+
+Allowed values:
+- `True` - skip already applied sql migrations
+- `False` - standard non atomic django behaviour
+
+As this backend doesn't use transactions for migrations any failed migration can be cause of stopped process in intermediate state.
+To avoid manual schema manipulation idempotent mode allows to rerun failed migration after fixed issue (eg. data issue or long running CRUD queries).
+
+> _NOTE:_ idempotent mode checks rely only on name and index and constraint valid state, so it can ignore name collisions and recommended do not use it for CI checks.
 
 #### PgBouncer and timeouts
 

tests/apps/idempotency_add_auto_field_app/migrations/0001_initial.py

@@ -0,0 +1,25 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="RelatedTestTable",
+            fields=[
+                ("test_field_int", models.IntegerField(primary_key=True, serialize=False)),
+            ],
+        ),
+        migrations.CreateModel(
+            name="TestTable",
+            fields=[
+                ("id", models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name="ID")),
+                ("test_field_int", models.IntegerField()),
+                ("test_field_str", models.CharField(max_length=10)),
+            ],
+        ),
+    ]

tests/apps/idempotency_add_auto_field_app/migrations/0002_alter_relatedtesttable_test_field_int.py

@@ -0,0 +1,18 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    atomic = False
+
+    dependencies = [
+        ("idempotency_add_auto_field_app", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="relatedtesttable",
+            name="test_field_int",
+            field=models.AutoField(primary_key=True, serialize=False),
+        ),
+    ]

tests/apps/idempotency_add_auto_field_app/models.py

@@ -0,0 +1,10 @@
+from django.db import models
+
+
+class TestTable(models.Model):
+    test_field_int = models.IntegerField()
+    test_field_str = models.CharField(max_length=10)
+
+
+class RelatedTestTable(models.Model):
+    test_field_int = models.AutoField(primary_key=True)

tests/apps/idempotency_add_check_app/migrations/0001_initial.py

@@ -0,0 +1,42 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="RelatedTestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField(null=True)),
+            ],
+        ),
+        migrations.CreateModel(
+            name="TestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField()),
+                ("test_field_str", models.CharField(max_length=10)),
+            ],
+        ),
+    ]

tests/apps/idempotency_add_check_app/migrations/0002_relatedtesttable_idempotency_add_check_app_relatedtesttable_check.py

@@ -0,0 +1,20 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    atomic = False
+
+    dependencies = [
+        ("idempotency_add_check_app", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AddConstraint(
+            model_name="relatedtesttable",
+            constraint=models.CheckConstraint(
+                check=models.Q(("test_field_int__gt", 0)),
+                name="idempotency_add_check_app_relatedtesttable_check",
+            ),
+        ),
+    ]

tests/apps/idempotency_add_check_app/models.py

@@ -0,0 +1,18 @@
+from django.db import models
+
+
+class TestTable(models.Model):
+    test_field_int = models.IntegerField()
+    test_field_str = models.CharField(max_length=10)
+
+
+class RelatedTestTable(models.Model):
+    test_field_int = models.IntegerField(null=True)
+
+    class Meta:
+        constraints = [
+            models.CheckConstraint(
+                check=models.Q(test_field_int__gt=0),
+                name="idempotency_add_check_app_relatedtesttable_check",
+            )
+        ]

tests/apps/idempotency_add_column_app/migrations/0001_initial.py

@@ -0,0 +1,42 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="RelatedTestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField(null=True)),
+            ],
+        ),
+        migrations.CreateModel(
+            name="TestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField()),
+                ("test_field_str", models.CharField(max_length=10)),
+            ],
+        ),
+    ]

tests/apps/idempotency_add_column_app/migrations/0002_relatedtesttable_test_field_str.py

@@ -0,0 +1,18 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    atomic = False
+
+    dependencies = [
+        ("idempotency_add_column_app", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="relatedtesttable",
+            name="test_field_str",
+            field=models.CharField(max_length=10, null=True),
+        ),
+    ]

tests/apps/idempotency_add_column_app/models.py

@@ -0,0 +1,11 @@
+from django.db import models
+
+
+class TestTable(models.Model):
+    test_field_int = models.IntegerField()
+    test_field_str = models.CharField(max_length=10)
+
+
+class RelatedTestTable(models.Model):
+    test_field_int = models.IntegerField(null=True)
+    test_field_str = models.CharField(max_length=10, null=True)

tests/apps/idempotency_add_column_foreign_key_app/migrations/0001_initial.py

@@ -0,0 +1,42 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="RelatedTestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField(null=True)),
+            ],
+        ),
+        migrations.CreateModel(
+            name="TestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField()),
+                ("test_field_str", models.CharField(max_length=10)),
+            ],
+        ),
+    ]

tests/apps/idempotency_add_column_foreign_key_app/migrations/0002_relatedtesttable_test_model.py

@@ -0,0 +1,23 @@
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    atomic = False
+
+    dependencies = [
+        ("idempotency_add_column_foreign_key_app", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="relatedtesttable",
+            name="test_model",
+            field=models.ForeignKey(
+                null=True,
+                on_delete=django.db.models.deletion.CASCADE,
+                to="idempotency_add_column_foreign_key_app.testtable",
+            ),
+        ),
+    ]

tests/apps/idempotency_add_column_foreign_key_app/models.py

@@ -0,0 +1,11 @@
+from django.db import models
+
+
+class TestTable(models.Model):
+    test_field_int = models.IntegerField()
+    test_field_str = models.CharField(max_length=10)
+
+
+class RelatedTestTable(models.Model):
+    test_field_int = models.IntegerField(null=True)
+    test_model = models.ForeignKey(TestTable, null=True, on_delete=models.CASCADE)

tests/apps/idempotency_add_column_one_to_one_app/migrations/0001_initial.py

@@ -0,0 +1,42 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = []
+
+    operations = [
+        migrations.CreateModel(
+            name="RelatedTestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField(null=True)),
+            ],
+        ),
+        migrations.CreateModel(
+            name="TestTable",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("test_field_int", models.IntegerField()),
+                ("test_field_str", models.CharField(max_length=10)),
+            ],
+        ),
+    ]

tests/apps/idempotency_add_column_one_to_one_app/migrations/0002_relatedtesttable_test_model.py

@@ -0,0 +1,22 @@
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    atomic = False
+
+    dependencies = [
+        ("idempotency_add_column_one_to_one_app", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="relatedtesttable",
+            name="test_model",
+            field=models.OneToOneField(
+                null=True,
+                on_delete=django.db.models.deletion.CASCADE,
+                to="idempotency_add_column_one_to_one_app.testtable",
+            ),
+        ),
+    ]