add migration

Author: arthanson

netbox_custom_objects/migrations/0015_widen_integer_columns.py

@@ -0,0 +1,64 @@
+"""
+Widen existing integer custom-object columns from 32-bit to 64-bit (bigint).
+
+Integer fields previously mapped to Django's IntegerField, i.e. a 32-bit signed
+PostgreSQL ``integer`` column (max 2_147_483_647). They now map to BigIntegerField
+(``bigint``). New columns are created as bigint automatically by the schema editor,
+but columns on already-created custom_objects_* tables must be widened in place.
+
+``integer -> bigint`` is a lossless widening (every int32 value fits in int64), so
+no USING clause or data transformation is needed. The conversion rewrites the table
+under an ACCESS EXCLUSIVE lock; this is fine for typical custom-object table sizes.
+
+The reverse is intentionally a no-op: narrowing bigint back to integer could fail or
+lose data for any value outside the 32-bit range.
+
+See issue #532.
+"""
+
+from django.db import migrations
+
+
+def widen_integer_columns(apps, schema_editor):
+    """ALTER every integer-typed custom-object column to bigint, in place."""
+    CustomObjectTypeField = apps.get_model("netbox_custom_objects", "CustomObjectTypeField")
+
+    # Drive off field metadata (not blind introspection of every custom_objects_*
+    # column) so we only touch user integer fields, never base-model columns
+    # inherited from NetBox mixins. After migration 0014 all field names are
+    # lowercase and the scalar column name equals the field name exactly.
+    integer_fields = CustomObjectTypeField.objects.filter(type="integer")
+
+    with schema_editor.connection.cursor() as cursor:
+        for field in integer_fields:
+            table_name = f"custom_objects_{field.custom_object_type_id}"
+            column_name = field.name
+
+            # Idempotent + safe: only act on a column that exists and is still a
+            # 32-bit integer. A no-op on fresh installs (already bigint) and on
+            # partial re-runs.
+            cursor.execute(
+                """
+                SELECT 1 FROM information_schema.columns
+                WHERE table_schema = current_schema()
+                  AND table_name = %s
+                  AND column_name = %s
+                  AND data_type = 'integer'
+                """,
+                [table_name, column_name],
+            )
+            if cursor.fetchone():
+                cursor.execute(
+                    f'ALTER TABLE "{table_name}" ALTER COLUMN "{column_name}" TYPE bigint'
+                )
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("netbox_custom_objects", "0014_fix_mixed_case_field_names"),
+    ]
+
+    operations = [
+        migrations.RunPython(widen_integer_columns, migrations.RunPython.noop),
+    ]