Fix: Postgres selection, DBENGINE and migrations (#12299)

src/documents/migrations/0006_document_content_length.py

@@ -0,0 +1,25 @@
+# Generated by Django 5.2.6 on 2026-01-24 07:33
+
+import django.db.models.functions.text
+from django.db import migrations
+from django.db import models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("documents", "0005_alter_document_checksum_unique"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="document",
+            name="content_length",
+            field=models.GeneratedField(
+                db_persist=True,
+                expression=django.db.models.functions.text.Length("content"),
+                null=False,
+                help_text="Length of the content field in characters. Automatically maintained by the database for faster statistics computation.",
+                output_field=models.PositiveIntegerField(default=0),
+            ),
+        ),
+    ]