Moved across assets_id sorting to use proper numeric values. Also mofifies SQL command to find free asset IDs so that it works on postgres.

assets/migrations/0008_auto_20191205_1354.py

@@ -0,0 +1,42 @@
+# Generated by Django 2.0.13 on 2019-12-05 13:54
+# Edited by Matthew Smith on same date.
+import re
+from django.db import migrations, models
+
+def forwards(apps, schema_editor):
+    AssetModel = apps.get_model('assets', 'Asset')
+    
+    for row in AssetModel.objects.all():
+
+        row.asset_id = row.asset_id.upper()
+        asset_search = re.search("^([A-Z0-9]*?[A-Z]?)([0-9]+)$", row.asset_id)
+        if asset_search is None: # If the asset_id doesn't have a number at the end
+            row.asset_id += "1"
+        
+        asset_search = re.search("^([A-Z0-9]*?[A-Z]?)([0-9]+)$", row.asset_id)
+        row.asset_id_prefix = asset_search.group(1)
+        row.asset_id_number = int(asset_search.group(2))
+
+        row.save(update_fields=['asset_id', 'asset_id_prefix', 'asset_id_number'])
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('assets', '0007_auto_20190108_0202_squashed_0014_auto_20191017_2052'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='asset',
+            name='asset_id_number',
+            field=models.IntegerField(default=0),
+            preserve_default=False,
+        ),
+        migrations.AddField(
+            model_name='asset',
+            name='asset_id_prefix',
+            field=models.CharField(default=0, max_length=5),
+            preserve_default=False,
+        ),
+        migrations.RunPython(forwards, reverse_code=migrations.RunPython.noop),
+    ]