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/forms.py

@@ -7,6 +7,7 @@ class AssetForm(forms.ModelForm):
     class Meta:
         model = models.Asset
         fields = '__all__'
+        exclude = ['asset_id_prefix', 'asset_id_number']
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)

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),
+    ]

assets/models.py

@@ -54,7 +54,7 @@ class Connector(models.Model):
 
 class Asset(models.Model):
     class Meta:
-        ordering = ['asset_id']
+        ordering = ['asset_id_prefix', 'asset_id_number']
         permissions = (
             ('asset_finance', 'Can see financial data for assets'),
             ('view_asset', 'Can view an asset')
@@ -83,13 +83,19 @@ class Asset(models.Model):
     circuits = models.IntegerField(blank=True, null=True)
     cores = models.IntegerField(blank=True, null=True)
 
-    def get_available_asset_id():
+    # Hidden asset_id components
+    # For example, if asset_id was "C1001" then asset_id_prefix would be "C" and number "1001"
+    asset_id_prefix = models.CharField(max_length=5)
+    asset_id_number = models.IntegerField()
+
+    def get_available_asset_id(wanted_prefix=""):
         sql = """
-        SELECT MIN(CAST(a.asset_id AS int))+1
+        SELECT a.asset_id_number+1
         FROM assets_asset a
         LEFT OUTER JOIN assets_asset b ON
-            (CAST(a.asset_id AS int) + 1 = CAST(b.asset_id AS int))
+            (a.asset_id_number + 1 = b.asset_id_number AND
-        WHERE b.asset_id IS NULL AND CAST(a.asset_id AS int) >= %s;
+            a.asset_id_prefix = b.asset_id_prefix)
+        WHERE b.asset_id IS NULL AND a.asset_id_number >= %s AND a.asset_id_prefix = '';
         """
         with connection.cursor() as cursor:
             cursor.execute(sql, [9000])
@@ -114,8 +120,11 @@ class Asset(models.Model):
             errdict["date_sold"] = ["Cannot sell an item before it is acquired"]
 
         self.asset_id = self.asset_id.upper()
-        if re.search("^[a-zA-Z0-9]+$", self.asset_id) is None:
+        asset_search = re.search("^([A-Z0-9]*?[A-Z]?)([0-9]+)$", self.asset_id)
+        if asset_search is None:
                 errdict["asset_id"] = ["An Asset ID can only consist of letters and numbers"]
+        self.asset_id_prefix = asset_search.group(1)
+        self.asset_id_number = int(asset_search.group(2))
 
         if self.purchase_price and self.purchase_price < 0:
             errdict["purchase_price"] = ["A price cannot be negative"]