add cached count fields to avoid expensive COUNT queries

errata/managers.py

@@ -19,4 +19,4 @@
 
 class ErratumManager(models.Manager):
     def get_queryset(self):
-        return super().get_queryset().select_related()
+        return super().get_queryset()

errata/templates/errata/erratum_detail.html

@@ -8,10 +8,11 @@
 
 {% block content %}
 
+{% with affected_count=erratum.affected_packages.count fixed_count=erratum.fixed_packages.count %}
 <ul class="nav nav-tabs">
   <li class="active"><a data-toggle="tab" href="#erratum_details">Details</a></li>
-  <li><a data-toggle="tab" href="#erratum_affected_packages">Packages Affected ({{ erratum.affected_packages.count }})</a></li>
-  <li><a data-toggle="tab" href="#erratum_fixed_packages">Packages Fixed ({{ erratum.fixed_packages.count }})</a></li>
+  <li><a data-toggle="tab" href="#erratum_affected_packages">Packages Affected ({{ affected_count }})</a></li>
+  <li><a data-toggle="tab" href="#erratum_fixed_packages">Packages Fixed ({{ fixed_count }})</a></li>
 </ul>
 
 <div class="tab-content">
@@ -22,8 +23,8 @@
         <tr><th class="col-sm-1">Type</th><td> {{ erratum.e_type }} </td></tr>
         <tr><th class="col-sm-1">Published Date</th><td>{{ erratum.issue_date|date|default_if_none:'' }}</td></tr>
         <tr><th class="col-sm-1">Synopsis</th><td> {{ erratum.synopsis }} </td></tr>
-        <tr><th class="col-sm-1">Packages Affected</th><td><a href="{% url 'packages:package_list' %}?erratum_id={{ erratum.id }}&type=affected"> {{ erratum.affected_packages.count }} </a></td></tr>
-        <tr><th class="col-sm-1">Packages Fixed</th><td><a href="{% url 'packages:package_list' %}?erratum_id={{ erratum.id }}&type=fixed"> {{ erratum.fixed_packages.count }} </a></td></tr>
+        <tr><th class="col-sm-1">Packages Affected</th><td><a href="{% url 'packages:package_list' %}?erratum_id={{ erratum.id }}&type=affected"> {{ affected_count }} </a></td></tr>
+        <tr><th class="col-sm-1">Packages Fixed</th><td><a href="{% url 'packages:package_list' %}?erratum_id={{ erratum.id }}&type=fixed"> {{ fixed_count }} </a></td></tr>
         <tr>
           <th class="col-sm-2">OS Releases Affected</th>
           <td>
@@ -78,5 +79,6 @@
     </div>
   </div>
 </div>
+{% endwith %}
 
 {% endblock %}

errata/views.py

@@ -29,7 +29,7 @@
 
 @login_required
 def erratum_list(request):
-    errata = Erratum.objects.select_related()
+    errata = Erratum.objects.all()
 
     if 'e_type' in request.GET:
         errata = errata.filter(e_type=request.GET['e_type']).distinct()

hosts/apps.py

@@ -19,3 +19,6 @@
 
 class HostsConfig(AppConfig):
     name = 'hosts'
+
+    def ready(self):
+        import hosts.signals  # noqa

hosts/managers.py

@@ -20,4 +20,4 @@
 
 class HostManager(models.Manager):
     def get_queryset(self):
-        return super().get_queryset().select_related()
+        return super().get_queryset().select_related('osvariant', 'arch', 'domain')

hosts/migrations/0011_host_bug_updates_count_host_errata_count_and_more.py

@@ -0,0 +1,33 @@
+# Generated by Django 4.2.28 on 2026-02-11 04:56
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('hosts', '0010_alter_hostrepo_options'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='host',
+            name='bug_updates_count',
+            field=models.PositiveIntegerField(db_index=True, default=0),
+        ),
+        migrations.AddField(
+            model_name='host',
+            name='errata_count',
+            field=models.PositiveIntegerField(db_index=True, default=0),
+        ),
+        migrations.AddField(
+            model_name='host',
+            name='packages_count',
+            field=models.PositiveIntegerField(db_index=True, default=0),
+        ),
+        migrations.AddField(
+            model_name='host',
+            name='sec_updates_count',
+            field=models.PositiveIntegerField(db_index=True, default=0),
+        ),
+    ]

hosts/migrations/0012_backfill_cached_counts.py

@@ -0,0 +1,33 @@
+# Generated by Django 4.2.28 on 2026-02-11
+
+from django.db import migrations
+
+
+def backfill_host_counts(apps, schema_editor):
+    """Backfill cached count fields for existing hosts."""
+    Host = apps.get_model('hosts', 'Host')
+    for host in Host.objects.all():
+        host.sec_updates_count = host.updates.filter(security=True).count()
+        host.bug_updates_count = host.updates.filter(security=False).count()
+        host.packages_count = host.packages.count()
+        host.errata_count = host.errata.count()
+        host.save(update_fields=[
+            'sec_updates_count', 'bug_updates_count',
+            'packages_count', 'errata_count'
+        ])
+
+
+def reverse_backfill(apps, schema_editor):
+    """No-op reverse - counts will be recalculated on next report."""
+    pass
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('hosts', '0011_host_bug_updates_count_host_errata_count_and_more'),
+    ]
+
+    operations = [
+        migrations.RunPython(backfill_host_counts, reverse_backfill),
+    ]

hosts/models.py

@@ -60,6 +60,11 @@ class Host(models.Model):
     tags = TaggableManager(blank=True)
     updated_at = models.DateTimeField(default=timezone.now)
     errata = models.ManyToManyField(Erratum, blank=True)
+    # Cached count fields for query optimization
+    sec_updates_count = models.PositiveIntegerField(default=0, db_index=True)
+    bug_updates_count = models.PositiveIntegerField(default=0, db_index=True)
+    packages_count = models.PositiveIntegerField(default=0, db_index=True)
+    errata_count = models.PositiveIntegerField(default=0, db_index=True)
 
     from hosts.managers import HostManager
     objects = HostManager()
@@ -97,20 +102,23 @@ def get_absolute_url(self):
         return reverse('hosts:host_detail', args=[self.hostname])
 
     def get_num_security_updates(self):
-        return self.updates.filter(security=True).count()
+        return self.sec_updates_count
 
     def get_num_bugfix_updates(self):
-        return self.updates.filter(security=False).count()
+        return self.bug_updates_count
 
     def get_num_updates(self):
-        return self.updates.count()
+        return self.sec_updates_count + self.bug_updates_count
 
     def get_num_packages(self):
-        return self.packages.count()
+        return self.packages_count
 
     def get_num_repos(self):
         return self.repos.count()
 
+    def get_num_errata(self):
+        return self.errata_count
+
     def check_rdns(self):
         if self.check_dns:
             update_rdns(self)
@@ -127,9 +135,9 @@ def clean_reports(self):
         """ Remove all but the last 3 reports for a host
         """
         from reports.models import Report
-        reports = Report.objects.filter(host=self).order_by('-created')[3:]
-        rlen = reports.count()
-        for report in Report.objects.filter(host=self).order_by('-created')[3:]:
+        reports = list(Report.objects.filter(host=self).order_by('-created')[3:])
+        rlen = len(reports)
+        for report in reports:
             report.delete()
         if rlen > 0:
             info_message(text=f'{self.hostname}: removed {rlen} old reports')
@@ -149,14 +157,14 @@ def get_host_repo_packages(self):
                 Q(mirror__repo__in=self.repos.all(),
                   mirror__enabled=True,
                   mirror__repo__enabled=True)
-        return Package.objects.select_related().filter(hostrepos_q).distinct()
+        return Package.objects.select_related('name', 'arch').filter(hostrepos_q).distinct()
 
     def process_update(self, package, highest_package):
         if self.host_repos_only:
             host_repos = Q(repo__host=self)
         else:
             host_repos = Q(repo__osrelease__osvariant__host=self, repo__arch=self.arch) | Q(repo__host=self)
-        mirrors = highest_package.mirror_set.filter(host_repos)
+        mirrors = highest_package.mirror_set.filter(host_repos).select_related('repo')
         security = False
         # if any of the containing repos are security, mark the update as a security update
         for mirror in mirrors:
@@ -215,7 +223,7 @@ def find_host_repo_updates(self, host_packages, repo_packages):
                         repo__mirror__refresh=True,
                         repo__mirror__repo__enabled=True,
                         host=self)
-        hostrepos = HostRepo.objects.select_related().filter(hostrepos_q)
+        hostrepos = HostRepo.objects.select_related('host', 'repo').filter(hostrepos_q)
 
         for package in host_packages:
             highest_package = package

hosts/serializers.py

@@ -33,10 +33,10 @@ class Meta:
                   'updated_at', 'bugfix_update_count', 'security_update_count')
 
     def get_bugfix_update_count(self, obj):
-        return obj.updates.filter(security=False).count()
+        return obj.bug_updates_count
 
     def get_security_update_count(self, obj):
-        return obj.updates.filter(security=True).count()
+        return obj.sec_updates_count
 
 
 class HostRepoSerializer(serializers.HyperlinkedModelSerializer):

hosts/signals.py

@@ -0,0 +1,45 @@
+# Copyright 2026 Marcus Furlong <furlongm@gmail.com>
+#
+# This file is part of Patchman.
+#
+# Patchman is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3 only.
+#
+# Patchman is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Patchman. If not, see <http://www.gnu.org/licenses/>
+
+from django.db.models.signals import m2m_changed
+from django.dispatch import receiver
+
+from hosts.models import Host
+
+
+@receiver(m2m_changed, sender=Host.packages.through)
+def update_host_packages_count(sender, instance, action, **kwargs):
+    """Update packages_count when Host.packages M2M changes."""
+    if action in ('post_add', 'post_remove', 'post_clear'):
+        instance.packages_count = instance.packages.count()
+        instance.save(update_fields=['packages_count'])
+
+
+@receiver(m2m_changed, sender=Host.updates.through)
+def update_host_updates_count(sender, instance, action, **kwargs):
+    """Update sec_updates_count and bug_updates_count when Host.updates M2M changes."""
+    if action in ('post_add', 'post_remove', 'post_clear'):
+        instance.sec_updates_count = instance.updates.filter(security=True).count()
+        instance.bug_updates_count = instance.updates.filter(security=False).count()
+        instance.save(update_fields=['sec_updates_count', 'bug_updates_count'])
+
+
+@receiver(m2m_changed, sender=Host.errata.through)
+def update_host_errata_count(sender, instance, action, **kwargs):
+    """Update errata_count when Host.errata M2M changes."""
+    if action in ('post_add', 'post_remove', 'post_clear'):
+        instance.errata_count = instance.errata.count()
+        instance.save(update_fields=['errata_count'])

hosts/tables.py

@@ -31,7 +31,7 @@
     '{% endwith %}'
 )
 AFFECTED_ERRATA_TEMPLATE = (
-    '{% with count=record.errata.count %}'
+    '{% with count=record.errata_count %}'
     '{% if count != 0 %}'
     '<a href="{% url \'errata:erratum_list\' %}?host={{ record.hostname }}">{{ count }}</a>'
     '{% else %}{% endif %}{% endwith %}'

hosts/tasks.py

@@ -15,7 +15,6 @@
 # along with Patchman. If not, see <http://www.gnu.org/licenses/>
 
 from celery import shared_task
-from django.db.models import Count
 
 from hosts.models import Host
 from util import get_datetime_now
@@ -34,47 +33,43 @@ def find_host_updates(host_id):
 def find_all_host_updates():
     """ Task to find updates for all hosts
     """
-    for host in Host.objects.all():
+    for host in Host.objects.all().iterator():
         find_host_updates.delay(host.id)
 
 
 @shared_task(priority=1)
 def find_all_host_updates_homogenous():
     """ Task to find updates for all hosts where hosts are expected to be homogenous
     """
-    updated_hosts = []
+    updated_host_ids = set()
     ts = get_datetime_now()
-    for host in Host.objects.all():
-        if host not in updated_hosts:
+    for host in Host.objects.all().iterator():
+        if host.id not in updated_host_ids:
             host.find_updates()
             host.updated_at = ts
             host.save()
 
             # only include hosts with the exact same number of packages
-            filtered_hosts = Host.objects.annotate(
-                packages_count=Count('packages')).filter(
-                    packages_count=host.packages.count()
-                )
+            filtered_hosts = Host.objects.filter(
+                packages_count=host.packages_count
+            )
             # and exclude hosts with the current timestamp
             filtered_hosts = filtered_hosts.exclude(updated_at=ts)
 
-            packages = set(host.packages.all())
-            repos = set(host.repos.all())
-            updates = host.updates.all()
+            package_ids = frozenset(host.packages.values_list('id', flat=True))
+            repo_ids = frozenset(host.repos.values_list('id', flat=True))
+            updates = list(host.updates.all())
 
-            phosts = []
-            for fhost in filtered_hosts:
-                frepos = set(fhost.repos.all())
-                if repos != frepos:
+            for fhost in filtered_hosts.iterator():
+                frepo_ids = frozenset(fhost.repos.values_list('id', flat=True))
+                if repo_ids != frepo_ids:
                     continue
-                fpackages = set(fhost.packages.all())
-                if packages != fpackages:
+                fpackage_ids = frozenset(fhost.packages.values_list('id', flat=True))
+                if package_ids != fpackage_ids:
                     continue
-                phosts.append(fhost)
 
-            for phost in phosts:
-                phost.updates.set(updates)
-                phost.updated_at = ts
-                phost.save()
-                updated_hosts.append(phost)
-                info_message(text=f'Added the same updates to {phost}')
+                fhost.updates.set(updates)
+                fhost.updated_at = ts
+                fhost.save()
+                updated_host_ids.add(fhost.id)
+                info_message(text=f'Added the same updates to {fhost}')