Mail: Remove redundant SQL queries

On my local test event, this saved 75 queries on sending an email due to
an N+1 query problem in the metadata querying.

src/pretix/base/modelimport_vouchers.py

@@ -132,7 +132,7 @@ class AllowIgnoreQuotaColumn(BooleanColumnMixin, ImportColumn):
 
 class PriceModeColumn(ImportColumn):
     identifier = 'price_mode'
-    verbose_name = gettext_lazy('Price effect')
+    verbose_name = gettext_lazy('Price mode')
     default_value = None
     initial = 'static:none'
 
@@ -147,7 +147,7 @@ class PriceModeColumn(ImportColumn):
         elif value in reverse:
             return reverse[value]
         else:
-            raise ValidationError(_("Could not parse {value} as a price effect, use one of {options}.").format(
+            raise ValidationError(_("Could not parse {value} as a price mode, use one of {options}.").format(
                 value=value, options=', '.join(d.keys())
             ))
 
@@ -162,7 +162,7 @@ class ValueColumn(DecimalColumnMixin, ImportColumn):
     def clean(self, value, previous_values):
         value = super().clean(value, previous_values)
         if value and previous_values.get("price_mode") == "none":
-            raise ValidationError(_("It is pointless to set a value without a price effect."))
+            raise ValidationError(_("It is pointless to set a value without a price mode."))
         return value
 
     def assign(self, value, obj: Voucher, **kwargs):

src/pretix/base/models/vouchers.py

@@ -239,7 +239,7 @@ class Voucher(LoggedModel):
         )
     )
     price_mode = models.CharField(
-        verbose_name=_("Price effect"),
+        verbose_name=_("Price mode"),
         max_length=100,
         choices=PRICE_MODES,
         default='none'

src/pretix/base/services/mail.py

@@ -409,6 +409,18 @@ def mail_send_task(self, **kwargs) -> bool:
         outgoing_mail.inflight_since = now()
         outgoing_mail.save(update_fields=["status", "inflight_since"])
 
+    # Performance optimization, saves database queries later on if we resolve the known relationships
+    if outgoing_mail.event_id:
+        assert outgoing_mail.event.organizer_id == outgoing_mail.organizer.pk
+        outgoing_mail.event.organizer = outgoing_mail.organizer
+    if outgoing_mail.order_id:
+        assert outgoing_mail.order.event_id == outgoing_mail.event_id
+        outgoing_mail.order.event = outgoing_mail.event
+        outgoing_mail.order.organizer = outgoing_mail.organizer
+    if outgoing_mail.orderposition_id:
+        assert outgoing_mail.orderposition.order_id == outgoing_mail.order_id
+        outgoing_mail.orderposition.order = outgoing_mail.order
+
     headers = dict(outgoing_mail.headers)
     headers.setdefault('X-PX-Correlation', str(outgoing_mail.guid))
     email = CustomEmail(

src/pretix/base/services/placeholders.py

@@ -24,6 +24,7 @@ import logging
 from datetime import timedelta
 from decimal import Decimal
 
+from django.db.models import Prefetch, prefetch_related_objects
 from django.dispatch import receiver
 from django.utils.formats import date_format
 from django.utils.html import escape, mark_safe
@@ -35,6 +36,7 @@ from pretix.base.forms.widgets import format_placeholders_help_text
 from pretix.base.i18n import (
     LazyCurrencyNumber, LazyDate, LazyExpiresDate, LazyNumber,
 )
+from pretix.base.models import EventMetaValue
 from pretix.base.reldate import RelativeDateWrapper
 from pretix.base.settings import PERSON_NAME_SCHEMES, get_name_parts_localized
 from pretix.base.signals import (
@@ -752,6 +754,11 @@ def base_placeholders(sender, **kwargs):
             name_scheme['sample'][f]
         ))
 
+    prefetch_related_objects(
+        [sender],
+        Prefetch('meta_values', queryset=EventMetaValue.objects.select_related("property"), to_attr="meta_values_cached")
+    )
+    prefetch_related_objects([sender.organizer], Prefetch('meta_properties'))
     for k, v in sender.meta_data.items():
         ph.append(MarkdownTextPlaceholder(
             'meta_%s' % k, ['event'], lambda event, k=k: event.meta_data[k],

src/pretix/presale/templates/pretixpresale/event/resend_link.html

@@ -1,14 +1,14 @@
 {% extends "pretixpresale/event/base.html" %}
 {% load i18n %}
 {% load bootstrap3 %}
-{% block title %}{% trans "Resend order link" %}{% endblock %}
+{% block title %}{% trans "Resend order links" %}{% endblock %}
 {% block custom_header %}
     {{ block.super }}
     <meta name="robots" content="noindex, nofollow">
 {% endblock %}
 {% block content %}
     <h2>
-        {% trans "Resend order link" %}
+        {% trans "Resend order links" %}
     </h2>
     <p>
         {% blocktrans trimmed %}

src/pretix/presale/views/order.py

@@ -1510,10 +1510,7 @@ class OrderChangeMixin:
                             'max_count': iao.max_count,
                             'iao': iao,
                             'items': [i for i in items if not i.require_voucher],
-                            'items_missing': {
-                                k: v for k, v in current_addon_products_missing.items()
-                                if v and k[0].category_id == iao.addon_category_id
-                            },
+                            'items_missing': {k: v for k, v in current_addon_products_missing.items() if v},
                         })
 
         return positions

src/tests/base/test_modelimport_vouchers.py

@@ -170,7 +170,7 @@ def test_price_mode_validation(event, item, user):
         import_vouchers.apply(
             args=(event.pk, inputfile_factory().id, settings, 'en', user.pk)
         ).get()
-    assert 'It is pointless to set a value without a price effect.' in str(excinfo.value)
+    assert 'It is pointless to set a value without a price mode.' in str(excinfo.value)
 
     settings['price_mode'] = 'static:percent'
     import_vouchers.apply(