From d889b003de00ad2da68df81bfd9c62925b0d34a6 Mon Sep 17 00:00:00 2001
From: Leonardo Lazzaro <llazzaro@dc.uba.ar>
Date: Tue, 17 Jan 2023 20:05:20 +0100
Subject: [PATCH] fix(periods): performance improvement to avoid nplus queries

---
 CHANGELOG                 |  4 ++++
 schedule/models/events.py |  9 +++++----
 tests/test_periods.py     | 40 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index 969e9afb..b45c0c45 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,7 @@
+0.10.1 - 2023-01-29
+
+- Periods performance improvement avoid nplus queries
+
 0.10.0 - 2022-08-21
 ===================
 
diff --git a/schedule/models/events.py b/schedule/models/events.py
index c450f952..bf6fa5f1 100644
--- a/schedule/models/events.py
+++ b/schedule/models/events.py
@@ -598,10 +598,11 @@ class Meta:
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
-        if not self.title and self.event_id:
-            self.title = self.event.title
-        if not self.description and self.event_id:
-            self.description = self.event.description
+        event = kwargs.get("event", None)
+        if not self.title and event:
+            self.title = event.title
+        if not self.description and event:
+            self.description = event.description
 
     def moved(self):
         return self.original_start != self.start or self.original_end != self.end
diff --git a/tests/test_periods.py b/tests/test_periods.py
index b55ef60f..eb8cd3a6 100644
--- a/tests/test_periods.py
+++ b/tests/test_periods.py
@@ -2,10 +2,12 @@
 
 import pytz
 from django.conf import settings
+from django.db import connection
 from django.test import TestCase
-from django.test.utils import override_settings
+from django.test.utils import CaptureQueriesContext, override_settings
 
 from schedule.models import Calendar, Event, Rule
+from schedule.models.events import Occurrence
 from schedule.periods import Day, Month, Period, Week, Year
 
 
@@ -38,6 +40,42 @@ def test_get_occurrences(self):
             ],
         )
 
+    def test_nplus_one_queries_event_period(self):
+        """Reproduces bug 420 occurences without title or desc will generate additional queries
+        to retrieve the event model
+        """
+        rule = Rule.objects.create(frequency="WEEKLY")
+        cal = Calendar.objects.get(name="MyCal")
+
+        event = Event.objects.create(
+            title="TEST",
+            start=datetime.datetime(2008, 1, 5, 8, 0, tzinfo=pytz.utc),
+            end=datetime.datetime(2023, 1, 5, 9, 0, tzinfo=pytz.utc),
+            end_recurring_period=datetime.datetime(2008, 5, 5, 0, 0, tzinfo=pytz.utc),
+            rule=rule,
+            calendar=cal,
+        )
+        for _ in range(0, 21):
+            # lets set occ without title and desc to use the event.title or event.desc
+            Occurrence.objects.create(
+                event=event,
+                start=datetime.datetime(2008, 1, 7, 8, 0, tzinfo=pytz.utc),
+                end=datetime.datetime(2008, 1, 7, 8, 0, tzinfo=pytz.utc),
+                original_start=datetime.datetime(2008, 1, 7, 8, 0, tzinfo=pytz.utc),
+                original_end=datetime.datetime(2008, 1, 7, 8, 0, tzinfo=pytz.utc),
+            )
+        period = Period(
+            events=[event],
+            start=datetime.datetime(2008, 1, 4, 7, 0, tzinfo=pytz.utc),
+            end=datetime.datetime(2023, 1, 21, 7, 0, tzinfo=pytz.utc),
+        )
+        with CaptureQueriesContext(connection) as ctx:
+            for occurrence in period.get_occurrences():
+                pass
+
+        executed_queries = len(ctx.captured_queries)
+        assert executed_queries == 1, len(ctx.captured_queries)
+
     def test_get_occurrences_with_sorting_options(self):
         period = Period(
             events=Event.objects.all(),