migrations(crons): Better index for latest query in api (#62774)

Adds `dangerous` migration to specifically index on `status=IN_PROGRESS`
for the api query, which uses the `monitor`.

migrations_lockfile.txt

@@ -9,5 +9,5 @@ feedback: 0003_feedback_add_env
 hybridcloud: 0009_make_user_id_optional_for_slug_reservation_replica
 nodestore: 0002_nodestore_no_dictfield
 replays: 0003_add_size_to_recording_segment
-sentry: 0629_eventattachment_index
+sentry: 0630_better_monitor_latest_index
 social_auth: 0002_default_auto_field

src/sentry/migrations/0630_better_monitor_latest_index.py

@@ -0,0 +1,34 @@
+# Generated by Django 3.2.23 on 2024-01-08 19:52
+
+from django.db import migrations, models
+
+from sentry.new_migrations.migrations import CheckedMigration
+
+
+class Migration(CheckedMigration):
+    # This flag is used to mark that a migration shouldn't be automatically run in production. For
+    # the most part, this should only be used for operations where it's safe to run the migration
+    # after your code has deployed. So this should not be used for most operations that alter the
+    # schema of a table.
+    # Here are some things that make sense to mark as dangerous:
+    # - Large data migrations. Typically we want these to be run manually by ops so that they can
+    #   be monitored and not block the deploy for a long period of time while they run.
+    # - Adding indexes to large tables. Since this can take a long time, we'd generally prefer to
+    #   have ops run this and not block the deploy. Note that while adding an index is a schema
+    #   change, it's completely safe to run the operation after the code has deployed.
+    is_dangerous = True
+
+    dependencies = [
+        ("sentry", "0629_eventattachment_index"),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name="monitorcheckin",
+            index=models.Index(
+                condition=models.Q(("status", 3)),
+                fields=["monitor", "-date_added"],
+                name="api_latest",
+            ),
+        ),
+    ]

src/sentry/monitors/models.py

@@ -468,6 +468,12 @@ class MonitorCheckIn(Model):
             # used for endpoints for monitor stats + list check-ins
             models.Index(fields=["monitor", "date_added", "status"]),
             # used for latest on api endpoints
+            models.Index(
+                fields=["monitor", "-date_added"],
+                condition=Q(status=CheckInStatus.IN_PROGRESS),
+                name="api_latest",
+            ),
+            # TODO(rjo100): to be removed when above is confirmed working
             models.Index(fields=["monitor", "status", "date_added"]),
             # used for has_newer_result + thresholds
             models.Index(fields=["monitor_environment", "date_added", "status"]),