Add db indexes to user table (#3067)

Add composite indexes based on existing queries/usage, ensuring partial
index prefixes are useful too.

- `is_active` filtering is set in the default `User` manager
- most of our user queries are per `organization`
- multiple cases filter by `username` or `email` (most notably schedule
related queries, given the low-level backend ical representation)

Also rework how users are fetched from DB when getting users from
schedules ical representation (which was particularly slow when regex
filtering by required permission).

Related to https://github.com/grafana/oncall-private/issues/2163

CHANGELOG.md

@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Fix regression in public actions endpoint handling user field by @mderynck ([#3053](https://github.com/grafana/oncall/pull/3053))
 
+### Changed
+
+- Rework how users are fetched from DB when getting users from schedules ical representation ([#3067](https://github.com/grafana/oncall/pull/3067))
+
 ## v1.3.38 (2023-09-19)
 
 ### Fixed

engine/apps/schedules/ical_utils.py

@@ -67,11 +67,10 @@ IcalEvents = typing.List[IcalEvent]
 def users_in_ical(
     usernames_from_ical: typing.List[str],
     organization: "Organization",
-) -> "UserQuerySet":
+) -> typing.List["User"]:
     """
     This method returns a sequence of `User` objects, filtered by users whose username, or case-insensitive e-mail,
-    is present in `usernames_from_ical`. If `include_viewers` is set to `True`, users are further filtered down
-    based on their granted permissions.
+    is present in `usernames_from_ical`.
 
     Parameters
     ----------
@@ -80,24 +79,26 @@ def users_in_ical(
     organization : apps.user_management.models.organization.Organization
         The organization in question
     """
-    from apps.user_management.models import User
+    required_permission = RBACPermission.Permissions.SCHEDULES_WRITE
 
     emails_from_ical = [username.lower() for username in usernames_from_ical]
 
-    # users_found_in_ical = organization.users
     users_found_in_ical = organization.users.filter(
-        **User.build_permissions_query(RBACPermission.Permissions.SCHEDULES_WRITE, organization)
-    )
-
-    users_found_in_ical = users_found_in_ical.filter(
         (Q(username__in=usernames_from_ical) | Q(email__lower__in=emails_from_ical))
     ).distinct()
 
-    return users_found_in_ical
+    if organization.is_rbac_permissions_enabled:
+        # it is more efficient to check permissions on the subset of users filtered above
+        # than performing a regex query for the required permission
+        users_found_in_ical = [u for u in users_found_in_ical if {"action": required_permission.value} in u.permissions]
+    else:
+        users_found_in_ical = users_found_in_ical.filter(role__lte=required_permission.fallback_role.value)
+
+    return list(users_found_in_ical)
 
 
 @timed_lru_cache(timeout=100)
-def memoized_users_in_ical(usernames_from_ical: typing.List[str], organization: "Organization") -> UserQuerySet:
+def memoized_users_in_ical(usernames_from_ical: typing.List[str], organization: "Organization") -> typing.List["User"]:
     # using in-memory cache instead of redis to avoid pickling python objects
     return users_in_ical(usernames_from_ical, organization)
 
@@ -354,7 +355,7 @@ def list_users_to_notify_from_ical_for_period(
     schedule: "OnCallSchedule",
     start_datetime: datetime.datetime,
     end_datetime: datetime.datetime,
-) -> UserQuerySet:
+) -> typing.List["User"]:
     users_found_in_ical: typing.Sequence["User"] = []
     events = schedule.final_events(start_datetime, end_datetime)
     usernames = []

engine/apps/user_management/migrations/0015_auto_20230926_2203.py

@@ -0,0 +1,21 @@
+# Generated by Django 3.2.20 on 2023-09-26 22:03
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('user_management', '0014_auto_20230728_0802'),
+    ]
+
+    operations = [
+        migrations.AddIndex(
+            model_name='user',
+            index=models.Index(fields=['is_active', 'organization', 'username'], name='user_manage_is_acti_385fc4_idx'),
+        ),
+        migrations.AddIndex(
+            model_name='user',
+            index=models.Index(fields=['is_active', 'organization', 'email'], name='user_manage_is_acti_7e930d_idx'),
+        ),
+    ]

engine/apps/user_management/models/user.py

@@ -169,6 +169,10 @@ class User(models.Model):
         # Including is_active to unique_together and setting is_active to None allows to
         # have multiple deleted users with the same user_id, but user_id is unique among active users
         unique_together = ("user_id", "organization", "is_active")
+        indexes = [
+            models.Index(fields=["is_active", "organization", "username"]),
+            models.Index(fields=["is_active", "organization", "email"]),
+        ]
 
     public_primary_key = models.CharField(
         max_length=20,