fix: run cohortpeople count query without joins

[pl]

Problem

We join cohortpeople count queries with persons table to validate the team ID, which is super slow for large cohorts.

Changes

Changes the count query to run a separate query to check the team id.

How did you test this code?

Added a test to verify team isolation.

[greptile-apps]

_{2 files reviewed, 2 comments}

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[greptile-apps]

logic: Missing team_id filter in count query causes incorrect counts in multi-team projects.

When recalculate_cohortpeople runs for a project with multiple teams (environments), it calls this function for each team. The same cohort_id can have CohortPeople entries with different team_id values. Without filtering by team_id, all teams get the same total count instead of team-specific counts.

The ClickHouse table has team_id but the Django model doesn't expose it. Use raw SQL to filter properly:

Suggested change

	count = CohortPeople.objects.filter(cohort_id=cohort_id).count()
	# Then count cohortpeople filtering by team_id (in persons DB, no cross-DB join)
	result = sync_execute(
	f"SELECT count() FROM {PERSON_STATIC_COHORT_TABLE} WHERE cohort_id = %(cohort_id)s AND team_id = %(team_id)s",
	{"cohort_id": cohort_id, "team_id": team_id}
	)
	count = result[0][0] if result else 0

Prompt To Fix With AI

This is a comment left during a code review.
Path: posthog/models/cohort/util.py
Line: 428:428

Comment:
**logic:** Missing `team_id` filter in count query causes incorrect counts in multi-team projects.

When `recalculate_cohortpeople` runs for a project with multiple teams (environments), it calls this function for each team. The same `cohort_id` can have CohortPeople entries with different `team_id` values. Without filtering by `team_id`, all teams get the same total count instead of team-specific counts.

The ClickHouse table has `team_id` but the Django model doesn't expose it. Use raw SQL to filter properly:

```suggestion
    # Then count cohortpeople filtering by team_id (in persons DB, no cross-DB join)
    result = sync_execute(
        f"SELECT count() FROM {PERSON_STATIC_COHORT_TABLE} WHERE cohort_id = %(cohort_id)s AND team_id = %(team_id)s",
        {"cohort_id": cohort_id, "team_id": team_id}
    )
    count = result[0][0] if result else 0
```

How can I resolve this? If you propose a fix, please make it concise.

[greptile-apps]

logic: Test doesn't cover the multi-team-in-same-project scenario where the bug occurs.

The current test validates team isolation across different organizations, but doesn't test the case where multiple teams in the same project share a cohort. In recalculate_cohortpeople, all teams in a project get CohortPeople entries for the same cohort_id but with different team_id values.

Add a test case like:

# Create two teams in the same project
team2 = Team.objects.create(organization=self.organization, project_id=self.team.project_id)

# Add people to the cohort from both teams
cohort.insert_users_by_list(["person1_team1"], team_id=self.team.pk)
cohort.insert_users_by_list(["person1_team2"], team_id=team2.pk)

# Each team should see only their count
assert get_static_cohort_size(cohort_id=cohort.pk, team_id=self.team.pk) == 1
assert get_static_cohort_size(cohort_id=cohort.pk, team_id=team2.pk) == 1

Prompt To Fix With AI

This is a comment left during a code review.
Path: posthog/test/test_cohort_model.py
Line: 342:363

Comment:
**logic:** Test doesn't cover the multi-team-in-same-project scenario where the bug occurs.

The current test validates team isolation across different organizations, but doesn't test the case where multiple teams in the same project share a cohort. In `recalculate_cohortpeople`, all teams in a project get CohortPeople entries for the same `cohort_id` but with different `team_id` values.

Add a test case like:
```python
# Create two teams in the same project
team2 = Team.objects.create(organization=self.organization, project_id=self.team.project_id)

# Add people to the cohort from both teams
cohort.insert_users_by_list(["person1_team1"], team_id=self.team.pk)
cohort.insert_users_by_list(["person1_team2"], team_id=team2.pk)

# Each team should see only their count
assert get_static_cohort_size(cohort_id=cohort.pk, team_id=self.team.pk) == 1
assert get_static_cohort_size(cohort_id=cohort.pk, team_id=team2.pk) == 1
```

How can I resolve this? If you propose a fix, please make it concise.