fix(cohorts): Drop redundant cohortcalculationhistory indexes

[dustinbyrne]

This change drops some unused/redundant indexes on posthog_cohortcalculationhistory.

We currently have:

"posthog_cohortcalculationhistory_pkey" PRIMARY KEY, btree (id)
"posthog_coh_cohort__cbac1b_idx" btree (cohort_id, started_at DESC)
"posthog_coh_team_id_0ba00c_idx" btree (team_id, cohort_id)
"posthog_coh_team_id_762cc7_idx" btree (team_id, started_at)
"posthog_cohortcalculationhistory_cohort_id_e7c02b55" btree (cohort_id)
"posthog_cohortcalculationhistory_team_id_beba9c96" btree (team_id) 

posthog_cohortcalculationhistory_cohort_id_e7c02b55 indexes cohort_id, but so does the composite index posthog_coh_cohort__cbac1b_idx.
posthog_cohortcalculationhistory_team_id_beba9c96 indexes team_id, but so do the composite indexes posthog_coh_team_id_0ba00c_idx and posthog_coh_team_id_762cc7_idx.

This change drops posthog_cohortcalculationhistory_cohort_id_e7c02b55, posthog_cohortcalculationhistory_team_id_beba9c96.

[github-actions]

Migration SQL Changes

Hey 👋, we've detected some migrations on this PR. Here's the SQL output for each migration, make sure they make sense:

posthog/migrations/0937_remove_redundant_cohortcalculationhistory_indexes.py

--
-- Raw SQL operation
--
DROP INDEX CONCURRENTLY IF EXISTS posthog_cohortcalculationhistory_cohort_id_e7c02b55;
--
-- Raw SQL operation
--
DROP INDEX CONCURRENTLY IF EXISTS posthog_cohortcalculationhistory_team_id_beba9c96;

Last updated: 2025-12-08 21:36 UTC (b50450e)

[github-actions]

🔍 Migration Risk Analysis

We've analyzed your migrations for potential risks.

Summary: 1 Safe | 0 Needs Review | 0 Blocked

✅ Safe

Brief or no lock, backwards compatible

posthog.0937_remove_redundant_cohortcalculationhistory_indexes
  └─ #1 ✅ RunSQL: DROP INDEX CONCURRENTLY is safe (non-blocking)
  └─ #2 ✅ RunSQL: DROP INDEX CONCURRENTLY is safe (non-blocking)

Last updated: 2025-12-08 21:36 UTC (b50450e)

[Copilot]

Pull request overview

This PR drops redundant database indexes on the posthog_cohortcalculationhistory table to reduce database overhead and improve performance. The indexes being removed are covered by existing composite indexes.

Key Changes:

• Drops single-column index on cohort_id (covered by composite index on cohort_id, started_at DESC)
• Drops single-column index on team_id (covered by composite indexes on team_id, cohort_id and team_id, started_at)

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
posthog/migrations/0936_remove_redundant_cohortcalculationhistory_indexes.py	Migration to drop two redundant indexes using DROP INDEX CONCURRENTLY for non-blocking database operation
posthog/migrations/max_migration.txt	Updated to track the latest migration number

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[greptile-apps]

_{2 files reviewed, no comments}

_{Edit Code Review Agent Settings | Greptile}