ref(crons): Remove monitor from the check-in model

[wedamija]

Part of a series reducing crons database work per check-in, as check-in volume grows.

Removes monitor from the MonitorCheckIn model along with its two indexes, (monitor, date_added, status) (~75 GB) and (monitor, status, date_added) (~59 GB). The migration drops the indexes with DROP INDEX CONCURRENTLY and uses SafeRemoveField with MOVE_TO_PENDING, so the column stays until the next PR.

Do not merge until #127644 has deployed.

[github-actions]

This PR has a migration; here is the generated SQL for src/sentry/monitors/migrations/0020_make_checkin_monitor_nullable.py src/sentry/monitors/migrations/0021_remove_checkin_monitor.py

for 0020_make_checkin_monitor_nullable in monitors

--
-- Alter field monitor on monitorcheckin
--
SET CONSTRAINTS "sentry_monitorcheckin_monitor_id_c15ff0f0_fk_sentry_monitor_id" IMMEDIATE; ALTER TABLE "sentry_monitorcheckin" DROP CONSTRAINT "sentry_monitorcheckin_monitor_id_c15ff0f0_fk_sentry_monitor_id";
ALTER TABLE "sentry_monitorcheckin" ALTER COLUMN "monitor_id" DROP NOT NULL;

for 0021_remove_checkin_monitor in monitors

--
-- Remove index sentry_moni_monitor_0a49ce_idx from monitorcheckin
--
DROP INDEX CONCURRENTLY IF EXISTS "sentry_moni_monitor_0a49ce_idx";
--
-- Remove index sentry_moni_monitor_7ed5ce_idx from monitorcheckin
--
DROP INDEX CONCURRENTLY IF EXISTS "sentry_moni_monitor_7ed5ce_idx";
--
-- Moved monitorcheckin.monitor field to pending deletion state
--
-- (no-op)

[sentry]

Sentry Snapshot Testing

Name	Added	Removed	Changed	Renamed	Unchanged	Skipped	Status
sentry-frontend sentry-frontend	0	0	0	0	630	0	✅ Unchanged

⚙️ sentry-frontend Snapshot Settings

[github-actions]

This PR has a migration; here is the generated SQL for src/sentry/monitors/migrations/0021_make_checkin_monitor_nullable.py src/sentry/monitors/migrations/0022_remove_checkin_monitor.py

for 0021_make_checkin_monitor_nullable in monitors

--
-- Alter field monitor on monitorcheckin
--
SET CONSTRAINTS "sentry_monitorcheckin_monitor_id_c15ff0f0_fk_sentry_monitor_id" IMMEDIATE; ALTER TABLE "sentry_monitorcheckin" DROP CONSTRAINT "sentry_monitorcheckin_monitor_id_c15ff0f0_fk_sentry_monitor_id";
ALTER TABLE "sentry_monitorcheckin" ALTER COLUMN "monitor_id" DROP NOT NULL;

for 0022_remove_checkin_monitor in monitors

--
-- Remove index sentry_moni_monitor_0a49ce_idx from monitorcheckin
--
DROP INDEX CONCURRENTLY IF EXISTS "sentry_moni_monitor_0a49ce_idx";
--
-- Remove index sentry_moni_monitor_7ed5ce_idx from monitorcheckin
--
DROP INDEX CONCURRENTLY IF EXISTS "sentry_moni_monitor_7ed5ce_idx";
--
-- Moved monitorcheckin.monitor field to pending deletion state
--
-- (no-op)

[github-actions]

This PR has a migration; here is the generated SQL for src/sentry/monitors/migrations/0022_remove_checkin_monitor.py

for 0022_remove_checkin_monitor in monitors

--
-- Remove index sentry_moni_monitor_0a49ce_idx from monitorcheckin
--
DROP INDEX CONCURRENTLY IF EXISTS "sentry_moni_monitor_0a49ce_idx";
--
-- Remove index sentry_moni_monitor_7ed5ce_idx from monitorcheckin
--
DROP INDEX CONCURRENTLY IF EXISTS "sentry_moni_monitor_7ed5ce_idx";
--
-- Moved monitorcheckin.monitor field to pending deletion state
--
-- (no-op)

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 9e329c3. Configure here.}

[cursor]

Index drop not marked post-deployment

Medium Severity

Setting is_post_deployment to False makes this migration run automatically during deploy. The two unused monitor indexes on MonitorCheckIn are about 75 GB and 59 GB, so dropping them inline can stall or fail the deploy instead of being applied later through the post-deployment path.

 

^{Reviewed by Cursor Bugbot for commit 9e329c3. Configure here.}