Add indexes on sp_action.rollout and rollout_group

[clayly]

Summary

Several rollout-monitoring queries on sp_action (existsByRolloutId, getStatusCountByRolloutId, getStatusCountByRolloutGroupId, etc.) filter by rollout or rollout_group. The flyway baseline does not index either column, so Postgres falls back to Seq Scan, scanning the entire sp_action table on every monitoring poll.

For a 16 k-device rollout this means 16 k action rows scanned per call, multiple times per second during dispatch and monitoring. Beyond a single rollout, the table grows over the lifetime of the deployment and the cost grows linearly.

Fix

Two composite indexes:

• sp_idx_action_rollout_status on (tenant, rollout, status) — covers both filter and GROUP BY status patterns; enables Index Only Scan with no heap fetch
• sp_idx_action_rollout_group on (tenant, rollout_group) — covers rollout_group=? lookups (Hibernate-generated SQL always includes tenant via the multi-tenant filter)

V1_20_2__action_rollout_indexes migrations added for POSTGRESQL, H2, and MYSQL.

Idempotency

Each migration is guarded so re-applying the SQL against a schema that already has the index is a no-op:

• PostgreSQL and H2: CREATE INDEX IF NOT EXISTS
• MySQL ≤ 8.x has no native IF NOT EXISTS for CREATE INDEX, so the migration uses an INFORMATION_SCHEMA lookup with PREPARE/EXECUTE. MariaDB and MySQL behave identically here.

This protects deployments that may already have created these indexes out-of-band (e.g. via a fork's repeatable migration, an operator hot-fix, or a re-run after a failed migration).

Performance evidence

Insert 16 000 rows into sp_action tied to rollout=1, spread across rollout_group=1..17. Run the hot queries 1000 times each, before and after the indexes.

PostgreSQL 16

query	no index	with index	speedup
WHERE tenant=? AND rollout=? GROUP BY status	1.256 s	0.504 s	2.5x
WHERE tenant=? AND rollout_group=? count	0.501 s	0.027 s	18.6x
WHERE rollout=? LIMIT 1 (exists)	1.5 µs	1.4 µs	1x (early-out)

Plans switch from Seq Scan to Index Only Scan, Heap Fetches: 0. Buffer reads drop from 214 → 17 (12x).

YugabyteDB (PostgreSQL-compatible YSQL)

query	no index	with index	speedup
WHERE tenant=? AND rollout=? GROUP BY status	4.146 s	2.841 s	1.5x
WHERE tenant=? AND rollout_group=? count	2.595 s	0.148 s	17.6x
WHERE rollout=? LIMIT 1 (exists)	21 µs	21 µs	1x (early-out)

Plain PG syntax works on YB. The leading column gets HASH-partitioned across tablets by default, optimal for the equality-on-tenant access pattern. Index Only Scan is supported on YB with Heap Fetches: 0.

YB seq scans are 3–5x slower than PG seq scans (network round-trip per page across tablets), so the index is even more critical on a YugabyteDB deployment.

Test plan

• Schema migration applies cleanly on H2, PostgreSQL and YugabyteDB
• Re-applying migration against a schema that already has the indexes is a no-op
• EXPLAIN confirms Index Only Scan after migration
• Long-running rollout test (1 k+ targets) before/after — measure UI rollout-detail responsiveness

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