fix(orb): index orb_relay_pending by created_at so the relay-drain prune stops full-scanning

[bitfathers94]

Summary

• pruneRelayPending runs on every pull-mode relay-drain (POST /v1/orb/relay/pull, fleet-wide, every 30s) and filters orb_relay_pending by a bare created_at predicate. Both existing indexes lead with installation_id, so neither can serve it — the SELECT and DELETE full-scan the table and can exceed the pull request's AbortSignal.timeout(30_000) budget, surfacing as the recurring TimeoutError in Sentry since 2026-07-15.
• Adds a (created_at, delivery_id) index (idx_orb_relay_pending_created_at) — declared in src/db/schema.ts and created in migrations/0167_orb_relay_pending_created_at_index.sql. It turns both the SELECT (WHERE created_at < ? ORDER BY created_at, delivery_id) and the DELETE (WHERE created_at < ?) into index range scans, and lets the SELECT satisfy its ORDER BY from the index with no temp-B-tree sort.

Closes #7430

Scope

• The PR title follows type(scope): short summary Conventional Commit format.
• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked a currently open issue this PR resolves (Closes #7430).

Validation

• git diff --check
• npm run db:migrations:check (contiguous 0001..0167, no new duplicates)
• npm run db:schema-drift:check (schema.ts matches migrations/)
• npm run typecheck
• New regression test test/unit/orb-relay-pending-index.test.ts asserts the index exists and that both of pruneRelayPending's queries EXPLAIN QUERY PLAN as a SEARCH via idx_orb_relay_pending_created_at (not a SCAN, and with no temp-B-tree sort). It fails before this change (full scan) and passes after.
• test/integration/orb-relay.test.ts (83 tests) still green.
• codecov/patch: the only measured diff line is the schema.ts index declaration, executed at module import like its sibling index declarations; the migration and test files are not coverage-measured.

Safety

• No secrets, wallet details, hotkeys, coldkeys, PATs, private keys, trust scores, or private evidence exposed.
• Pure DB-index change: no behavior change to query results, only their access path — existing relay tests confirm identical outcomes.

Notes

• The index mirrors the SELECT's ORDER BY (created_at, delivery_id) column order so the drain prune needs neither a full scan nor a sort step.

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.35%. Comparing base (25decd9) to head (64d518b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7451   +/-   ##
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  Coverage   91.35%   91.35%           
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  Files         716      716           
  Lines       72990    72990           
  Branches    21628    21627    -1     
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  Hits        66678    66678           
  Misses       5272     5272           
  Partials     1040     1040           

Flag	Coverage Δ
shard-1	33.69% <ø> (+1.01%)	⬆️
shard-2	40.35% <ø> (+4.23%)	⬆️
shard-3	28.76% <ø> (-5.77%)	⬇️
shard-4	39.57% <ø> (-3.32%)	⬇️
shard-5	35.72% <ø> (-1.25%)	⬇️
shard-6	34.83% <ø> (+1.28%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/db/schema.ts	72.97% <ø> (ø)

[loopover-orb]

Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-20 11:02:40 UTC}

3 files · 1 AI reviewer · no blockers · readiness 100/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
Adds a (created_at, delivery_id) index on orb_relay_pending and a matching migration, correctly turning pruneRelayPending's SELECT and DELETE from full scans into index range scans, with the SELECT also satisfying its ORDER BY from the index without a temp B-tree sort. The migration is additive (CREATE INDEX IF NOT EXISTS), schema.ts and the migration file agree on column order, and the new unit test directly asserts SEARCH-not-SCAN via EXPLAIN QUERY PLAN against the real queries used in orb/relay.ts, which is a solid regression test tied to the actual production path rather than a fabricated one.

Nits — 4 non-blocking

• The `sqlite_master` reference in test/unit/orb-relay-pending-index.test.ts:8 is SQLite's actual system table name, so it can't be renamed without breaking the query — the external brief's suggestion to replace it doesn't apply here.
• src/db/schema.ts is flagged as a large file (~888 lines) by the size-smell scan, but this diff only adds 4 lines to an existing table definition, so it's pre-existing size, not something introduced here.
• Confirm idx_orb_relay_pending_created_at is picked up by the existing `db:schema-drift:check` in CI (already checked per the PR description) so future schema edits stay in sync.
• Consider also asserting index cardinality/row-count behavior in the new test (e.g. planner picks the index even with a non-trivial row count) if SQLite's planner ever needs ANALYZE stats to prefer it over a table scan in production-sized tables.

Decision drivers

• ✅ Code review — No blockers (1 reviewer)
• ✅ Gate result — Passing (No configured blocker found.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	✅ Linked	#7430
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 45 registered-repo PR(s), 29 merged, 0 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	bitfathers94; Gittensor profile; 45 PR(s), 0 issue(s).
Improvement	✅ Minor	risk: clean · value: minor · LLM: moderate

Linked issue satisfaction

Addressed
The PR adds a (created_at, delivery_id) index in both the migration and schema.ts that directly targets the bare created_at predicate used by pruneRelayPending's SELECT and DELETE, matching the issue's root-cause diagnosis, and includes a regression test verifying EXPLAIN QUERY PLAN shows an index SEARCH rather than a SCAN.

Review context

• Author: bitfathers94
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 45 PR(s), 0 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Keep the PR focused and include validation evidence before maintainer review.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

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_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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[loopover-orb]

LoopOver is closing this pull request on the maintainer's behalf (Linked issue #7430 is assigned to the maintainer (@JSONbored) — that work is reserved for the maintainer, so this PR cannot be auto-accepted.). This is an automated maintenance action — to pursue this change, please open a new pull request with the issues resolved. Closed PRs may be analyzed later to improve review accuracy, but they are not automatically reopened or re-reviewed.