Collection-size index suggestions: review record

The executable implementation reviewed here is commit 64c79bd8 (parent ae2eb3fbf3a314a7f043f0d963fd336d8c1f1ec8). The raw report is issue #1700, including its non-blocking performance aside; it had no comments at evaluation time.

Law, reach, and observations

IndexDevModeConfig.collectionSizeThreshold documents size-based index suggestions, and the emitted message asks a developer to add a field index. For a queried source Collection over the threshold, advice is useful when the field is not indexed and the Collection does not create an index itself. It is redundant when autoIndex: 'eager' creates the matching index.

The bounded oracle in packages/db/tests/index-suggestion-oracle.test.ts uses a public filtered live-query Collection at initial readiness. Its model is the stated size/mode/matching-index rule. The history grammar crosses explicit manual mode, default manual mode, eager mode, 1,000 versus 1,101 rows, no/matching/unrelated index, and advice enabled/disabled. It checks the actual suggestion metadata, exact public result row, and index count. The unrelated-index control rejects a classifier that suppresses advice merely because some index exists.

On unchanged ae2eb3fb, the final oracle was RED in four of seven cells: explicit manual mode, default manual mode, and manual mode with an unrelated index each recorded zero suggestions where one was expected; eager mode recorded one where zero was expected. The threshold, matching-index, and disabled-advice controls passed. On 64c79bd8, all seven cells passed; the 17 existing auto-index tests passed, and package Vitest reported zero type errors. The change keeps the production file at 5 added versus 6 removed lines. The report's proposed single-guard inversion was insufficient because ensureIndexForExpression had its own manual-mode early return; the fix changes both gates.

Oracle guide audit

Requirement	Outcome
ORC-001	Public dev-mode configuration and suggestion message supply the policy; this owner limits itself to initial filtered-query readiness and size advice.
ORC-002	Expected advice follows the declarative size/mode/index rule, without importing production's guard or index-search helper.
ORC-003	Opening prose states the contract, model, grammar, driver, and checkpoint; expectedSuggestions and the public query assertions keep them visible.
ORC-004	Not triggered: the seven-cell matrix is bounded enumeration, not a generated-history coverage claim.
ORC-005	createLiveQueryCollection executes the reported WHERE path; the test checks public rows and captured IndexSuggestion metadata after readiness.
ORC-006	The actual pre-fix implementation fails at both intended advice assertions, demonstrating checker sensitivity.
ORC-007	Not triggered: no important generated property was added.
ORC-008	Not triggered: the model has no evolving reference state.
ORC-009	Not triggered: the model uses the Collection, row, index, and readiness concepts directly, with no combined lifecycle abstraction.
ORC-010	The fixed matrix does not shrink or capture asynchronous failures. Each fixture cleans up both Collections and reports assertion plus cleanup failures together, preserving the assertion as the cause.
ORC-011	No named plausible fault shared by production and this independent declarative advice rule requires a second formulation.
ORC-012	This record names the reviewed commit, RED/GREEN observations, controls, and limits. The bounded closure is manual/default/eager × initial filtered-query setup × public suggestion/index/result observations. It does not claim all query shapes, repeated warning volume, post-GC histories, slow-query timing, index work, or production-build execution.

The coverage map names the owner and remaining limits. The report's post-GC repetition was not separately executed; the fixed eager branch cannot emit a size suggestion regardless of whether cleanup cleared an index first. The report's timing figures remain background context, not a verified work law.