/**
 * Periodic compaction for the LanceDB-backed search indexes (change: bulletproof-background-index).
 *
 * Every incremental update is a `delete` + `add`, and LanceDB is append-only and versioned: each
 * one leaves the previous version and its data fragments on disk. Nothing reclaimed them. A full
 * `analyze` happens to clean up — it rebuilds the directory from scratch — but a machine that just
 * leaves the watcher running never gets there, which is exactly the "always on in the background"
 * case this tool is meant for.
 *
 * Measured on a real working repository whose SOURCE is about 9 MB, after a few weeks of watching:
 *
 * | index             | on disk | live rows | versions | after compaction |
 * |-------------------|---------|-----------|----------|------------------|
 * | `text-line-index` | 401 MB  | 234,267   | 953      | 36 MB            |
 * | `vector-index`    |  62 MB  |   8,372   | 952      | 14 MB            |
 *
 * Roughly 90% of what the tool had written was reclaimable garbage, and it grows without bound.
 *
 * Two deliberate choices:
 *
 *  - Compaction runs on a COUNTER, not every update. It costs a few hundred milliseconds on the
 *    indexes above, which is fine occasionally and is not fine on every keystroke-save.
 *  - Old versions are kept for {@link VERSION_GRACE_MS} rather than dropped outright. A reader
 *    that opened the table a moment ago is still pinned to the version it opened; `cleanupOlderThan:
 *    new Date()` would delete the files out from under it. The current version is never removed by
 *    LanceDB regardless, so the grace window only protects concurrent readers.
 */
/** Minimal view of the LanceDB table surface this module needs. */
interface CompactableTable {
    optimize(options?: {
        cleanupOlderThan?: Date;
        deleteUnverified?: boolean;
    }): Promise<unknown>;
}
/**
 * Record one incremental update against `dbPath`, and compact if enough have accumulated.
 *
 * Best-effort by construction: compaction is a space optimization, never a correctness
 * requirement, so a failure is swallowed and the counter still resets. The alternative — letting
 * an optimize error surface — would turn a disk-space chore into a failed file save.
 */
export declare function noteUpdateAndMaybeCompact(dbPath: string, table: CompactableTable): Promise<boolean>;
/** Test-only: lower the threshold so a small fixture reaches it. Returns the previous value. */
export declare function _setCompactEveryForTesting(n: number): number;
/** Test-only: shrink the reader-safety window so a fresh fixture can be reclaimed. */
export declare function _setVersionGraceMsForTesting(n: number): number;
/** Test-only: forget the counters so cases cannot leak into each other. */
export declare function _resetCompactionCountersForTesting(): void;
export {};
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