/**
 * Delta-polling helpers for the v-next Postgres observability domain.
 *
 * Cursor model
 * ------------
 * Each signal table stores both:
 *   - `xactId xid8 DEFAULT pg_current_xact_id()`
 *   - `cursorId bigserial`
 *
 * `bigserial` values are allocated before commit, so a later `cursorId` can
 * become visible before an earlier one. Delta reads therefore order by the
 * pair `(xactId, cursorId)` and cap reads at PostgreSQL's safe transaction
 * horizon: `pg_snapshot_xmin(pg_current_snapshot())`. Rows with `xactId`
 * below that horizon cannot still be in flight, so advancing the cursor there
 * cannot skip a late-committing row.
 */
import type { DbClient } from '../../../client.js';
export declare const OBSERVABILITY_DELTA_POLLING_FEATURE = "observability-delta-polling";
export declare function deltaPollingFeatureEnabled(): boolean;
export declare function assertDeltaPollingEnabled(): void;
export interface DeltaCursorParts {
    xactId: string;
    cursorId: string;
}
export declare function encodeDeltaCursor(xactId: unknown, cursorId?: unknown): string;
export declare function decodeDeltaCursor(cursor: string): DeltaCursorParts;
export declare function readSafeXactHorizon(client: DbClient): Promise<string>;
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