/**
 * Postgres-backed CheckpointStorage adapter.
 *
 * Provides production-grade persistence using Postgres with safe transactions
 * and best-effort recovery for corrupted rows.
 */
import type { Pool } from 'pg';
import type { CheckpointStorage, Checkpoint, CheckpointStatus } from './types';
/**
 * Configuration options for PostgresCheckpointStorage.
 */
export interface PostgresCheckpointStorageOptions {
    /**
     * Connection string for Postgres (e.g., postgres://user:pass@host:5432/db).
     * Either connectionString or pool must be provided.
     */
    connectionString?: string;
    /**
     * Pre-configured Pool instance for dependency injection (useful for testing).
     * Either connectionString or pool must be provided.
     */
    pool?: Pool;
}
/**
 * Postgres-backed implementation of CheckpointStorage.
 *
 * Features:
 * - Lazy schema initialization with CREATE TABLE IF NOT EXISTS
 * - Transactional writes for data integrity
 * - Best-effort recovery with warnings for corrupted rows
 * - Support for both connection string and injected pool (for testing)
 */
export declare class PostgresCheckpointStorage implements CheckpointStorage {
    private pool;
    private initialized;
    private initPromise;
    constructor(options: PostgresCheckpointStorageOptions);
    /**
     * Lazily initialize the database schema.
     * Safe to call multiple times; only executes once.
     */
    private ensureInitialized;
    private initializeSchema;
    /**
     * Save a checkpoint (upsert by run_id + step).
     */
    save(checkpoint: Checkpoint): Promise<void>;
    /**
     * Get the latest checkpoint for a run (highest step number).
     * Returns null if no checkpoints exist for the run.
     * Uses best-effort recovery, logging warnings for corrupted rows.
     */
    getLatest(runId: string): Promise<Checkpoint | null>;
    /**
     * Get a specific checkpoint by run_id and step.
     * Returns null if not found.
     */
    get(runId: string, step: number): Promise<Checkpoint | null>;
    /**
     * Update the status of a checkpoint.
     */
    updateStatus(runId: string, step: number, status: CheckpointStatus): Promise<void>;
    /**
     * Delete all checkpoints for a run.
     */
    deleteRun(runId: string): Promise<void>;
    /**
     * Delete expired checkpoints (where expires_at < NOW()).
     * @returns The number of deleted checkpoints
     */
    deleteExpired(): Promise<number>;
    /**
     * List checkpoints by status (for querying pending pauses).
     * Excludes expired checkpoints (where expires_at < NOW()).
     */
    listByStatus(status: CheckpointStatus): Promise<Checkpoint[]>;
    /**
     * Get the latest checkpoint for a pipeline (highest step, timestamp tie-break).
     * Returns the checkpoint with the highest step number, using created_at as a tie-breaker.
     * Excludes expired checkpoints.
     */
    getLatestByPipelineId(pipelineId: string): Promise<Checkpoint | null>;
    /**
     * Close the connection pool.
     */
    close(): Promise<void>;
    /**
     * Convert a database row to a Checkpoint object.
     */
    private rowToCheckpoint;
}
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