/**
 * Thrown when code running inside a transaction asks for a connection from the
 * pool whose only connection that transaction already holds. Waiting can never
 * succeed, so the caller gets this immediately instead of after every acquire
 * timeout and retry. It is deliberately not a connection error: retrying a
 * deadlock only repeats it.
 */
export declare class DbPoolSelfDeadlockError extends Error {
    readonly code = "DB_POOL_SELF_DEADLOCK";
    constructor(operation: string);
}
/** Marks `run`, and everything it awaits, as holding `pool`'s connection. */
export declare function runHoldingPoolConnection<T>(pool: object | undefined, run: () => T): T;
/**
 * TRAP: only a pool that provably has one connection can deadlock itself. A
 * pool whose size is unreadable is left to the acquire timeout rather than
 * failed on a guess.
 */
export declare function assertPoolConnectionAvailable(pool: object, operation: string): void;