import * as Knex from "knex";
import { Maybe } from "./util-types";
/**
 * String constants representing database clients supported by Knex.
 * This collection must be kept in sync with Knex.
 *
 * TODO: Expose this collection from knex itself.
 */
export declare const KNEX_SUPPORTED_DBS: string[];
/**
 * Subset of KNEX_SUPPORTED_DBS which are officially supported by GRelDAL and which are covered by GRelDAL's test coverage
 */
export declare const OFFICIALLY_SUPPORTED_DBS: string[];
/**
 * Singleton database connector used by default if a local database connector is not specified at data source level
 */
export declare let globalConnector: Maybe<Knex>;
/**
 * Validate if the passed knex connector is configured to use a supported datbase.
 */
export declare const assertSupportedConnector: (connector: Knex<any, unknown[]>) => Knex<any, unknown[]>;
export declare const assertConnectorConfigured: (connector?: Maybe<Knex<any, unknown[]>>) => Knex<any, unknown[]>;
/**
 * Register a database connector as the global default for the library.
 *
 * Connector options can be found in [knex documentation](https://knexjs.org/#Installation-client).
 *
 * @api-category PrimaryAPI
 */
export declare const useDatabaseConnector: (connector: Knex<any, unknown[]>) => Knex<any, unknown[]>;
/** Specify whether the database supports returning clause */
export declare const supportsReturning: (connector: Knex<any, unknown[]>) => boolean;