export interface Identifier {
    _id: string;
}
interface Operator<T> {
    $lt?: T;
    $lte?: T;
    $gt?: T;
    $gte?: T;
    $ne?: T;
    $in?: T[];
    $nin?: T[];
    $exists?: boolean;
    $regex?: RegExp;
}
interface LogicalOperator<T> {
    $and?: Array<Query<T>>;
    $or?: Array<Query<T>>;
    $not?: Query<T>;
    $where?: (this: T) => boolean;
}
/**
 * A query to select objects in database.
 */
export declare type Query<T> = Partial<T> | LogicalOperator<T> | {
    [P in keyof T]?: Operator<T[P]>;
};
/**
 * A projection for selected objects.
 */
export declare type Projection<T> = {
    [P in keyof T]?: 0 | 1;
};
interface UpdateOperator<T> {
    $set?: Partial<T>;
    $unset?: {
        [P in keyof T]?: true;
    };
    $inc?: Partial<T>;
    $min?: Partial<T>;
    $max?: Partial<T>;
}
/**
 * An update query.
 */
export declare type Update<T> = T | UpdateOperator<T>;
export {};