import { Heap } from "heap-js";
import { TupleKey } from "../lib/tupleKey.js";
import { PointSet } from "./zigzag.js";
type HeapEntry = {
    tuple: TupleKey;
    stream: PointSet;
};
export declare class Union implements PointSet {
    private streams;
    private heap?;
    constructor(streams: Array<PointSet>);
    initializeHeap(): Promise<Heap<HeapEntry>>;
    current(): Promise<TupleKey | null>;
    advance(): Promise<TupleKey | null>;
    seek(tuple: TupleKey): Promise<void>;
    sizeHint(): Promise<number>;
    setPrefetch(prefetch: number): void;
}
export {};
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