/**
 * Migrations are used to update dataset structure as extension evolves.
 * Not every extension version requires a structure update.
 *
 * “Dataset extension”
 * generally means “extension version captured in dataset metadata”.
 *
 * A migration uses functions to retrieve deserialized object data
 * and generates serialized buffer data as a result.
 */
import type { BufferDataset } from './buffers';
import type { DatasetContext } from './renderer';
export interface DatasetMigrationOptions extends Pick<DatasetContext, 'getObjectData' | 'getMapReducedData'> {
    /** Current version of the dataset. */
    versionBefore?: string;
    onProgress?: (message: string, loaded?: number, total?: number) => void;
}
export interface MigrationInfo {
    /**
     * Version of the dataset to set after applying the migration.
     * Must not satisfy `versionBefore`, otherwise means infinite migration loop.
     *
     * This is ignored for initial migration, which is naturally expected
     * to migrate the dataset to extension version.
     */
    versionAfter: string;
    migrator: MigratorConstructor;
}
/**
 * Migrator function is a generator of buffer datasets
 * with dataset-relative paths. A path assigned to `null`
 * means buffer at that path will be deleted, if existed.
 */
export declare type Migrator = AsyncGenerator<BufferDataset, void, void>;
export declare type MigratorConstructor = (opts: DatasetMigrationOptions) => Migrator;