zkldi_Tachi/server/scripts/__KT_DATABASE_MIGRATION/migrate.ts

import CreateLogCtx from "lib/logger/logger";
import { ICollection } from "monk";
import { oldKTDB } from "./old-db";

const logger = CreateLogCtx(__filename);

const newDocuments: unknown[] = [];

export default async function MigrateRecords(
	existingCollection: ICollection,
	collectionName: string,
	HandlerFN: (c: unknown) => unknown
) {
	const existingRecords = await existingCollection.count({});
	logger.info(`Starting migration for ${collectionName}...`);

	if (existingRecords > 0) {
		logger.error(`${existingRecords} documents already exist in db, terminating.`);
		process.exit(1);
	}

	let i = 0;

	await oldKTDB
		.get(collectionName)
		.find({})
		// @ts-expect-error it exists.
		.each(async (c, { pause, resume }) => {
			i++;
			pause();

			if (i % 10000 === 0) {
				logger.info(`Processed ${i} documents.`);
			}
			const newDoc = await HandlerFN(c);

			if (newDoc !== null) {
				newDocuments.push(newDoc);
			}

			resume();
		});

	logger.info(`Inserting ${newDocuments.length} documents.`);
	await existingCollection.insert(newDocuments.flat());
	logger.info(`Done!`);

	process.exit(0);
}