Mongoose操作挂起：深入理解连接状态与事件处理

// Check the connection to the database
console.log("Connection state: ", connection.readyState); // 输出 Connection state: 1
// Wait for the connection to be established
connection.once('connected', async () => {
  // ... 数据库操作 ...
  await connection.dropCollection('mdprodcats');
  // ...
});

const axios = require("axios");
const XLSX = require("xlsx");
const fs = require("fs");
const path = require("path");
const mongoose = require("mongoose");
// 假设 '../../../config/connection' 导出了 Mongoose Connection 实例
const connection = require("../../../config/connection");
const MdProdCat = require("../../../models/MdProdCat");

(async () => {
  try {
    console.log("=== Commencing MD Product Category import...");

    // 文件下载、保存、转换等操作 (与数据库无关，保持不变)
    console.log("Downloading .xlsx file...");
    const response = await axios.get(
      "https://assets.mydeal.com.au/content/marketplace/MyDeal_Product_Category_List.xlsx",
      { responseType: "arraybuffer" }
    );
    const xlsxFilePath = path.join(__dirname, "MyDeal_Product_Category_List.xlsx");
    fs.writeFileSync(xlsxFilePath, Buffer.from(response.data));
    console.log("Saved .xlsx file");

    console.log("Converting .xlsx to .csv...");
    const workbook = XLSX.read(response.data, { type: "buffer" });
    const sheetNameList = workbook.SheetNames;
    const csvData = XLSX.utils.sheet_to_csv(workbook.Sheets[sheetNameList[0]]);
    console.log("Converted .xlsx to .csv");

    console.log("Converting .csv to JSON...");
    const rows = csvData.split("\n").slice(1);
    const json = rows
      .filter((line) => line.trim())
      .map((line) => {
        const [CategoryID, Breadcrumbs] = line.split(",");
        return { _id: parseInt(CategoryID), Breadcrumbs };
      });
    console.log("Converted .csv to JSON");

    // 检查连接状态 (可选，但有助于调试)
    console.log("Connection state: ", connection.readyState);

    // 直接执行数据库操作，因为连接已经就绪
    try {
      console.log("Dropping collection if it already exists");
      // 注意：connection.db.dropCollection() 是更推荐的方式
      // connection.dropCollection() 是 Mongoose 5.x 引入的便捷方法，底层也是调用 db 实例
      await connection.db.dropCollection('mdprodcats');
      console.log("Collection dropped successfully");
    } catch (error) {
      // 'ns not found' 是 MongoDB 在集合不存在时抛出的错误码
      if (error.codeName === 'NamespaceNotFound' || error.message === 'ns not found') {
        console.log('Collection does not exist. Continuing...');
      } else {
        throw error;
      }
    }

    console.log("Inserting data...");
    await MdProdCat.insertMany(json);
    console.log("Data inserted successfully");

    console.log("Closing connection...");
    await connection.close();
    console.log("Connection closed");
    console.log("=== Import completed successfully");

    process.exit(0); // 正常退出
  } catch (error) {
    console.error("An error occurred:", error);
    process.exit(1); // 异常退出
  }
})();