如何将 100 万条记录异步保存到 mongodb？

Question

我想使用 javascript 将 100 万条记录保存到 mongodb，如下所示：

for (var i = 0; i<10000000; i++) {
  model = buildModel(i);
  db.save(model, function(err, done) {
    console.log('cool');
  });
}

我试过了，它保存了~160条记录，然后挂了2分钟，然后退出了。为什么？

Answer 1

它失败了，因为您没有等待异步调用完成就可以继续进行下一次迭代。这意味着您正在构建一个 "stack" 未解决的操作，直到这导致问题为止。这个站点的名称又是什么？拿到照片了吗？

所以这不是继续 "Bulk" insertions. Fortunately the underlying MongoDB driver has already thought about this, aside from the callback issue mentioned earlier. There is in fact a "Bulk API" available to make this a whole lot better. And assuming you already pulled the native driver as the db object. But I prefer just using the .collection accessor from the model, and the "async" 模块使一切都清楚的最佳方法：

var bulk = Model.collection.initializeOrderedBulkOp();
var counter = 0;

async.whilst(
  // Iterator condition
  function() { return count < 1000000 },

  // Do this in the iterator
  function(callback) {
    counter++;
    var model = buildModel(counter);
    bulk.insert(model);

    if ( counter % 1000 == 0 ) {
      bulk.execute(function(err,result) {
        bulk = Model.collection.initializeOrderedBulkOp();
        callback(err);
      });
    } else {
      callback();
    }
  },

  // When all is done
  function(err) {
    if ( counter % 1000 != 0 ) 
        bulk.execute(function(err,result) {
           console.log( "inserted some more" );
        });        
    console.log( "I'm finished now" ;
  }
);

不同之处在于在完成时同时使用 "asynchronous" 回调方法，而不是仅仅建立一个堆栈，而且还使用 "Bulk Operations API" 以通过批量提交所有内容来减轻异步写入调用更新 1000 个条目的报表。

这不仅不像您自己的示例代码那样 "build up a stack" 执行函数，而且还执行高效的 "wire" 事务，因为不会将所有内容都发送到单独的语句中，而是分解成可管理的"batches" 用于服务器承诺。

Answer 2

你应该使用类似 Async's eachLimit:

// Create a array of numbers 0-999999
var models = new Array(1000000);
for (var i = models.length; i >= 0; i--)
  models[i] = i;

// Iterate over the array performing a MongoDB save operation for each item
// while never performing more than 20 parallel saves at the same time
async.eachLimit(models, 20, function iterator(model, next){
  // Build a model and save it to the DB, call next when finished
  db.save(buildModel(model), next);
}, function done(err, results){
  if (err) { // When an error has occurred while trying to save any model to the DB
    console.error(err);
  } else { // When all 1,000,000 models have been saved to the DB
    console.log('Successfully saved ' + results.length + ' models to MongoDB.');
  }
});

如何将 100 万条记录异步保存到 mongodb？

How to save 1 million records to mongodb asyncronously?

javascript

mongoose

mongodb

node.js

mongodb-query