Java，MongoDB:如何在迭代庞大的集合时更新每个对象? [英] Java, MongoDB: How to update every object while iterating a huge collection?

问题描述

我收集了大约100万条记录，每个记录有20个字段.我需要更新每个记录(文档)中的整数flag字段，并随机分配1或2到此flag字段. 在游标遍历整个集合时如何执行此操作?似乎第二次搜索MongoDB已经找到的对象只是为了能够更新它，这似乎不是一个好主意:

I have a collection of about 1 million records with 20 fields each. I need to update integer flag field in every record (document) assigning randomly 1 or 2 to this flag field. How to do this while iterating cursor over the complete collection? It does not seem to be a good idea to search second time for object already found by MongoDB just to be able to update it:

  DBCursor cursor = coll.find();
  try {
     while(cursor.hasNext()) {
    BasicDBObject obj = (BasicDBObject) cursor.next();
    ...
    coll.update(query,newObj)

     }
  } finally {
     cursor.close();
  }

如何有效地更新巨大的MongoDB集合的每个文档中具有不同值的字段?

How to update a field in every document of a huge MongoDB collection with different values efficiently?

推荐答案

您的方法基本上是正确的. 但是，我不会将这样的集合视为巨大的" 您可以从shell运行类似的东西:

Your approach is basically correct. However I wouldn't consider such a collection as "huge" You can run something similar from the shell:

coll.find({}).forEach(function (doc) {
    doc.flag = Math.floor((Math.random()*2)+1);
    coll.save(doc);
 });

根据您的MongoDB版本，配置和负载，这可能需要几分钟到几小时的时间

Depending on your MongoDB version, configuration and load, this may take something between few minutes to several hours

如果要批量执行此更新，请在查询文档中使用某些条件，例如coll.find({"aFiled" : {$gt : minVal}, "aFiled" : {$lt : maxVal}})

If you want to perform this update in bulks, use some conditions in your query document, something such as coll.find({"aFiled" : {$gt : minVal}, "aFiled" : {$lt : maxVal}})

这篇关于Java，MongoDB:如何在迭代庞大的集合时更新每个对象?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！