您可以使用javascript API在GridFS上使用查找查询吗? [英] Can you use find queries on GridFS using javascript API?

问题描述

据我了解，当您在GridFS中输入内容时，它会被输入引擎盖下的2个不同的集合中.一种用于原始数据块，另一种用于元数据文件.

As I understand it, when you enter something into GridFS it gets entered into 2 different collections under the hood. One for the raw chunks of data and one for the meta data files.

据我从MongoDB文档中了解，您只能从GridFS中检索具有ID或名称的文档.

Also from what I understand from MongoDB's documentation is that you can only retrieve a document from GridFS with an id or name.

var gs = new mongodb.GridStore(db, "test.png", "w", {
"content_type": "image/png",
"metadata":{
    "author": "Daniel"
},
"chunk_size": 1024*4

});

那么，如果我想从GridFS中获取文档的子集怎么办?例如，如果我希望所有的GridStore具有:

So what if I want to get a subset of documents from GridFS? For example what if I want all GridStores with:

元数据:{作者:丹尼尔"}

metadata: {author: "Daniel"}

为什么我不能使用标准的mongo查询{field:somevalue}并以这种方式检索文档?

Why can't I use standard mongo queries { field: somevalue } and retrieve documents that way?

有人知道该怎么做吗?我在node.js上使用了javascript API.

Does anybody know how this can be done? I'm using the javascript API on node.js.

推荐答案

您可以像其他任何集合一样查询db.files集合:

You can query the db.files collection just like any other collection:

db.collection('fs.files')
  .find({ 'metadata.author' : 'Daniel' })
  .toArray(function(err, files) {
    if (err) throw err;
    files.forEach(function(file) {
      var gs = new mongodb.GridStore(db, file._id, 'r');
      ...
    });
  });

尽管您可能要使用 async.each forEach 或其他任何async.*方法.

Although instead of plain forEach you may want to use async.each or any of the other async.* methods.

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