Question

I am using meteor to make a query( for a publication) to find all the Results generated by Workers which has finished their work:

Results has the following structure:

result example 1:
{
  _id: "sldf234sdf"
  result_a:0,
  result_b:0
}

result example 2:
{
  _id: "ghjwef23qql"
  result_a:0,
  result_b:0
}

Workers is defined as:

{
  _id: "iweyr23s"
  results:["sldf234sdf", "ghjwef23qql"], //here is a list of 
  tag:'running'
}

Here is what I am trying to do:

// 1), I want to find all the workers which is finished with their tag
const workers = Workers.find({tag:'done'});

// 2), I want to get the resultid arrays in all the workers, then combine it into a big array
const results_id_arrays = workers[0].results + workers[1].results + ...

const results = Results.find({_id:{$in: results_id_arrays }});

So, my question is, how to make a mongodb query to implement the second step?

Answer 1

你可以使用强大的underscorejs。还有一个流星包。查看文档here。

//fetch results
const workers = Workers.find({tag:'done'}, {results: 1, _id: 0}).fetch();
//pluck only the ids, without field name
const plucked = _.pluck(workers, 'results');

//use plucked ids to find results
return Results.find({_id:{$in: plucked }});

Answer 2

这是你在找什么？

你可以得到这样的结果ID：

const results_id_arrays = Workers.aggregate({$project:{a:'$results'}},
                         {$unwind:'$a'},
                         {$unwind:'$a'},
                         {$group:{_id:'a',res:{$addToSet:'$a'}}}).map(function(e) {return e.res})

然后

const results = Results.find({_id:{$in: results_id_arrays }});

这有用吗？

Mongodb/Meteor: combine documents with ids in many arrays(returned by another query)

2 个答案: