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尝试使用monbro:mongodb-mapreduce-aggregation来运行一个超级简单的 mapReduce 函数。虽然它第一次很好用，但随后的调用我收到以下错误：

I20150608-11:11:05.294(-4)? Exception while invoking method 'exportDonations' Error: A method named '/donation_totals_by_donor/insert' is already defined
I20150608-11:11:05.294(-4)?     at packages/ddp/livedata_server.js:1461:1
I20150608-11:11:05.294(-4)?     at Function._.each._.forEach (packages/underscore/underscore.js:113:1)
I20150608-11:11:05.294(-4)?     at [object Object]._.extend.methods (packages/ddp/livedata_server.js:1459:1)
I20150608-11:11:05.294(-4)?     at [object Object].Mongo.Collection._defineMutationMethods (packages/mongo/collection.js:904:1)
I20150608-11:11:05.294(-4)?     at new Mongo.Collection (packages/mongo/collection.js:209:1)
I20150608-11:11:05.295(-4)?     at [object Object].ns.Collection (packages/matb33:collection-hooks/collection-hooks.js:190:1)
I20150608-11:11:05.295(-4)?     at [object Object].Meteor.methods.exportDonations (app/server/index.js:44:19)
I20150608-11:11:05.295(-4)?     at [object Object].methodMap.(anonymous function) (packages/meteorhacks:kadira/lib/hijack/wrap_session.js:160:1)
I20150608-11:11:05.295(-4)?     at maybeAuditArgumentChecks (packages/ddp/livedata_server.js:1617:1)
I20150608-11:11:05.295(-4)?     at packages/ddp/livedata_server.js:648:1

这是我的流星方法：

var Reduced = new Mongo.Collection("donation_totals_by_donor");

    var map = function() {
      if(!this.donor) {
        return;
      }

      emit(this.donor, this.amount);
    }

    var reduce = function(donorId, totalAmount) {
      return Array.sum(totalAmount);
    }

    var result = Donations.mapReduce(
                  map,
                  reduce,
                  {
                    query: { createdAt: { $gte: new Date('Jan 1, ' + year), $lt: new Date('Jan 1, ' + (year + 1)) } },
                    out: "donation_totals_by_donor",
                    verbose: true
                  }
                 );

    return Reduced.find({}).fetch();
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1 回答 1

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此错误是多次定义您的集合的结果。您需要将new Mongo.Collection代码移到方法之外。

通常你会在一个中心位置定义你的集合，例如lib/collections/mycollection.js. 但是，由于此代码仅在服务器上运行，您可以将其保留在此文件的顶部或将其放在类似server/collections/reduced.js.

于 2015-06-08T17:31:52.130 回答