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By: a guest on Jul 15th, 2012  |  syntax: None  |  size: 1.65 KB  |  hits: 13  |  expires: Never
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  1. Mongo DB MapReduce: Emit key from array based on condition
  2. {
  3.     "_id" : ObjectId("4fc5ed3e67960de6794dd21c"),
  4.     "name" : "some name",
  5.     "uid" : "some app specific uid",
  6.     "collection" : "some name",
  7.     "metadata" : [
  8.         {
  9.             "key" : "key1",
  10.             "value" : "Plain text",
  11.             "status" : "SINGLE_RESULT",
  12.         },
  13.         {
  14.             "key" : "key2",
  15.             "value" : "text/plain",
  16.             "status" : "SINGLE_RESULT",
  17.         },
  18.         {
  19.             "key" : "key3",
  20.             "value" : 3469,
  21.             "status" : "OK",
  22.         }
  23.      ]
  24. }
  25.        
  26. function map() {
  27.    var mime = "";
  28.    this.metadata.forEach(function (m) {
  29.      if (m.key === "key2") {
  30.         mime = m.value;}
  31.      });
  32.      emit(mime, {count:1});
  33. }
  34.  
  35. function reduce() {
  36.   var res = {count:0};
  37.   values.forEach(function (v) {res.count += v.count;});
  38.   return res;
  39. }
  40.  
  41. db.collection.mapReduce(map, reduce, {out: { inline : 1}})
  42.        
  43. {
  44.     "_id" : ObjectId("4fc5ed3e67960de6794dd21c"),
  45.     "name" : "some name",
  46.     "uid" : "some app specific uid",
  47.     "collection" : "some name",
  48.     "metadata" : {
  49.         "key1" : {
  50.             "value" : "Plain text",
  51.             "status" : "SINGLE_RESULT"
  52.         },
  53.         "key2": {
  54.             "value" : "text/plain",
  55.             "status" : "SINGLE_RESULT"
  56.         },
  57.         "key3" : {
  58.             "value" : 3469,
  59.             "status" : "OK"
  60.         }
  61.      }
  62. }
  63.        
  64. function map() {
  65.    emit( this.metadata["key2"].value, { count : 1 } );
  66. }
  67.        
  68. function map() {
  69.    var mime = "";
  70.    this.metadata.forEach(function (m) {
  71.      if (m.key === "key2") {
  72.         mime = m.value;
  73.         break;
  74.      }
  75.      });
  76.      emit(mime, {count:1});
  77. }
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