delete operator in db.collection.find().forEach() sometimes behaves incorrectly

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    • Type: Bug
    • Resolution: Done
    • Priority: Major - P3
    • None
    • Affects Version/s: 2.4.4, 2.4.8, 2.6.0-rc2
    • Component/s: JavaScript
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      here is a somewhat minimal test case;

      N=100

interpreterVersion() 

// setup data
db.coll.drop()
for (i = 0; i < N; i++) {
    newItem = {"a":1,"b":2}; 
    db.coll.insert(newItem);
}

// update
db.coll.find().forEach(function (obj) {
    obj.map = {
        "a":obj.a,
        "b":obj.b
        };
    delete obj.a;
    delete obj.b;
    db.coll.save(obj);
});


// check
db.coll.aggregate( { $group :
                         { _id : "$map.a",
                           totalA : { $sum : "$map.b" } 
                         }
                    });

      results:

       
// when  N = 100
// ok

{
    "result" : [ 
        {
            "_id" : 1,
            "totalA" : 200
        }
    ],
    "ok" : 1
}

      and fail

      // when N = 1000
// error, should be no undefined
{
	"result" : [
		{
			"_id" : null,
			"totalA" : 0
		},
		{
			"_id" : 1,
			"totalA" : 400
		}
	],
	"ok" : 1
}
      Show
      here is a somewhat minimal test case; N=100 interpreterVersion() // setup data db.coll.drop() for (i = 0; i < N; i++) { newItem = { "a" :1, "b" :2}; db.coll.insert(newItem); } // update db.coll.find().forEach(function (obj) { obj.map = { "a" :obj.a, "b" :obj.b }; delete obj.a; delete obj.b; db.coll.save(obj); }); // check db.coll.aggregate( { $group : { _id : "$map.a" , totalA : { $sum : "$map.b" } } }); results: // when N = 100 // ok { "result" : [ { "_id" : 1, "totalA" : 200 } ], "ok" : 1 } and fail // when N = 1000 // error, should be no undefined { "result" : [ { "_id" : null , "totalA" : 0 }, { "_id" : 1, "totalA" : 400 } ], "ok" : 1 }
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      Hi,

      I'm using db.collection.find().forEach()
      to modify collection, rearranging fields inside,
      also using 'delete obj.property'.

      and depending on collection size, when it grows larger than
      some small threshold, (in my tests 1000),
      some fields of modified objects are set to undefiend as result, istead of actual numbers.

      i was able to reproduce it in both
      MongoDB version: 2.4.4, 2.4.8, 2.6.0-rc2

            Assignee:
            Kamran K. (Inactive)
            Reporter:
            Vladimir Shakhov
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            Watchers:
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              Created:
              Updated:
              Resolved: