Re: Repeated $set's in oplog - bug?

[William Zola]

Marc -- when you look at these, are the values in the '$push' field the same, or different?

If they're different, then they are actually separate operations.  The repeated $sets are probably an artifact of how MongoDB tries to make the operations in the oplog idempotent.

 -William 

On Friday, October 26, 2012 2:16:11 PM UTC-7, Marc Tinkler wrote:

Hello, 

While looking at our oplog today, I noticed that many operations contain many (sometimes 15 in a row) duplicated $set objects. 

Does anyone know the reason for all the duplicated "$set"s? Is there something we are doing that can cause this, or is this just mongo weirdness?

Here's an example:

{

        "ts" : Timestamp(1351284504000, 1),

        "h" : NumberLong("4032111326304880614"),

        "op" : "u",

        "ns" : "thinkmap.gamesession",

        "o2" : {

                "_id" : "7BC81796-E180-46D4-9358-C8117251FE11",

                "ans" : {

                        "$size" : 12

                }

        },

        "o" : {

                "$set" : {

                        "ab" : 7.939708709716797

                },

                "$push" : {

                        "ans" : {

                                "qid" : 176635,

                                "ab" : 7.939708709716797,

                                "a" : 3,

                                "ts" : ISODate("2012-10-26T20:48:24.768Z"),

                                "pts" : 0,

                                "t" : "L",

                                "syn" : 110083,

                                "wrd" : "morbid",

                                "m" : "a",

                                "hnt" : false,

                                "c" : false

                        }

                },

                "$set" : {

                        "ab" : 7.939708709716797

                },

                "$set" : {

                        "ab" : 7.939708709716797

                },

                "$set" : {

                        "ab" : 7.939708709716797

                }

        }

}

Thanks,

Marc