How to insert sequence number after sort operation into mongoDB?

Question

I try to sort a collection by num_atoms wtih JS code:

db.zinc_data.find().sort({"num_atoms":-1}).forEach(function(mydoc){ 
    db2 = connect("database:port/zinc_Purtest_sort");
    db2.zinc_data.insert(mydoc);
})

mongos> db.zinc_data.find({}).pretty()
{ "_id" : ObjectId("586e3ac78426af7af1425655"), "num_atoms" : 76, "idxd" : 5 }
{ "_id" : ObjectId("586e3ac88426af7af14256b2"), "num_atoms" : 74, "idxd" : 89}
{ "_id" : ObjectId("586e3ac78426af7af1425666"), "num_atoms" : 66, "idxd" : 64}
{ "_id" : ObjectId("586e3ac78426af7af1425690"), "num_atoms" : 63, "idxd" : 34}
{ "_id" : ObjectId("586e3ac48426af7af1425651"), "num_atoms" : 62, "idxd" : 1 }
{ "_id" : ObjectId("586e3ac88426af7af1425697"), "num_atoms" : 61, "idxd" : 96}
{ "_id" : ObjectId("586e3ac88426af7af14256a9"), "num_atoms" : 61, "idxd" : 97}
{ "_id" : ObjectId("586e3ac78426af7af1425685"), "num_atoms" : 60, "idxd" : 90}
{ "_id" : ObjectId("586e3ac78426af7af142568a"), "num_atoms" : 60, "idxd" : 61}
{ "_id" : ObjectId("586e3ac88426af7af14256a2"), "num_atoms" : 59, "idxd" : 66}
{ "_id" : ObjectId("586e3ac78426af7af142566e"), "num_atoms" : 58, "idxd" : 93}
{ "_id" : ObjectId("586e3ac78426af7af1425677"), "num_atoms" : 58, "idxd" : 62}
{ "_id" : ObjectId("586e3ac78426af7af1425683"), "num_atoms" : 58, "idxd" : 94}
{ "_id" : ObjectId("586e3ac78426af7af142568f"), "num_atoms" : 58, "idxd" : 30}
{ "_id" : ObjectId("586e3ac88426af7af14256aa"), "num_atoms" : 58, "idxd" : 63}
{ "_id" : ObjectId("586e3ac48426af7af1425652"), "num_atoms" : 57, "idxd" : 2 }
{ "_id" : ObjectId("586e3ac88426af7af14256ac"), "num_atoms" : 57, "idxd" : 85}
{ "_id" : ObjectId("586e3ac78426af7af1425676"), "num_atoms" : 56, "idxd" : 69}
{ "_id" : ObjectId("586e3ac78426af7af142567a"), "num_atoms" : 56, "idxd" : 58}
{ "_id" : ObjectId("586e3ac78426af7af142568e"), "num_atoms" : 56, "idxd" : 91}

and then I want to update "idxd" with a serial number ( insert a new serial number "idxd2" is also OK), I tried:

var count=1;
db2.zinc_data.find().forEach(function(mydoc){ 
    db2.zinc_data.update({"idxd":{$gt:0}},{$set:{"idxd":count}});
    count++;
    print(count);
})

But it does not work. This collection have 20000000 line data, So i can not "find idxd and update idxd", I just want to get a serial number after sort operation.

Any help here, or if someone can point me to some good documentation or tutorials - either way would be very helpful!'

Thanks!

Answer 1

You can insert serial number in the first step.

var counter = 0;
db.zinc_data.find().sort({"num_atoms":-1}).forEach(function(mydoc){ 
    db2 = connect("database:port/zinc_Purtest_sort");
    mydoc.idxd = ++counter;
    db2.zinc_data.insert(mydoc);
})

Output:

> db.<sorted_data_table>.find({}, {_id : 0})
{ "num_atoms" : 76, "idxd" : 1 }
{ "num_atoms" : 74, "idxd" : 2 }
{ "num_atoms" : 66, "idxd" : 3 }
{ "num_atoms" : 63, "idxd" : 4 }
{ "num_atoms" : 62, "idxd" : 5 }
{ "num_atoms" : 61, "idxd" : 6 }
{ "num_atoms" : 61, "idxd" : 7 }
{ "num_atoms" : 60, "idxd" : 8 }
{ "num_atoms" : 60, "idxd" : 9 }
{ "num_atoms" : 59, "idxd" : 10 }
{ "num_atoms" : 58, "idxd" : 11 }
{ "num_atoms" : 58, "idxd" : 12 }
{ "num_atoms" : 58, "idxd" : 13 }
{ "num_atoms" : 58, "idxd" : 14 }
{ "num_atoms" : 58, "idxd" : 15 }
{ "num_atoms" : 57, "idxd" : 16 }
{ "num_atoms" : 57, "idxd" : 17 }
{ "num_atoms" : 56, "idxd" : 18 }
{ "num_atoms" : 56, "idxd" : 19 }
{ "num_atoms" : 56, "idxd" : 20 }