How to remove a field in MongoDB from the command line?

Question

MongoDB

Hello, the task ahead is:
There are 800 fields with marks

> db.grades.find().count()
800
> db.grades.find()
{ "_id" : ObjectId("50906d7fa3c412bb040eb57a"), "student_id" : 0, "type" : "homework", "score" : 63.98402553675503 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb579"), "student_id" : 0, "type" : "homework", "score" : 14.8504576811645 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb578"), "student_id" : 0, "type" : "quiz", "score" : 31.95004496742112 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb577"), "student_id" : 0, "type" : "exam", "score" : 54.6535436362647 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57b"), "student_id" : 1, "type" : "exam", "score" : 74.20010837299897 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57c"), "student_id" : 1, "type" : "quiz", "score" : 96.76851542258362 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57e"), "student_id" : 1, "type" : "homework", "score" : 44.31667452616328 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57d"), "student_id" : 1, "type" : "homework", "score" : 21.33260810416115 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57f"), "student_id" : 2, "type" : "exam", "score" : 19.88180838833524 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb582"), "student_id" : 2, "type" : "homework", "score" : 97.75889721343528 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb581"), "student_id" : 2, "type" : "homework", "score" : 60.9750047106029 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb584"), "student_id" : 3, "type" : "quiz", "score" : 82.59760859306996 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb583"), "student_id" : 3, "type" : "exam", "score" : 92.6244233936537 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb585"), "student_id" : 3, "type" : "homework", "score" : 50.81577033538815 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb586"), "student_id" : 3, "type" : "homework", "score" : 92.71871597581605 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb580"), "student_id" : 2, "type" : "quiz", "score" : 1.528220212203968 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb58a"), "student_id" : 4, "type" : "homework", "score" : 28.656451042441 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb58b"), "student_id" : 5, "type" : "exam", "score" : 49.41260067227861 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb587"), "student_id" : 4, "type" : "exam", "score" : 87.89071881934647 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb588"), "student_id" : 4, "type" : "quiz", "score" : 27.29006335059361 }
Type "it" for more

Of these, 400 fields contain data on grades with homework

> db.grades.find({type:'homework'}).count()
400

It is necessary to select all fields with homework and sort them by students_id and score

> db.grades.aggregate([{'$match':{type:'homework'}}, {'$group':{'_id':'$student_id', 'score':{$min:'$score'}}}, {'$sort':{_id:1}}])
{ "_id" : 0, "score" : 14.8504576811645 }
{ "_id" : 1, "score" : 21.33260810416115 }
{ "_id" : 2, "score" : 60.9750047106029 }
{ "_id" : 3, "score" : 50.81577033538815 }
{ "_id" : 4, "score" : 5.244452510818443 }
{ "_id" : 5, "score" : 23.29430953857654 }
{ "_id" : 6, "score" : 81.23822046161325 }
{ "_id" : 7, "score" : 63.35102050393443 }
{ "_id" : 8, "score" : 66.42784200049636 }
{ "_id" : 9, "score" : 16.60130789148128 }
{ "_id" : 10, "score" : 6.094174990746648 }
{ "_id" : 11, "score" : 27.42742674795513 }
{ "_id" : 12, "score" : 51.69676516705788 }
{ "_id" : 13, "score" : 0.4838914493376478 }
{ "_id" : 14, "score" : 63.69676709320795 }
{ "_id" : 15, "score" : 7.475648374118382 }
{ "_id" : 16, "score" : 12.8489522283682 }
{ "_id" : 17, "score" : 32.33461505658801 }
{ "_id" : 18, "score" : 16.31570053358192 }
{ "_id" : 19, "score" : 19.50958720409689 }
Type "it" for more

Then you need to completely erase the fields with records of minimum homework grades for each student.
That is, in the end, we should get the result of such a plan:

> db.grades.find()
{ "_id" : ObjectId("50906d7fa3c412bb040eb57a"), "student_id" : 0, "type" : "homework", "score" : 63.98402553675503 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb578"), "student_id" : 0, "type" : "quiz", "score" : 31.95004496742112 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb577"), "student_id" : 0, "type" : "exam", "score" : 54.6535436362647 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57b"), "student_id" : 1, "type" : "exam", "score" : 74.20010837299897 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57c"), "student_id" : 1, "type" : "quiz", "score" : 96.76851542258362 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57e"), "student_id" : 1, "type" : "homework", "score" : 44.31667452616328 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb57f"), "student_id" : 2, "type" : "exam", "score" : 19.88180838833524 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb582"), "student_id" : 2, "type" : "homework", "score" : 97.75889721343528 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb584"), "student_id" : 3, "type" : "quiz", "score" : 82.59760859306996 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb583"), "student_id" : 3, "type" : "exam", "score" : 92.6244233936537 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb586"), "student_id" : 3, "type" : "homework", "score" : 92.71871597581605 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb580"), "student_id" : 2, "type" : "quiz", "score" : 1.528220212203968 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb58b"), "student_id" : 5, "type" : "exam", "score" : 49.41260067227861 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb587"), "student_id" : 4, "type" : "exam", "score" : 87.89071881934647 }
{ "_id" : ObjectId("50906d7fa3c412bb040eb588"), "student_id" : 4, "type" : "quiz", "score" : 27.29006335059361 }
Type "it" for more

Can you please tell me how to delete the line with the minimum mark on the remote sensing ... Or did I make the request wrong (even though it displays the correct values ​​on the screen), that I can’t shove it into .deleteMany() , .updateMany()?

Answer 1

Read https://docs.mongodb.com/v3.2/reference/method/db....
Read about $unset
Read about multi: true

Answer 2

> db.grades.update({{'$match':{type:'homework'}}, {'$group':{'_id':'$student_id', 'score':{$min:'$score'}}}}, {$unset: {score:1}}, {multi: true})
2016-10-26T12:52:04.706+0300 E QUERY    [thread1] SyntaxError: invalid property id @(shell):1:18

What am I doing wrong?