a quick question regarding how to define a compound index
as per the definition I can create a compound index as below and it would create a compound index for student_id and class_id.
db.students.createIndex({"student_id":1,"class_id":1});
however what will happen if I give something like this
db.students.createIndex({"student_id,class_id":1})
the syntax is valid and it accepts the index, but I am not sure how the index would be created.
any thoughts ?
Well if you do that and then just run db.students.getIndexes() you will see that the index is created for a field called student_id,class_id - which is exactly what you asked for, i.e. not a compound index but an index on a field with a comma in its name.
{
"v" : 1,
"key" : {
"student_id,class_id" : 1.0
},
"name" : "student_id,class_id_1",
"ns" : "tmp.students"
}