Modify the primary key type of MongoDB, record

Because the preliminary design is not week-long, the primary key _ id is objectid, so it is not convenient to update and maintain. It is too troublesome to modify it later.

// A duplicate record will be created. "city" and "category" are the unique indexes in the collection.
DB. categorycount. Find ({"_ id": {"$ type": 7}). foreach (function (x ){

X. _ id = "" + X. City + X. category;
DB. categorycount. Save (X );
});

// Through the above call, you have copied a record. The primary key is not of the string type. The record whose old objectid is the primary key will be deleted below
DB. categorycount. Remove ({"_ id": {"$ type": 7 }});

// The type value corresponding to the type is

Type	Value
Double	1
String	2
Object	3
Array	4
Binary data	5
Object ID	7
Boolean	8
Date	9
Null	10
Regular Expression	11
JavaScript code	13
Symbol	14
JavaScript code with scope	15
32-bit integer	16
Timestamp	17
64-bit integer	18
Min key	255 *
Max key	127