Custom _id

• 你schema 有 _id mongo 就唔同你gen, 亦唔可以用 Schema.ObjectId 做ref, 會認唔到type 的

• 可以令 _id 有意思,

  • e.g. studentSchema, use regno as custom _id
  • e.g. teacherSchema, use teacherInitial as custom _id

• use uuid if you need to have id before add new stuff

  • e.g. attachmentSchema, need the id to rename the attachment before saving to database.

Schema.ObjectId

• if no need to use custom _id then use Schema.ObjectId

[{type: string}] vs [String]

In mongoose schema, latter is better as it treat it purely a string array, the former one will create _id for each element.

autoIndex & versionKey

// disable `autoindex` if you know you will not query this schema.
SubjectSchema.set('autoIndex', false);

// disable `versionKey` if you know you don't need to monitor the update.
SubjectSchema.set('versionKey', false);

Use variable as a number

var Teacher = 1;
var Counselor = 2;
var HeadCounselor = 3
var Classmaster = 4
var Headmaster = 5
var Previleged = 6
// ...
role: { type: Int, min: Teacher, max: Previleged}