Mongoose经常返回e11000 error的原因分析

var CatalogSchema = new Schema({
 idCat: {
 type: String,
 default: '',
 trim: true,
 unique: 'Id should be unique!',
 required: 'Id cannot be blank'
 },
 titleCat: {
 type: String,
 default: '',
 trim: true,
 unique: 'Title should be unique!',
 required: 'Title cannot be blank'
 }
 });

mongoose.model('Catalog', CatalogSchema);

> db.catalogs.getIndexes()
[
 {
 "v" : 1,
 "key" : {
  "_id" : 1
 },
 "name" : "_id_",
 "ns" : "ocr-dev.catalogs"
 },
 {
 "v" : 1,
 "unique" : true,
 "key" : {
  "name" : 1
 },
 "name" : "name_1",
 "ns" : "ocr-dev.catalogs",
 "background" : true
 },
 {
 "v" : 1,
 "unique" : true,
 "key" : {
  "title" : 1
 },
 "name" : "title_1",
 "ns" : "ocr-dev.catalogs",
 "background" : true
 },
 {
 "v" : 1,
 "unique" : true,
 "key" : {
  "idCat" : 1
 },
 "name" : "idCat_1",
 "ns" : "ocr-dev.catalogs",
 "background" : true
 },
 {
 "v" : 1,
 "unique" : true,
 "key" : {
  "titleCat" : 1
 },
 "name" : "titleCat_1",
 "ns" : "ocr-dev.catalogs",
 "background" : true
 }
]

> db.catalogs.drop()
false
> db.catalogs.getIndexes()
[ ]