This plugin let you create fields which autoincrement their value:
- every time a new document is inserted in a collection
or - when you esplicitly want to increment them
This increment can be:
- global: every document has a unique value for the sequence field
- scoped: the counter depends on the value of other field(s)
Multiple counter can be set for a collection.
This plugin need mongoose version 4.0.0 or above
npm install --save mongoose-sequence
Let's say you want to have an id
field in your user
collection which has an unique auto-incremented value.
The user schema is something like this:
UserSchema = mongoose.Schema({
name: String
});
mongoose.model('User', UserSchema);
You don't need to define the id
field in your schema because the plugin automatically set it for you. The only thing you have to do is to call:
UserSchema.plugin(AutoIncrement, {inc_field: 'id'});
After requiring the plugin
var AutoIncrement = require('mongoose-sequence');
Every time a new user is created, the id
field will have an incremental number. The operation is atomic and is based on this specification.
A commodity collection named counters
is created for you. You can override the name of this collection but we will see this later with the options
.
If you want to increment the _id
field which is special to mongoose, you have to explicitly specify it as a Number and tell mongoose to not interfer:
UserSchema = mongoose.Schema({
_id: Number,
name: String
}, { _id: false });
UserSchema.plugin(AutoIncrement);
In this case you don't have to specify inc_field
because the default value is _id
Let say our user model has a rank
field which cgives the rank of the user in a tournament. So it saves the arrival order of a user to the end of our amazing game. This field is of course a sequence but has to be incremented everytime an event occours. Because we have concurrent access to database we want to be sure that the increment of this counter happens safely.
Let's start modify our schema
UserSchema = mongoose.Schema({
name: String,
rank: Number
});
this time we specified explicitly the field rank
. There is no difference between defining and omitting the field specification. The only constraints is that the field has to be of type Number
, otherwise the plugin will raise an error.
So, let's say to the plugin we want the rank
field to be a safe counter
UserSchema.plugin(AutoIncrement, {inc_field: 'rank', disable_hooks: true});
We specified disable_hooks
. This avoid the field to be incremented when a new document is saved. So, how to increment this field? Your models have a new method: setNext. You must specify which sequence you want to increment and a callback. Here an example:
User.findOne({name:'George'}, function(err, user){
user.setNext('rank', function(err, user){
if(err) console.log('Cannot increment the rank because',err);
});
});
You noticed that the method setNext
takes, as argument, the counter field name. Is possible to give a name to the counter and use it as reference. For the previous example we can define the counter like this:
UserSchema.plugin(AutoIncrement, {id:'rank_counter', inc_field: 'rank', disable_hooks: true});
and then using
user.setNext('rank_counter', function(err, user){
...
});
So, if you not specify the id
, the field name is used. Even if you're not forced to specify an id, its use is strongly suggested. This because if you have two different counters, which refers to fields with the same name, they will collide and incrementing one, will increment the other too. Counters are not bound to the schema they refer too, so two counters for two different schemas can collide.
So use unique id to be sure to avoid collision. In case of collision the plugin will raise an error.
As we will see, the use of an id for the counter is mandatory when you're are defining a scoped counter
.
NOTE: When you call setNext
the document is automatically saved. This behavior has changed since version 3.0.0. If you use a prior version you have to call save by yourself.
Let say our users are organized for country
and city
. And we want to save the inhabitant_number
according to the two informations.
The schema is like this:
UserSchema = mongoose.Schema({
name: String,
country: String,
city: String,
inhabitant_number: Number
});
Every time a new Parisian is added the counting of Parisians have to be incremented. The inhabitants of New York must not interfer and have their separated counting. We should define a scoped counter which increment the counter depending on the value of other fields.
UserSchema.plugin(AutoIncrement, {id: 'inhabitant_seq', inc_field: 'inhabitant_number', reference_fields: ['country','city'] });
Notice that we have to use an id for our sequence, otherwise the plugin will raise an error. Now save a new user
var user = new User({
name: 'Patrice',
country: 'France',
city: 'Paris'
});
user.save();
This user will have the inhabitant_number
counter to 1.
If now we add a new inhabitant from New York, this will have the counter to 1 also, because the counter is referred to the value of the fields country
and city
.
If we want to increment manually this counter we have to specify the id of the sequence in the setNext
method
user.setNext('inhabitant_seq', function(err, user){
user.inhabitant_number; // the counter value
});
Of course this example is a bit forced and this is for sure not the perfect use case. The field country and city have to be present and must not change during the life of the document because no automatic hook are set on the change of those values. But there are situations when you want a similar behavior.
It's possible to programmatically reset a counter through the Model static method counterReset(id, reference, callback)
. The method take those parameters:
- id: the counter to reset. It's mandatory
- reference: Let you reset only a specific reference of the counter, if the counter has referenced fields. Optional. By default it reset all the counters for the
id
- callback: A callback which receive an error in case of any. Mandatory
Some examples
Model.counterReset('counter_id', function(err) {
// Now the counter is 0
});
Model.counterReset('inhabitants_id', function(err) {
// If this is a referenced fields, now all the counter are 0
});
Model.counterReset('inhabitants_id',{country: 'France', city: 'Paris'}, function(err) {
// If this is a referenced fields, only the counter for Paris/France is 0
});
This plugin accept a series of options.
- inc_field: The name of the field to increment. Mandatory, default is
_id
- id: Id of the sequence. Is mandatory only for scoped sequences but its use is strongly encouraged.
- reference_fields: The field to reference for a scoped counter. Optional
- disable_hooks: If true, the counter will not be incremented on saving a new document. Default to
false
- collection_name: By default the collection name to mantain the status of the counters is
counters
. You can override it using this option
When using insertMany
the plugin won't increment the counter because the needed hooks are not called. If you need to create several documents at once, use create
instead and pass an array of documents (refer to #7)