Mongoose sequence plugin
This plugin lets you create fields which autoincrement their value:
- every time a new document is inserted in a collection
- when you explicitly 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 counters can be set for a collection.
From version 3 to version 4
Version 3 is now deprecated. In order to migrate to the new version the only change you need to do is to pass
mongoose to the required module as explained in the requiring section.
From version 4 to version 5
An important fix about scoped counters is not backward compatible. You cannot use version 5 with scoped counters already present on your DB.
This plugin needs mongoose version 4.0.0 or above.
npm install --save mongoose-sequence
const mongoose =const AutoIncrement = mongoose;
Note You must pass your mongoose instance to the plugin for it to work.
Let's say you want to have an
id field in your
user collection which has a unique auto-incremented value.
The user schema is something like this:
UserSchema = mongoose;mongoose;
You don't need to define the
id field in your schema because the plugin automatically sets it for you. The only thing you have to do is to call:
after requiring the plugin.
Every time a new user is created, the
id field will have an incremented 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
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 interfere:
UserSchema = mongoose;UserSchema;
In this case you don't have to specify
inc_field because the default value is
Not automatic sequences
Let say our user model has a
rank field which gives 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 every time an event occurs. Because we have concurrent access to our database we want to be sure that the increment of this counter happens safely.
Let's start by modifying our schema:
UserSchema = mongoose;
This time we specified explicitly the field
rank. There is no difference between defining and omitting the field specification. The only constraint 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:
disable_hooks. This avoids the field being 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's an example:
You noticed that the method
setNext takes, as argument, the counter field name. It 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:
and then use:
So, if you do 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 is 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 to, so two counters for two different schemas can collide.
So use a unique id to be sure to avoid collision. In the case of a collision the plugin will raise an error.
As we will see, the use of an id for the counter is mandatory when you're defining a
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 by
city and we want to save the
inhabitant_number according to these two pieces of information.
The schema is like this:
UserSchema = mongoose;
Every time a new Parisian is added the count of Parisians has to be incremented. The inhabitants of New York must not interfere and have their separate counting. We should define a scoped counter which increments the counter depending on the value of other fields.
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 =name: 'Patrice'country: 'France'city: 'Paris';user;
This user will have the
inhabitant_number counter set to 1.
If now we add a new inhabitant from New York, this will have its counter set to 1 also, because the counter is referred to by the value of the fields
If we want to increment this counter manually we have to specify the id of the sequence in the
Of course this example is a bit forced and this is for sure not the perfect use case. The fields
city have to be present and must not change during the life of the document because no automatic hooks are set on the change of those values. But there are situations when you want a similar behavior.
Reset a counter
It's possible to programmatically reset a counter through the Model's static method
counterReset(id, reference, callback). The method takes these parameters:
- id: the counter to reset. It's mandatory
- reference: Lets you reset only a specific reference of the counter, if the counter has referenced fields. Optional. By default it resets all the counters for the
- callback: A callback which receives an error in case of any. Mandatory
This plugin accepts a series of options.
- inc_field: The name of the field to increment. Mandatory, default is
- 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
- collection_name: By default the collection name to mantain the status of the counters is
counters. You can override it using this option
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)