MongoDB is a NoSQL database that stores JSON-like documents. These documents are stored in collections, which are like database tables. The fields inside these document can differ from document to document, but generally they are all more or less the same. However documents with different schemas can be stored in the same collection.
##### ObjectIds
MongoDB uses the _id field as the id for a document. This has to be unique for every document in the collection. If no _id is provided when the document is created, a MongoDB [ObjectId](https://docs.mongodb.com/manual/reference/method/ObjectId/) is created for that document. This id includes a timestamp, a random element and an incrementing counter, to ensure it is unique even if multiple ids are created at the same time.
The _id is often represented as:
```js
{
_id:ObjectId("507f1f77bcf86cd799439011")
}
```
To be able to transmit these ids over JSON network connections, and to use them in Lowdefy apps, Lowdefy serializes these ids as (in YAML):
```yaml
_id:
_oid:507f1f77bcf86cd799439011
```
Ids specified in this way will be treated as ObjectIds by MongoDB requests and mutations.
The `MongoDBCollection` connection sets up a connection to a MongoDB deployment. A [connection URI](https://docs.mongodb.com/manual/reference/connection-string/index.html) with authentication credentials (username and password) is required. The URI can be in the standard or dns seedlist (srv) formats. Connections are defined on a collection level, since this allows for read/write access control on a per collection level. Access control can also be managed using the roles in the database.
- `databaseUri: string`:__Required__ - Connection uri string for the MongoDb deployment. Should be stored using the [_secret](operators/secret.md) operator.
- `databaseName: string`: Default:Database specified in connection string - The name of the database in the MongoDB deployment.
- `collection: string`:__Required__ - The name of the MongoDB collection.
- `read: boolean`: Default:`true` - Allow read operations like find on the collection.
- `write: boolean`: Default:`false` - Allow write operations like update on the collection.
The `MongoDBAggregation` request executes an [aggregation pipeline](https://docs.mongodb.com/manual/core/aggregation-pipeline/) in the collection specified in the connectionId. It returns the array of documents returned by the aggregation. Aggregation pipelines are MongoDB's data processing and aggregation framework. They are based on a series of stages, each of which apply a transformation to the data passed through them, like sorting, grouping or calculating additional fields.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#aggregate) for more information. Supported settings are:
- `bypassDocumentValidation: boolean`: Default:`false` - Allow driver to bypass schema validation in MongoDB 3.2 or higher.
- `collation: object`:Specify collation (MongoDB 3.4 or higher) settings for update operation.
- `comment: string`:Add a [comment](https://docs.mongodb.com/manual/reference/operator/query/comment/index.html) to the aggregation. These comments are visible in the MongoDB profile log, making them easier to interpret.
- `hint: string | object`:Add an index selection hint to an aggregation command.
The `MongoDBDeleteMany` request deletes multiple documents in the collection specified in the connectionId. It requires a filter, which is written in the query syntax, to select a documents to delete.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#updateOne) for more information. Supported settings are:
The `MongoDBDeleteOne` request deletes a single document in the collection specified in the connectionId. It requires a filter, which is written in the query syntax, to select a document to delete. It will delete the first document that matches the filter.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#updateOne) for more information. Supported settings are:
The `MongoDBFind` request executes a MongoDB [query](https://docs.mongodb.com/manual/tutorial/query-documents/) on the collection specified in the connectionId. It returns the array of documents returned by the query.
>Cursors are not supported. The request will return the whole body of the response as an array.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#find) for more information. Supported settings are:
- `projection: object`:The fields to return in the query. Object of fields to either include or exclude (one of, not both), `{'a':1, 'b': 1}` or `{'a': 0, 'b': 0}`.
- `hint: object`:Tell the query to use specific indexes in the query. Object of indexes to use, `{'_id':1}`.
- `comment: string`:Add a [comment](https://docs.mongodb.com/manual/reference/operator/query/comment/index.html) to the query. These comments are visible in the MongoDB profile log, making them easier to interpret.
The `MongoDBFindOne` request executes a MongoDB [query](https://docs.mongodb.com/manual/tutorial/query-documents/) on the collection specified in the connectionId. It returns the first document that matches the specified query.
>Cursors are not supported. The request will return the whole body of the response as an array.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#find) for more information. Supported settings are:
- `projection: object`:The fields to return in the query. Object of fields to either include or exclude (one of, not both), `{'a':1, 'b': 1}` or `{'a': 0, 'b': 0}`.
- `hint: object`:Tell the query to use specific indexes in the query. Object of indexes to use, `{'_id':1}`.
- `comment: string`:Add a [comment](https://docs.mongodb.com/manual/reference/operator/query/comment/index.html) to the query. These comments are visible in the MongoDB profile log, making them easier to interpret.
The `MongoDBInsertMany` request inserts an array of documents into the collection specified in the connectionId. If a `_id` field is not specified on a document, a MongoDB `ObjectID` will be generated.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#insertMany) for more information. Supported settings are:
The `MongoDBInsertOne` request inserts a document into the collection specified in the connectionId. If a `_id` field is not specified, a MongoDB `ObjectID` will be generated.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#insertOne) for more information. Supported settings are:
The `MongoDBUpdateMany` request updates multiple documents that match a certain criteria in the collection specified in the connectionId. It requires a filter, which is written in the query syntax, to select the documents to update.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#updateOne) for more information. Supported settings are:
- `arrayFilters: string[]`:Array filters for the [`$[<identifier>]`](https://docs.mongodb.com/manual/reference/operator/update/positional-filtered/) array update operator.
- `bypassDocumentValidation: boolean`: Default:`false` - Allow driver to bypass schema validation in MongoDB 3.2 or higher.
- `checkKeys: boolean`: Default:`false` - If true, will throw if bson documents start with $ or include a . in any key value.
- `collation: object`:Specify collation (MongoDB 3.4 or higher) settings for update operation.
The `MongoDBUpdateOne` request updates a single document in the collection specified in the connectionId. It requires a filter, which is written in the query syntax, to select a document to update. It will update the first document that matches the filter. If the `upsert` option is set to true, it will insert a new document if no document is found to update.
- `options: object`:Optional settings. See the [driver docs](https://mongodb.github.io/node-mongodb-native/3.3/api/Collection.html#updateOne) for more information. Supported settings are:
- `arrayFilters: string[]`:_Array_ - Array filters for the [`$[<identifier>]`](https://docs.mongodb.com/manual/reference/operator/update/positional-filtered/) array update operator.
