node-red-nodes/storage/mongodb/README.md

node-red-node-mongodb
=====================

A <a href="http://nodered.org" target="_new">Node-RED</a> node to save data in a MongoDB database.

**Note** : This is the same node as is/was in the core of Node-RED. If you already
have it installed you do NOT need this node.

Pre-requisite
-------------

To run this you need a local MongoDB server running. For details see
<a href="https://www.mongodb.org/" target="_new">the MongoDB site</a>.

Install
-------

Run the following command in the root directory of your Node-RED install.
Usually this is `~/.node-red` .

        npm install node-red-node-mongodb

Usage
-----

Nodes to save and retrieve data in a local MongoDB instance.

###Input

Calls a MongoDB collection method based on the selected operator.

*Find* queries a collection using the **msg.payload** as the query statement as
per the *.find()* function.

Optionally, you may also (via a function) set

- a **msg.projection** object to constrain the returned fields,
- a **msg.sort** object,
- a **msg.limit** number,
- a **msg.skip** number.

*Count* returns a count of the number of documents in a collection or matching a
query using the **msg.payload** as the query statement.

*Aggregate* provides access to the aggregation pipeline using the **msg.payload** as the pipeline array.

You can either set the collection method in the node config or on **msg.collection**.
Setting it in the node will override **msg.collection**.

See the <a href="http://docs.mongodb.org/manual/reference/method/db.collection.find/" target="new">*MongoDB collection methods docs*</a> for examples.

The result is returned in **msg.payload**.

###Output

A simple MongoDB output node. Can save, insert, update and remove objects from a chosen collection.

MongoDB only accepts objects.

Save and insert can either store **msg** or **msg.payload**. If msg.payload is
selected it should contain an object. If not it will be wrapped in an object with a name of payload.

*Save* will update an existing object or insert a new object if one does not already exist.

*Insert* will insert a new object.

*Update* will modify an existing object or objects. The query to select objects
to update uses **msg.query** and the update to the element uses **msg.payload**.
Update can add a object if it does not exist or update multiple objects.

*Remove* will remove objects that match the query passed in on **msg.payload**.
A blank query will delete *all of the objects* in the collection.

You can either set the collection method in the node config or on **msg.collection**.
Setting it in the node will override **msg.collection**.

By default MongoDB creates an **msg._id** property as the primary key - so
repeated injections of the same **msg** will result in many database entries.
If this is NOT the desired behaviour - ie. you want repeated entries to overwrite,
then you must set the **msg._id** property to be a constant by the use of a previous function node.
This must be done at the correct level. If only writing msg.payload then payload must contain the \_id property.
If writing the whole msg object then it must contain an \_id property.

This could be a unique constant or you could create one based on some other msg property.

Currently we do not limit or cap the collection size at all...