> ## Documentation Index
> Fetch the complete documentation index at: https://docs.datris.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# MongoDB Destination

> Send data to MongoDB

The MongoDB destination writes JSON documents to a MongoDB collection. It supports upserts, transactions, and two JSON input modes.

## Schema Requirement

The source schema must contain a single field named `_json` of type `string`. Each value in this field is a JSON document that will be written to the target collection.

## JSON Modes

The JSON input mode is controlled by `everyRowContainsObject` in the source `fileAttributes.jsonAttributes`:

| Value   | Description                                                                          |
| ------- | ------------------------------------------------------------------------------------ |
| `true`  | Each line of the file is a separate JSON document (newline-delimited JSON). Default. |
| `false` | The file contains a single JSON array; each element becomes a separate document.     |

## Upsert with Compound Keys

Specify one or more fields in `keyFields` to perform an upsert instead of a plain insert. The pipeline matches existing documents by the compound key formed from these fields. If a matching document exists it is replaced; otherwise a new document is inserted.

## Truncate Before Write

Set `truncateBeforeWrite` to `true` to delete all documents from the target collection before writing. This effectively replaces the entire collection on each run.

## Transaction Support

By default (`useTransaction: true`), all write operations execute inside a MongoDB transaction. If any error occurs during the write, the transaction is aborted and no partial data is persisted. Set `useTransaction: false` to disable transactional writes.

## Configuration Example

```json theme={null}
{
  "name": "events_mongodb",
  "source": { "..." : "..." },
  "destination": {
    "database": {
      "dbName": "analytics",
      "table": "events",
      "useMongoDB": true,
      "keyFields": ["event_id", "source"],
      "truncateBeforeWrite": false,
      "useTransaction": true
    }
  }
}
```

MongoDB connection credentials are configured globally in `application.yaml` via `secrets.mongoDbSecretName`. See [Configuration Reference](/configuration-reference) for Vault secret format.

### Field Reference

| Field                 | Required | Default | Description                                          |
| --------------------- | -------- | ------- | ---------------------------------------------------- |
| `dbName`              | yes      |         | Target database name                                 |
| `table`               | yes      |         | Target collection name                               |
| `useMongoDB`          | yes      | `false` | Must be `true` to enable MongoDB destination         |
| `keyFields`           | no       |         | Array of field names forming the compound upsert key |
| `truncateBeforeWrite` | no       | `false` | Delete all documents before writing                  |
| `useTransaction`      | no       | `true`  | Wrap all writes in a MongoDB transaction             |

## Completion Notification

A pipeline notification is published to ActiveMQ on completion. See [Notifications](/notifications) for details.