Aggregation Pipeline Builder

Tasks

You can use the Compass Aggregation Pipeline Builder to:

• Create a new aggregation pipeline

• Save a pipeline

• Open a saved pipeline

• Set maxTimeMS for Aggregation Queries

• Set the documents limit or auto preview documents

• View or change pipeline settings

• View the explain plan for pipelines

• Export Aggregation Results

• Specify custom collation

• Create a view from pipeline results

• Import a pipeline from plain text

• Export a pipeline to Java, Node, C#, and Python 3

• Refresh Document Counts

Limitations

• The $out stage is not available if you are connected to a Data Lake.

• You cannot run the Atlas Search $search or $searchMeta stages on a time series collection.

Create an Aggregation Pipeline

MongoDB Compass provides different modes to create aggregation pipelines:

• Stage View Mode, a visual pipeline editor that preloads pipeline syntax based on your selected stages.

• Focus Mode, a feature of Stage View Mode where you edit one pipeline stage at a time. Focus Mode helps you manage complex or deeply nested aggregation pipeline stages.

• Text View Mode, a text-based pipeline editor that accepts raw pipeline syntax.

To see how to create an aggregation pipeline, select the tab corresponding to your chosen view mode:

Save a Pipeline

You can save a pipeline so that you can find it later. If you load a saved pipeline, you can change it without changing the original saved copy. You can also create a view from your pipeline results.

To save your pipeline:

1

Click the save dropdown button

Click the Save dropdown button at the top of the pipeline builder. Click on Save pipeline as...

2

Enter a name for your pipeline

3

Click Save

Open a Saved Pipeline

1. Click the Folder icon at the top left of the pipeline builder.

   

2. Hover over the pipeline you want to open and click Open.

   

3. In the modal, click Open Pipeline.

Set maxTimeMS for Aggregation Queries

Use the maxTimeMS parameter on the Aggregations tab to specify an upper time limit in milliseconds on the aggregation pipelines that run in Compass.

To enable maxTimeMS for aggregation operations:

1

On the Aggregations tab, click More Options.

2

Enter a value next to Max Time MS to set a maximum amount of time in milliseconds that an aggregation pipeline can run. For a 5 second limit, enter 5000.

If your aggregation operation goes over the time limit, Compass raises the following error:

Set the Documents Limit or Auto Preview Documents

Use the toggles at the top of the pipeline builder to set the limit on the number of sampled documents or to enable auto preview.

View or Change Pipeline Settings

To view and change pipeline settings:

1. Click the gear icon at the upper right of the pipeline builder to open the Settings panel.

2. Change any of the following pipeline settings.

   Option	Description	Default
   Comment Mode	When enabled, adds helper comments to each stage.	Enabled
   Number of Preview Documents	Number of documents to show in the preview.	20
   Limit	When Sample Mode is enabled, specifies the number of documents passed to $group, $bucket, and $bucketAuto stages. Lower limits improve pipeline running time, but may miss documents.	100000

3. Click Apply to save changes and close the Settings panel.

Explain Plan for Pipelines

Use the Explain button to view the explain plan that helps you understand the performance of your pipelines. You can view the explain plan at any point while creating or editing your pipeline.

To view your pipeline explain plan, click Explain in the right corner of your pipeline toolbar.

Your results are presented in this format:

Specify Custom Collation

Use custom collation to specify language-specific rules for string comparison, such as rules for letter case and accent marks.

To specify a custom collation:

1. Click More Options in the top right corner of the pipeline builder.

   

2. Enter your collation document.

Export Aggregation Results

To export results from your aggregation pipeline:

1. Connect to the deployment containing the collection you wish to export data from.

   To learn how to connect to a deployment, see Connect to MongoDB.

2. Navigate to your target collection.

   You can either select the collection from the Collections tab or click the collection in the left-hand pane.

3. Create an aggregation pipeline and run for results.

   To learn how to create an aggregation pipeline, see Create an Aggregation Pipeline.

4. Click Export.

5. Choose the appropriate file type.

   Under Select Export File Type, select either JSON or CSV. If you select JSON, your data is exported to the target file as an array of JSON objects.

6. Under Output, choose where to export the file to.

   

7. Click Export.

Create a View from Pipeline Results

To create a view from your pipeline results:

1. Click the arrow next to the Save button at the top of the pipeline builder.

2. Click Create a View.

3. Enter a name for your view.

4. Click Create.

Compass creates a view from your pipeline results in the same database where the pipeline was created.

Refresh Document Counts

When you delete or add a document, the count results value on the Aggregations tab does not automatically update to reflect the new document count.

To update the count results:

1

(Optional) If the results have not been counted, click the count results link.

2

Click the refresh button.

Compass updates the count results and displays the updated number of documents in the collection.

Example

In this example, you create and run a pipeline for a collection with airline data. You can download this dataset from the following link: air_airlines.json.

For instructions on importing JSON data into your cluster, see Import Data into a Collection. This example assumes you have the data in the example.air_airlines namespace.

Procedure

1. Connect to a database deployment. For information on how to connect to a database deployment, see Connect via Compass.

2. Select the example database where the air_airlines collection exists.

3. Create the Pipeline

   
   

   The following pipeline has two aggregation stages: $group and $match.

   • The $group stage groups documents by their active status and country. The stage also adds a new flightCount field containing the number of documents in each group.

   • The $match stage filters documents to return documents with a flightCount value greater than or equal to 5.

     

4. Run the Pipeline.

   Click Run at the top right of the pipeline builder.

The pipeline returns documents, as shown in the following abbreviated example: