Aggregation Pipeline Builder

Limitations

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

Create an Aggregation Pipeline

1

Add an aggregation pipeline stage.

In the aggregation pipeline pane in the lower-left corner, click the Select... dropdown and select the aggregation pipeline stage to use for the first stage of the pipeline:

2

Fill in the pipeline stage.

Fill in your selected stage. If you enable Auto Preview, preview documents update automatically to the right of the stage to reflect the results of your pipeline as it progresses. You can adjust the width of the pipeline stage by dragging its border to the right.

3

Add additional pipeline stages.

Click Add Stage to add additional aggregation stages below your last aggregation stage. Repeat steps 1 and 2 for each additional stage.

Note

The toggle to the right of the name of each pipeline stage dictates whether that stage is included in the pipeline. Toggling a pipeline stage also updates the pipeline preview, which reflects whether or not that stage is included.

Example

The following pipeline excludes the first $match stage and only includes the $project stage:

4

Run the pipeline.

Click Run at the top right of the pipeline builder. Compass returns your results in the document view.

Warning

When you click Run, the aggregation runs against the entire collection.

5

Edit the pipeline.

Click Edit at the top of your pipeline toolbar to return to the aggregation pipeline builder. You can make changes to your pipeline from there.

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 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.

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: