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A Segment is a subset of a Collection: it’s a saved filter of your Collection. Segments are designed for those who want to systematically visualize data according to specific sets of filters. It allows you to save filter configurations so users don’t have to do repetitive actions every day.

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From your back-end

Sometimes, Segment filters are complicated and closely tied to your business. Forest allows you to code how the Segment is computed. For instance, you might implement a Segment on the products collection to allow admin users to see the bestsellers at a glance.

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Example

In the following example, we are making queries using the Forest Query Interface.As Forest does not impose any restriction on the handler, you are free to call external APIs or query your database directly instead.
The only requirement when implementing a Segment from your back-end is to return a valid ConditionTree. 
agent.customizeCollection('products', collection =>
  collection.addSegment('mostPurchased', async context => {
    // Query the ids of the 10 most ordered products.
    const rows = await context.dataSource
      .getCollection('orders')
      .aggregate({}, { operation: 'Count', groups: [{ field: 'product_id' }] }, 10);

    // Return a condition tree which matches those records
    return { field: 'id', operator: 'In', value: rows.map(r => r['product_id']) };
  });
);