Guides / Managing results / Refine results / Sorting results

By design, Algolia provides one ranking formula per index: when you want to provide different rankings for the same data you need to use different indices for each ranking. These additional indices are called replicas.

If you want to set up sort by attribute it is important that you understand replica indices.

To sort by attribute, you will first need to create a replica index and then modify the ranking formula of the replica. This can be done through the Dashboard and the API.

This guide will help you set up the necessary back end for sorting by attribute, but you need to configure your front end (with widgets or custom logic) to make the option accessible to your users.

Attribute format

Attributes used for sorting must have boolean or numerical values. You cannot use a string attribute and dates must be represented as numbers.

Numerical values should be indexed as actual numbers, not strings.

Using the API

Creating a replica

To create replicas, use the setSettings method on your primary index. You can add more than one replica at a time if you want to provide multiple alternative sorting strategies.

Algolia offers two flavors of replicas, standard and virtual replicas. You can choose either one depending on your needs.

The example below shows how to create the products_price_desc standard replica.

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$index->setSettings([
  'replicas' => [
    'products_price_desc'
  ]
]);

The example below shows how to create the products_price_desc virtual replica.

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$index->setSettings([
  'replicas' => [
    'virtual(products_price_desc)'
  ]
]);

Changing replica settings

To change a replica’s settings:

  1. Initialize the replica.
  2. Use setSettings to change the replica’s setting.

In the example below, the products_price_desc standard replica is sorted by price, descending.

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$replica_index = $client->initIndex('products_price_desc');

$replica_index->setSettings([
  'ranking' => [
    'desc(price)',
    'typo',
    'geo',
    'words',
    'filters',
    'proximity',
    'attribute',
    'exact',
    'custom'
  ]
]);

In the example below, the products_price_desc virtual replica is sorted by price, descending. Remember, a virtual replica reuses its primary index’s ranking and settings. That’s why only the attributes used for sorting are specified here.

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$replica_index = $client->initIndex('products_price_desc');

$replica_index->setSettings([
  'customRanking' => [
    'desc(price)'
  ]
]);

Using the dashboard

Creating a replica

  1. Go to the Indices section of the dashboard and select your index.
  2. Click the Replicas tab.
  3. Click the Create Replica Index button. If you are on a Premium plan, choose between a standard or virtual replica depending on your needs.
  4. Repeat for each replica you want to add.
  5. Don’t forget to save your changes.

Changing replica settings

  1. Go to the Indices section of the dashboard and select your replica index.
  2. Click the Configuration tab.
  3. In the Ranking and Sorting section, use the + Add sort-by attribute button to add the attribute you want to sort by. Then select either Ascending or Descending to the right of the attribute name.
  4. Don’t forget to save your changes.

When using replicas for sorting, you should set the typoTolerance parameter to min. This ensures the most relevant results show up and get sorted.

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