Add support of similar search

.code-samples.meilisearch.yaml

@@ -653,6 +653,8 @@ update_search_cutoff_1: |-
   client.index('movies').update_search_cutoff_ms(150)
 reset_search_cutoff_1: |-
   client.index('movies').reset_search_cutoff_ms
+get_similar_post_1: |-
+  client.index('INDEX_NAME').search_similar_documents('TARGET_DOCUMENT_ID')
 search_parameter_reference_ranking_score_threshold_1: |-
   client.index('INDEX_NAME').search('badman', {
     rankingScoreThreshold: 0.2

.rubocop_todo.yml

@@ -15,7 +15,7 @@ Metrics/BlockLength:
 # Offense count: 4
 # Configuration parameters: CountComments, CountAsOne.
 Metrics/ClassLength:
-  Max: 433
+  Max: 441
 
 # Offense count: 1
 # Configuration parameters: Max, CountKeywordArgs.

lib/meilisearch/index.rb

@@ -271,6 +271,14 @@ def search(query, options = {})
       response
     end
 
+    # document_id: Identifier of the target document
+    def search_similar_documents(document_id, **options)
+      options.merge!(id: document_id)
+      options = Utils.transform_attributes(options)
+
+      http_post("/indexes/#{@uid}/similar", options)
+    end
+
     ### FACET SEARCH
 
     def facet_search(name, query = '', **options)

spec/meilisearch/index/search/similar_spec.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+RSpec.describe 'MeiliSearch::Index - Search for similar documents' do
+  let(:new_index) { client.index('similar_test_search') }
+
+  before do
+    client.create_index('similar_test_search').await
+  end
+
+  it 'requires document_id parameter' do
+    expect { new_index.search_similar_documents }.to raise_error ArgumentError
+  end
+
+  it 'does a search for similar documents' do
+    enable_vector_store(true)
+
+    documents = [
+      {
+        title: 'Shazam!',
+        release_year: 2019,
+        id: '287947',
+        _vectors: { 'manual' => [0.8, 0.4, -0.5] }
+      },
+      {
+        title: 'Captain Marvel',
+        release_year: 2019,
+        id: '299537',
+        _vectors: { 'manual' => [0.6, 0.8, -0.2] }
+      },
+      {
+        title: 'How to Train Your Dragon: The Hidden World',
+        release_year: 2019,
+        id: '166428',
+        _vectors: { 'manual' => [0.7, 0.7, -0.4] }
+      }
+    ]
+
+    new_index.update_settings(
+      embedders: {
+        'manual' => {
+          source: 'userProvided',
+          dimensions: 3
+        }
+      }
+    ).await
+
+    new_index.add_documents(documents).await
+
+    response = new_index.search_similar_documents('287947')
+
+    expect(response['hits']).not_to be_empty
+    expect(response['estimatedTotalHits']).not_to be_nil
+  end
+end