Elasticsearch: Reindex to remove title completion

We implemented search_as_you_type for merge request title completion
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167432, but the
production performance was not good.

We are removing the search_as_you_type field during the same milestone 17.5, so
we can skip the reindexing for self-managed instances.

Changelog: removed
EE: true

ee/elastic/docs/20240920154436_reindex_merge_requests_for_title_completion.yml → ee/elastic/docs/20241002103536_reindex_merge_requests_for_title_completion.yml

 ---
 name: ReindexMergeRequestsForTitleCompletion
-version: '20240920154436'
+version: '20241002103536'
 description: Reindex merge requests for title completion
 group: group::global search
 milestone: '17.5'
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/166751
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167887
 obsolete: false
 marked_obsolete_by_url:
 marked_obsolete_in_milestone:
+skippable: true
+skip_condition: We implemented search_as_you_type for merge request title completion
+  https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167432, but the production performance was not good.
+  We will remove the search_as_you_type field during the same milestone 17.5, so we can skip the reindexing for
+  self-managed instances.

ee/elastic/migrate/20240920154436_reindex_merge_requests_for_title_completion.rb → ee/elastic/migrate/20241002103536_reindex_merge_requests_for_title_completion.rb

 # frozen_string_literal: true
 
 class ReindexMergeRequestsForTitleCompletion < Elastic::Migration
-  space_requirements!
+  skip_if -> { !Gitlab::Saas.feature_available?(:advanced_search) }
 
   def migrate
     Elastic::ReindexingTask.create!(targets: %w[MergeRequest], options: { skip_pending_migrations_check: true })
@@ -10,8 +10,4 @@ def migrate
   def completed?
     true
   end
-
-  def space_required_bytes
-    3 * helper.index_size_bytes(index_name: MergeRequest.index_name)
-  end
 end

ee/lib/elastic/latest/config.rb

@@ -31,10 +31,6 @@ module Config
                 tokenizer: 'standard',
                 filter: %w[word_delimiter_graph_filter asciifolding lowercase stemmer flatten_graph remove_duplicates]
               },
-              title_completion_analyzer: {
-                tokenizer: 'standard',
-                filter: %w[lowercase stop]
-              },
               default: {
                 tokenizer: 'standard',
                 filter: %w[lowercase stemmer]

ee/lib/elastic/latest/merge_request_config.rb

@@ -21,8 +21,7 @@ module MergeRequestConfig
         indexes :id, type: :integer
         indexes :iid, type: :integer
 
-        indexes :title, type: :text, index_options: 'positions', analyzer: :title_analyzer,
-          fields: { completion: { type: :search_as_you_type, analyzer: :title_completion_analyzer } }
+        indexes :title, type: :text, index_options: 'positions', analyzer: :title_analyzer
         indexes :description, type: :text, index_options: 'positions', analyzer: :code_analyzer
         indexes :state, type: :keyword
         indexes :project_id, type: :integer

ee/spec/elastic/migrate/20240920154436_reindex_merge_requests_for_title_completion_spec.rb → ee/spec/elastic/migrate/20241002103536_reindex_merge_requests_for_title_completion_spec.rb

 # frozen_string_literal: true
 
 require 'spec_helper'
-require File.expand_path('ee/elastic/migrate/20240920154436_reindex_merge_requests_for_title_completion.rb')
+require File.expand_path('ee/elastic/migrate/20241002103536_reindex_merge_requests_for_title_completion.rb')
 
 RSpec.describe ReindexMergeRequestsForTitleCompletion, feature_category: :global_search do
-  let(:version) { 20240920154436 }
+  let(:version) { 20241002103536 }
   let(:migration) { described_class.new(version) }
 
   it 'does not have migration options set', :aggregate_failures do
@@ -26,18 +26,4 @@
       expect(migration.completed?).to eq(true)
     end
   end
-
-  describe '#space_required_bytes' do
-    let(:helper) { ::Gitlab::Elastic::Helper.default }
-    let(:space_required_bytes) { migration.space_required_bytes }
-
-    before do
-      allow(::Gitlab::Elastic::Helper).to receive(:default).and_return(helper)
-      allow(helper).to receive(:index_size_bytes).with(index_name: MergeRequest.index_name).and_return(1_000)
-    end
-
-    it 'returns space required' do
-      expect(space_required_bytes).to eq(3_000)
-    end
-  end
 end