Move the logic to a concern

app/models/user.rb

@@ -5,6 +5,7 @@ class User < ActiveRecord::Base
 
   include Gitlab::ConfigHelper
   include Gitlab::CurrentSettings
+  include Gitlab::SQL::Pattern
   include Avatarable
   include Referable
   include Sortable
@@ -303,7 +304,7 @@ class User < ActiveRecord::Base
     # Returns an ActiveRecord::Relation.
     def search(query)
       table   = arel_table
-      pattern = Gitlab::SQL::Pattern.new(query).to_sql
+      pattern = User.to_pattern(query)
 
       order = <<~SQL
         CASE

lib/gitlab/sql/pattern.rb

 module Gitlab
   module SQL
-    class Pattern
-      MIN_CHARS_FOR_PARTIAL_MATCHING = 3
-
-      attr_reader :query
+    module Pattern
+      extend ActiveSupport::Concern
 
-      def initialize(query)
-        @query = query
-      end
+      MIN_CHARS_FOR_PARTIAL_MATCHING = 3
 
-      def to_sql
-        if exact_matching?
-          sanitized_query
+      class_methods do
+        def to_pattern(query)
+          if exact_matching?(query)
+            sanitize_sql_like(query)
           else
-          "%#{sanitized_query}%"
+            "%#{sanitize_sql_like(query)}%"
           end
         end
 
-      def exact_matching?
-        !partial_matching?
+        def exact_matching?(query)
+          query.length < MIN_CHARS_FOR_PARTIAL_MATCHING
         end
 
-      def partial_matching?
-        @query.length >= MIN_CHARS_FOR_PARTIAL_MATCHING
+        def partial_matching?(query)
+          query.length >= MIN_CHARS_FOR_PARTIAL_MATCHING
         end
-
-      def sanitized_query
-        # Note: ActiveRecord::Base.sanitize_sql_like is a protected method
-        ActiveRecord::Base.__send__(:sanitize_sql_like, query)
       end
     end
   end

spec/lib/gitlab/sql/pattern_spec.rb

 require 'spec_helper'
 
 describe Gitlab::SQL::Pattern do
-  describe '#to_sql' do
-    subject(:to_sql) { described_class.new(query).to_sql }
+  describe '#to_pattern' do
+    subject(:to_pattern) { User.to_pattern(query) }
 
     context 'when a query is shorter than 3 chars' do
       let(:query) { '12' }
 
       it 'returns exact matching pattern' do
-        expect(to_sql).to eq('12')
+        expect(to_pattern).to eq('12')
       end
     end
 
@@ -16,7 +16,7 @@ describe Gitlab::SQL::Pattern do
       let(:query) { '_2' }
 
       it 'returns sanitized exact matching pattern' do
-        expect(to_sql).to eq('\_2')
+        expect(to_pattern).to eq('\_2')
       end
     end
 
@@ -24,7 +24,7 @@ describe Gitlab::SQL::Pattern do
       let(:query) { '123' }
 
       it 'returns partial matching pattern' do
-        expect(to_sql).to eq('%123%')
+        expect(to_pattern).to eq('%123%')
       end
     end
 
@@ -32,7 +32,7 @@ describe Gitlab::SQL::Pattern do
       let(:query) { '_23' }
 
       it 'returns partial matching pattern' do
-        expect(to_sql).to eq('%\_23%')
+        expect(to_pattern).to eq('%\_23%')
       end
     end
 
@@ -40,7 +40,7 @@ describe Gitlab::SQL::Pattern do
       let(:query) { '1234' }
 
       it 'returns partial matching pattern' do
-        expect(to_sql).to eq('%1234%')
+        expect(to_pattern).to eq('%1234%')
       end
     end
 
@@ -48,7 +48,7 @@ describe Gitlab::SQL::Pattern do
       let(:query) { '_234' }
 
       it 'returns sanitized partial matching pattern' do
-        expect(to_sql).to eq('%\_234%')
+        expect(to_pattern).to eq('%\_234%')
       end
     end
   end