1 files changed, 36 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index 4c8db8a2d5..831bfa2df3 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -28,6 +28,42 @@ module ActiveRecord
           options[:null] = true if options[:null].nil?
           super
         end
+
+        def index_exists?(table_name, column_name, options = {})
+          column_names = Array(column_name).map(&:to_s)
+          options[:name] =
+            if options.key?(:name).present?
+              options[:name].to_s
+            else
+              index_name(table_name, column: column_names)
+            end
+          super
+        end
+
+        def remove_index(table_name, options = {})
+          index_name = index_name_for_remove(table_name, options)
+          execute "DROP INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)}"
+        end
+
+        private
+
+        def index_name_for_remove(table_name, options = {})
+          index_name = index_name(table_name, options)
+
+          unless index_name_exists?(table_name, index_name, true)
+            if options.is_a?(Hash) && options.has_key?(:name)
+              options_without_column = options.dup
+              options_without_column.delete :column
+              index_name_without_column = index_name(table_name, options_without_column)
+
+              return index_name_without_column if index_name_exists?(table_name, index_name_without_column, false)
+            end
+
+            raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' does not exist"
+          end
+
+          index_name
+        end
       end
 
       class V4_2 < V5_0